| 1. |
- Ai, Songyuan, et al.
(författare)
-
Ab Initio Calculations on Elastic Properties of IF Steel Matrix Phase at High Temperature Based on Lattice Expansion Theory
- 2020
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:2
-
Tidskriftsartikel (refereegranskat)abstract
- Elucidating the evolution law of the elastic properties of the matrix phase is of great significance for the control of steel properties and quality during continuous casting and subsequent heat treatment. In this paper, thermal expansion experiments and ab initio calculations are used to study the elastic properties of the interstitial free (IF) steel matrix phase in different magnetic states and crystal structures. The results show that the bulk modulus B and the tetragonal shear elastic constant C' for the entire temperature range decrease with increasing temperature, but C-44 is the opposite. While from paramagnetic (PM) to ferromagnetic (FM) state, C'(C-44) have changed similar to 188% (similar to 27%), B increases by similar to 55% during the crystal structure change (fcc -> bcc). With the FM to PM state, the Zener anisotropy parameter increases sharply, and Young's modulus decreases significantly in the [001] direction; the maximum difference is similar to 76 GPa. The evolution rate of average Young's modulus in single bcc-phase FM (fcc-phase PM) range reaches similar to 5.5(similar to 5.6) x 10(-2) GPa K-1. The research provides an effective method for ab initio calculation of the elastic properties of interstitial free and ultra-low carbon steels at high temperature, also furnishing a basis for the application of ab initio calculations to the high temperature performance of steel materials.
|
|
| 2. |
- Ai, S., et al.
(författare)
-
Ab Initio Study on Continuous Evolution of Mechanical Properties in Phase-Transition Region of Low-Carbon Steel
- 2020
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X.
-
Tidskriftsartikel (refereegranskat)abstract
- To control steel quality during continuous casting and subsequent heat treatment, an understanding of the evolution laws of mechanical properties during the austenite transition and the underlying mechanisms is of importance. Herein, the peak separation method is used to investigate the expansion behaviors in low-carbon steel. And the elastic properties of the matrix phase are calculated using the exact muffin-tin orbitals (EMTO) method. A continuous evolution model of high-temperature properties in the phase-transition region is established for ab initio data and experimental results. The evolution laws of the tetragonal shear elastic constant C′ and Young's modulus E agree well with that of the high-temperature strength. The critical temperature for ductility to brittleness is 850 °C. The matrix phase exhibits significantly brittleness character and increases slightly with decreasing temperature in single-phase paramagnetic (PM) γ-Fe region. The straightening zone temperature should be controlled above 950 °C to avoid cracks. In the austenite transition region, the drop rate of the magnetic moment reaches 18.90%. The findings suggest that the evolution law of mechanical properties of steels can be predicted from the elastic properties, especially during the austenite transition process, providing a basis for the prediction of material properties using ab initio methods.
|
|
| 3. |
- Ai, S. -Y, et al.
(författare)
-
High-temperature strength of l245mb slab and elastic properties of iron matrix
- 2019
-
Ingår i: Kang T'ieh/Iron and Steel. - : Chinese Society for Metals. - 0449-749X. ; 54:8, s. 194-201
-
Tidskriftsartikel (refereegranskat)abstract
- It‘s important to understand the evolution of high-temperature properties of slabs from the microscopic structure and the macroscopic structure, which is of great significance to the performance and quality control of slabs. The variation of the high-temperature strength of the L245MB slab with the temperature was measured by the hot tensile test technique with the Gleeble system. For the Fe matrix phase, which was under different crystal structures and magnetic states, the EMTO first-principles method was used to calculate the bulk modulus B, the single-crystal elastic constants c’ and c44, the polymorphic Young's modulus E, and the evolution of the system magnetic moment μ with temperature. The results showed that the cooling rate had little effect on the high-temperature strength evolution of the slab. The high-temperature strength took a transition near Ae3 and TC temperature, with a "platform" presented, where the average evolution rate of tensile strength was 0.008 Mpa/℃ and the yield strength was 0.076 Mpa/℃. The thermoplasticity of the slab had a different degree of decline in the temperature range of TC~Ae3, and the reduction of the area was the smallest at about 800℃, which was 59.02%~62.79%. The temperature range of ductility trough increased with the cooling rate increasing, and the surface temperature of the straightening zone should be controlled above 850 ℃ to avoid the crack generation. The elastic properties of the Fe matrix phase changed with the change of the magnetic state and the crystal structure. The transformation of the magnetic state had a greater influence on c’, c44, E, and the transformation of the crystal structure had a greater influence on B. During the transformation of FM to PM, c’ and E decreased by 64.09% and 10.33%, c44 increased by 57.82%, and B decreased by 34.38% with the change of bcc to fcc structure. The relationship between the evolution of single crystal elastic constant c’, polycrystalline Young's modulus E and the high-temperature strength of the slab were analyzed. It provides an idea for analyzing the macroscopic performance of the slab from the microstructural parameters of the crystal structure, which is a basis for the research and application of the first principles method in the high-temperature mechanical properties of steel materials.
|
|
| 4. |
- Chai, Guocai, 1956-, et al.
(författare)
-
Roles of Nitrogen on TWIP in Advanced Austenitic Stainless Steels
- 2022
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X.
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of nitrogen on the mechanical properties of two high Ni containing advanced austenitic stainless steels with low stacking fault energies is investigated. The results show that increase of nitrogen content greatly increases both strength and elongation of the steel at the same time. At the cryogenic temperature, the steels show a twin induced plasticity behavior. Ab initio calculations indicate that the increase of nitrogen slightly increases the stacking fault energy and consequently the critical shear stress for twin initiation in the steel. However, addition of nitrogen significantly increases the flow stress. This leads to a smaller critical strain for twin initiation and promotes deformation twinning in the high nitrogen steel. This is confirmed by the microstructure investigation. Deformation in steels is a competitive process between slip and twinning. Dislocation slip is dominant at low strain range, but formation of stacking fault and twinning become important in the later stages of deformation. At cryogenic temperature, it is mainly deformation twinning. The influence of nitrogen addition on magnetic property and its effect on deformation twinning are also discussed. The present study increases the understanding for the development of high-performance and low-cost advanced austenitic stainless steels.
|
|
| 5. |
- Choi, Young Won, et al.
(författare)
-
Density Functional Theory Description of Paramagnetic Hexagonal Close-Packed Iron
- 2022
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:4
-
Tidskriftsartikel (refereegranskat)abstract
- The hexagonal close-packed (hcp) phase of iron is unstable under ambient conditions. The limited amount of existing experimental data for this system has been obtained by extrapolating the parameters of hcp Fe-Mn alloys to pure Fe. On the theory side, most density functional theory (DFT) studies on hcp Fe have considered non-magnetic or ferromagnetic states, both having limited relevance in view of the current understanding of the system. Here, we investigate the equilibrium properties of paramagnetic hcp Fe using DFT modelling in combination with alloy theory. We show that the theoretical equilibrium c/a and the equation of state of hcp Fe become consistent with the experimental values when the magnetic disorder is properly accounted for. Longitudinal spin fluctuation effects further improve the theoretical description. The present study provides useful data on hcp Fe at ambient and hydrostatic pressure conditions, contributing largely to the development of accurate thermodynamic modelling of Fe-based alloys.
|
|
| 6. |
- Choi, Young Won, et al.
(författare)
-
Predicting the stacking fault energy of austenitic Fe-Mn-Al (Si) alloys
- 2020
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- Aluminum and silicon are common alloying elements for tuning the stacking fault energy (SFE) of high Mn steels. Today the theoretical investigations on the Fe-Mn-Al/Si systems using Density Functional Theory (DFT) are very scarce. In the present study, we employ a state-of-the-art longitudinal spin fluctuations (LSFs) model in combination with DFT for describing the magnetic effects in Fe-Mn based alloys at finite temperature. We find that the traditional DFT-floating spin results fail to explain the experimental trends. However, the DFT-LSFs approach properly captures the Al-induced increase and Si-induced decrease of the SFE of the base alloy in line with the room-temperature observations. This finding highlights the importance of LSFs in describing the Al/Si effects on the SEE of Fe-Mn based alloys. We point out that the effects of the non-magnetic Al and Si additions on the SEE are in fact determined by the magnetic state of the host matrix. In addition, we estimate the role of carbon addition in the alloying effects of Al and Si. The present results provide a convenient pathway to access the important mechanical parameters for designing advanced high-strength alloys.
|
|
| 7. |
- Dastanpour Hosseinabadi, Esmat, et al.
(författare)
-
Investigation of the metastable spinodally decomposed magnetic CrFe-rich phase in Al doped CrFeCoNi alloy
- 2023
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 939
-
Tidskriftsartikel (refereegranskat)abstract
- We have conducted an in-depth study of the magnetic phase due to a spinodal decomposition of the BCC phase of a CrFe-rich composition. This magnetic phase is present after casting (arc melting) or water quenching after annealing at 1250 degrees C for 24 h but is entirely absent after annealing in the interval 900-1100 degrees C for 24 h. Its formation is favored in the temperature interval ca 450-550 degrees C and loses magnetization above 640 degrees C. This ferromagnetic-paramagnetic transition is due to a structural transformation from ferromagnetic BCC into paramagnetic sigma and FCC phases. The conclusion from measurements at different heating rates is that both the transformation leading to the increase of the magnetization due to the spinodal decomposition of the parent phase and the vanishing magnetization at 640 degrees C are diffusion controlled. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
|
|
| 8. |
|
|
| 9. |
- Dong, Zhihua, et al.
(författare)
-
Computation of Phase Fractions in Austenite Transformation with the Dilation Curve for Various Cooling Regimens in Continuous Casting
- 2016
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 47:3, s. 1553-1564
-
Tidskriftsartikel (refereegranskat)abstract
- A concise model is applied to compute the microstructure evolution of austenite transformation by using the dilation curve of continuously cast steels. The model is verified by thermodynamic calculations and microstructure examinations. When applying the model, the phase fractions and the corresponding transforming rates during austenite transformation are investigated at various cooling rates and chemical compositions. In addition, ab initio calculations are performed for paramagnetic body-centered-cubic Fe to understand the thermal expansion behavior of steels at an atomic scale. Results indicate that by increasing the cooling rate, the final volume fraction of ferrite/pearlite will gradually increase/decrease with a greater transforming rate of ferrite. The ferrite fraction increases after austenite transformation with lowering of the carbon content and increasing of the substitutional alloying fractions. In the austenite transformation, the thermal expansion coefficient is sequentially determined by the forming rate of ferrite and pearlite. According to the ab initio theoretical calculations for the single phase of ferrite, thermal expansion emerges from magnetic evolution and lattice vibration, the latter playing the dominant role. The theoretical predictions for volume and thermal expansion coefficient are in good agreement with the experimental data.
|
|
| 10. |
- Dong, Zhihua, et al.
(författare)
-
Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels
- 2015
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 46:4, s. 1885-1894
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 degrees C min(-1) to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe, Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe. (C) The Minerals, Metals & Materials Society and ASM International 2015
|
|
| 11. |
- Dong, Zhihua, et al.
(författare)
-
Elastic properties of paramagnetic austenitic steel at finite temperature : Longitudinal spin fluctuations in multicomponent alloys
- 2017
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 96:17
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a first-principles framework for longitudinal spin fluctuations (LSFs) in disordered paramagnetic (PM) multicomponent alloy systems and apply it to investigate the influence of LSFs on the temperature dependence of two elastic constants of PM austenitic stainless steel Fe15Cr15Ni. The magnetic model considers individual fluctuating moments in a static PM medium with first-principles-derived LSF energetics in conjunction with describing chemical disorder and randomness of the transverse magnetic component in the single-site alloy formalism and disordered local moment (DLM) picture. A temperature-sensitive mean magnetic moment is adopted to accurately represent the LSF state in the elastic-constant calculations. We make evident that magnetic interactions between an LSF impurity and the PM medium are weak in the present steel alloy. This allows gaining accurate LSF energetics and mean magnetic moments already through a perturbation from the static DLM moments instead of a tedious self-consistent procedure. We find that LSFs systematically lower the cubic shear elastic constants c' and c(44) by similar to 6 GPa in the temperature interval 300-1600 K, whereas the predominant mechanism for the softening of both elastic constants with temperature is the magneto-volume coupling due to thermal lattice expansion. We find that non-negligible local magnetic moments of Cr and Ni are thermally induced by LSFs, but they exert only a small influence on the elastic properties. The proposed framework exhibits high flexibility in accurately accounting for finite-temperature magnetism and its impact on the mechanical properties of PM multicomponent alloys.
|
|
| 12. |
- Dong, Zhihua, et al.
(författare)
-
Finite temperature magnetic properties of CrxCoyNi100-x-y medium entropy alloys from first principles
- 2019
-
Ingår i: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 171, s. 78-82
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic structure of polymorphic Cr-Co-Ni medium entropy alloys is investigated as a function of temperature and chemical composition by ab initio calculations. Besides the thermal lattice expansion, the longitudinal spin fluctuations (LSFs) are accounted for in determining the magnetic state at finite temperature. We show that sizable local magnetic moments persist on all alloy components in the paramagnetic state for both face-centered cubic and hexagonal close-packed structures, and each alloy species exhibits particular temperature and concentration dependencies. The crucial role of LSFs for the finite temperature magnetic state and its impact on the temperature dependent elastic parameters are demonstrated.
|
|
| 13. |
|
|
| 14. |
- Dong, Zhihua, et al.
(författare)
-
Influence of Mn content on the intrinsic energy barriers of paramagnetic FeMn alloys from longitudinal spin fluctuation theory
- 2019
-
Ingår i: International journal of plasticity. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0749-6419 .- 1879-2154. ; 119, s. 123-139
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations were performed to investigate the influence of Mn content on the intrinsic energy barriers (IEBs) of paramagnetic FeMn alloys with face-centered cubic (fcc) structure. The IEBs were derived from the free energies accounting for longitudinal spin fluctuations (LSFs). LSFs are demonstrated to be important for the quantitative description of IEBs and their alloying dependencies at finite temperature. The unstable stacking and unstable twinning fault energies of the fcc phase slightly decrease with Mn content, whereas the intrinsic stacking fault energy (gamma(fcc)(isf)) is predicted to monotonically increase. This latter finding contradicts the experimentally reported, local minimum of gamma(isf) in the fcc/hexagonal close-packed (hcp) coexistence region. The partitioning of Mn during the fcc/hcp phase transition is proposed to reconcile theory and experiment. Both temperature and impurities ([C] and Cr) hardly influence the monotonic concentration dependence of gamma(fcc)(isf) but considerably alter the magnitude. The fcc/hcp interfacial energy is nearly independent of Mn concentration in contrast to the parabolic dependence predicted in thermodynamic modeling. In contrast to the fcc phase, the estimated intrinsic stacking fault energy of the ideal hcp structure monotonically decreases with Mn content and temperature. A high twinnability is predicted at 450 K within the stability field of the paramagnetic fcc Fe-Mn alloys.
|
|
| 15. |
- Dong, Zhihua, et al.
(författare)
-
Invariant plastic deformation mechanism in paramagnetic nickel-iron alloys
- 2021
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:14
-
Tidskriftsartikel (refereegranskat)abstract
- The Invar anomaly is one of the most fascinating phenomena observed in magnetically ordered materials. Invariant thermal expansion and elastic properties have attracted substantial scientific attention and led to important technological solutions. By studying planar faults in the high-temperature magnetically disordered state of Ni1-cFec, here we disclose a completely different anomaly. An invariant plastic deformation mechanism is characterized by an unchanged stacking fault energy with temperature within wide concentration and temperature ranges. This anomaly emerges from the competing stability between the face-centered cubic and hexagonal close-packed structures and occurs in other paramagnetic or nonmagnetic systems whenever the structural balance exists. The present findings create a platform for tailoring high-temperature properties of technologically relevant materials toward plastic stability at elevated temperatures.
|
|
| 16. |
- Dong, Zhihua, et al.
(författare)
-
Longitudinal spin fluctuation contribution to thermal lattice expansion of paramagnetic Fe
- 2017
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:5
-
Tidskriftsartikel (refereegranskat)abstract
- Using an efficient first-principles computational scheme for paramagnetic body-centered cubic (bcc) and face-centered cubic (fcc) Fe, we investigate the impact of thermal longitudinal spin fluctuations (LSFs) on the thermal lattice expansion. The equilibrium physical parameters are derived from the self-consistent Helmholtz free energy, in which the LSFs are considered within the adiabatic approximation and the anharmonic lattice vibration effect is included using the Debye-Gruneisen model taking into account the interplay between thermal, magnetic, and elastic degrees of freedom. Thermal LSFs are energetically more favorable in the fcc phase than in the bcc one giving a sizable contribution to the linear thermal expansion of gamma-Fe. The present scheme leads to accurate temperature-dependent equilibriumWigner-Seitz radius, bulk modulus, and Debye temperature within the stability fields of the two phases and demonstrates the importance of thermal spin fluctuations in paramagnetic Fe.
|
|
| 17. |
- Dong, Zhihua, et al.
(författare)
-
MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 high entropy alloys for magnetocaloric refrigeration near room temperature
- 2021
-
Ingår i: Journal of Materials Science & Technology. - : Chinese Society of Metals. - 1005-0302. ; 79, s. 15-20
-
Tidskriftsartikel (refereegranskat)abstract
- High entropy alloys (HEAs) based on transition metals display rich magnetic characteristics, however attempts on their application in energy efficient technologies remain scarce. Here, we explore the magnetocaloric application for a series of MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 (0.8 < x < 1.1) HEAs by integrated theoretical and experimental methods. Both theory and experiment indicate the designed HEAs have the Curie temperature close to room temperature and is tunable with Mn concentration. A non-monotonic evolution is observed for both the entropy change and the relative cooling power with changing Mn concentration. The underlying atomic mechanism is found to primarily emerge from the complex impact of Mn on magnetism. Advanced magnetocaloric properties can be achieved by tuning Mn concentration in combination with controlling structural phase stability for the designed HEAs.
|
|
| 18. |
- Dong, Zhihua, et al.
(författare)
-
Plastic deformation modes in paramagnetic gamma-Fe from longitudinal spin fluctuation theory
- 2018
-
Ingår i: International journal of plasticity. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0749-6419 .- 1879-2154. ; 109, s. 43-53
-
Tidskriftsartikel (refereegranskat)abstract
- Using an efficient first-principles computational scheme, we calculate the intrinsic stacking fault energy (gamma(isf) ) and the unstable stacking fault energy (gamma(usf)) of paramagnetic gamma-Fe as a function of temperature. The formation energies are derived from free energies accounting for thermal longitudinal spin fluctuations (LSFs). LSFs are demonstrated to be important for the accurate description of the temperature-dependent magnetism, intrinsic and unstable stacking fault energies, and have a comparatively large effect on gamma(isf) of gamma-Fe. Dominated by the magneto-volume coupling at thermal excitations, gamma(isf) of gamma-Fe exhibits a positive correlation with temperature, while gamma(usf )declines with increasing temperature. The predicted stacking fault energy of gamma-Fe is negative at static condition, crosses zero around 540 K, and reaches 71.0 mJ m(-2) at 1373 K, which is in good agreement with the experimental value. According to the plasticity theory formulated in terms of the intrinsic and unstable stacking fault energies, twinning remains a possible deformation mode even at elevated temperatures. Both the large positive temperature slope of gamma(usf) and the predicted high-temperature twinning are observed in the case of austenitic stainless steels.
|
|
| 19. |
- Dong, Zhihua, et al.
(författare)
-
Strong temperature – Dependence of Ni -alloying influence on the stacking fault energy in austenitic stainless steel
- 2020
-
Ingår i: Scripta Materialia. - : Acta Materialia Inc. - 1359-6462 .- 1872-8456. ; 178, s. 438-441
-
Tidskriftsartikel (refereegranskat)abstract
- Using ab initio alloy theory, we calculate the impact of Ni on the stacking fault energy in austenitic stainless steel as a function of temperature. We show that the influence of Ni strongly couples with temperature. While a positive effect on the stacking fault energy is obtained at ambient temperature, the opposite negative effect is disclosed at elevated temperatures. An important rationale behind is demonstrated to be the variation of magneto-volume coupling induced by Ni alloying. The alloy influence on the finite temperature evolution of Ni impact is evaluated for elements Cr, Mo and N.
|
|
| 20. |
- Dong, Zhihua
(författare)
-
Temperature dependent mechanical properties of as-cast steels : Experimental and theoretical studies
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The temperature-dependent mechanical properties of steels are important to avoid processing defects, to understand and to improve the high-temperature performance. At the same time, having access to thermal properties gives us opportunity to assess the first-principles theoretical predictions at elevated temperatures. These properties are directly bound up with the performance of individual phase and also the evolving microstructure states at different thermalmechanical processes. In the present thesis, the temperature-dependent mechanical properties of continuously cast steels and iron are investigated using experimental and theoretical methods. Experimental studies are performed centering on the influence of thermal cycles occurring in secondary cooling.The temperature reversion in secondary cooling makes the hot ductility trough occurring at higher temperatures with greater depth. Increasing the reversion rate, the low temperature end of the ductility trough slightly extends to lower temperatures. As indicated by microstructure examinations, the intergranular fracture contributed from the thin film-like ferrite and (Fe,Mn)S particles slightly changes with the varying thermal cycles; however, the widmanstatten ferrite observed in the temperature reversion process seriously deteriorates the ductility. Due to the temperature reversion process, the peak stress slightly declines and the peak of strain to peak stress moves to higher temperatures. On the other hand, the sequential formations of ferrite and pearlite in the austenite transformation are indicated by two distinct peaks on the thermal expansion coefficient. By applying the developed concise model, the volume fractions of ferrite, pearlite, and austenite are quantitatively monitored in the phase transformation. Either increasing the cooling rate or the content of austenite stabilizing atoms Ni and Cu, the austenite transformation occurs at relatively low temperatures and indicates a greater phase transformation rate for both ferrite and pearlite. In addition, the final fraction of ferrite/pearlite increases/decreases with increasing the cooling rate, increasing the alloying atoms like Ni, Cr and Cu or lowering the carbon content.The temperature dependence of the polycrystalline Young’s modulus and the tetragonal shear modulus c0 of iron is predicted using ab initio calculations within the exact muffin-tin orbitals formalism. The dependence exhibits a good consistency with that of the peak stress observed in the experiments for the commercial steel. Despite the significant effects of magnetic sate and crystal structure on the elastic property of iron, the magneto-volume coupling primarily determines the temperature dependence for the single phase. In contrast, the dominant role of the volume expansion is observed for both the paramagnetic (PM) face centered cubic (fcc) and body centered cubic (bcc) Fe, although they show different magneto-elastic behaviors. Based on the theoretically predicted thermal expansion for PM bcc Fe, both the lattice vibrations and the magnetic evolution contribute to the thermal expansion, and the former is dominant.
|
|
| 21. |
- Dong, Zhihua, et al.
(författare)
-
Thermal spin fluctuation effect on the elastic constants of paramagnetic Fe from first principles
- 2015
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 92:22
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the impact of longitudinal thermal spin fluctuations on the temperature dependence of the elastic constants of paramagnetic body-centered-cubic (bcc) and face-centered-cubic (fcc) Fe. Based on a series of constrained local magnetic moment calculations, the spin fluctuation distribution is established using Boltzmann statistics and involving the Jacobian weight, and a temperature-dependent quadratic mean moment is introduced that accurately represents the spin fluctuation state as a function of temperature. We show that with increasing temperature, c' and c(44) for the fcc phase and c(44) for the bcc phase decrease at different rates due to different magnetoelastic coupling strengths. In contrast, c' in the bcc phase exhibits relatively high thermal stability. Longitudinal thermal spin fluctuations diminish the softening of both elastic constants in either phase and have comparatively large contributions in the fcc phase. In both bcc and fcc Fe, c(44) has a larger temperature factor than c'. On the other hand, c' is more sensitive to the longitudinal thermal spin fluctuations, which balance the volume-induced softening by 21.6% in fcc Fe.
|
|
| 22. |
- Dong, Zhihua, et al.
(författare)
-
Thermal spin fluctuations in CoCrFeMnNi high entropy alloy
- 2018
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- High entropy alloys based on 3d transition metals display rich and promising magnetic characteristics for various high-technology applications. Understanding their behavior at finite temperature is, however, limited by the incomplete experimental data for single-phase alloys. Here we use first-principles alloy theory to investigate the magnetic structure of polymorphic CoCrFeMnNi in the paramagnetic state by accounting for the longitudinal spin fluctuations (LSFs) as a function of temperature. In both face-centered cubic (fcc) and hexagonal close-packed (hcp) structures, the LSFs induce sizable magnetic moments for Co, Cr and Ni. The impact of LSFs is demonstrated on the phase stability, stacking fault energy and the fcc-hcp interfacial energy. The hcp phase is energetically preferable to the fcc one at cryogenic temperatures, which results in negative stacking fault energy at these conditions. With increasing temperature, the stacking fault energy increases, suppressing the formation of stacking faults and nano-twins. Our predictions are consistent with recent experimental findings.
|
|
| 23. |
- Dong, Zhihua, et al.
(författare)
-
Thermo-mechanical properties of Cr-Co-Ni alloys from longitudinal spin fluctuation theory
- 2021
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:8
-
Tidskriftsartikel (refereegranskat)abstract
- Accounting for longitudinal spin fluctuations in the paramagnetic state, we calculate elastic constants and stacking fault energy as a function of temperature and chemical composition for Cr-Co-Ni alloys. The longitudinal spin fluctuations are demonstrated to be important for the quantitative description of the thermo-mechanical properties and the corresponding chemical and temperature dependences. Replacing Ni with Cr and Co is found to yield opposite influence on the mechanical properties at finite temperature. A high thermal stability in plasticity is predicted in the low Cr regime in Cr-Co-Ni alloys, while a good thermal stability in elasticity can be achieved in the high Cr and low Co regime. The present advance in thermo-chemical-magnetic-property enhances the understanding required for an intelligent design of multicomponent alloys toward high-technology applications. Published under an exclusive license by AIP Publishing.
|
|
| 24. |
- Gui, Lintao, et al.
(författare)
-
Quantitative effects of phase transition on solute partition coefficient, inclusion precipitation, and microsegregation for high-sulfur steel solidification
- 2019
-
Ingår i: Journal of Materials Science & Technology. - : JOURNAL MATER SCI TECHNOL. - 1005-0302. ; 35:10, s. 2383-2395
-
Tidskriftsartikel (refereegranskat)abstract
- Segregation and inclusion precipitation are the common behaviours of steel solidification, which are resulted from the redistribution and diffusion of the solute elements at the solid-liquid interface. The effect of the phase transition of high-sulfur free-cutting steel is quantified in the present work for the solute partition coefficient (k(i)), inclusion precipitation, and microsegregation by establishing a coupling model of microsegregation and inclusion precipitation, wherein the quantified dependencies of k(i) in terms of temperature, phase and carbon temperature range and phase transition of high-sulfur steel that under different solidification paths and C contents were quite different, leading to differences in k(i) and eventually in microsegregation. k k(p), and k(s) were mainly affected by phase composition and k(si) was primarily by temperature, while k(mn) depended on both phase composition and temperature during solidification. Increasing the C content within the interval 0.07-0.48 wt%, the 'proportion of the delta phase maintained temperature region during solidification' (P-delta), k(p)(ave) and k(s)(ave) (k(i)(ave) the average value of the k(i) across the whole stages of solidification) decreased monotonically, whereas k phase composition and k(i), leading to the change in microsegregation. Such effect of the peritectic reaction was more significant at the last stage of solidification. When the P-delta was between 75% and 100% (corresponding to 0.07-0.16 wt% C), the solidification path resulted in a greater effect on the microsegregation of solutes C, P, and S because of the peritectic reaction. The microsegregation of solutes Mn and S were comprehensively influenced by k(Mn), k(s) and MnS precipitation as well. The studies would help reveal the solute redistribution at the solid-liquid interface, and improve the segregation of high-sulfur steel by controlling the solidification and precipitation in practice.
|
|
| 25. |
- Huang, He, et al.
(författare)
-
Critical stress for twinning nucleation in CrCoNi-based medium and high entropy alloys
- 2018
-
Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 149, s. 388-396
-
Tidskriftsartikel (refereegranskat)abstract
- The CrCoNi-based medium and high entropy alloys (MHEAs) have drawn much attention due to their exceptional mechanical properties at cryogenic temperatures. The twinning critical resolved shear stress (CRSS) is a fundamental parameter for evaluating the strength-ductility properties of MHEAs. Here we construct and apply an extended twinning nucleation Peierls-Nabarro (P-N) model to predict the twinning CRSSes of face-centered cubic (FCC) CrCoNi-based MHEAs. The order of the twinning CRSSes of the selected alloys is CrCoNi > CrCoNiMn > CrCoNiFe > CrCoNiFeMn and the values are 291, 277, 274 and 236 MPa, respectively. These theoretical predictions agree very well with the experimental twinning CRSSes of CrCoNi and CrCoNiFeMn accounting for 260 +/- 30 and 235 +/- 10 MPa, respectively and are perfectly consistent with the strength-ductility properties including yield stress, ultimate tensile stress and uniform elongation for fracture of the FCC CrCoNi-based MHEAs obtained at cryogenic temperatures. The present method offers a first-principle quantum-mechanical tool for optimizing and designing new MHEAs with exceptional mechanical properties.
|
|
| 26. |
- Huang, Shuo, et al.
(författare)
-
Magnetocaloric properties of melt-spun MnFe-rich high-entropy alloy
- 2021
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:14
-
Tidskriftsartikel (refereegranskat)abstract
- High-entropy functional materials are of great interest in materials science and engineering community. In this work, ab initio electronic structure calculations of the phase stability and magnetic transition temperature of AlxCr0.25MnFeCo0.25-yNiy (x = 0-0.5, y = 0-0.25) alloys were performed to screen for compositions showing promising magnetocaloric properties in the vicinity of room temperature. The selected Al0.44Cr0.25MnFeCo0.05Ni0.2 alloy was synthesized via a rapid solidification technique and systematically characterized with respect to its structural and magnetocaloric properties. The results indicate that this alloy possesses a homogeneous microstructure based on an underlying body-centered cubic lattice and has a Curie temperature of & SIM;340 K. The temperature dependence of the adiabatic temperature change was evaluated using both direct and indirect methods. The ab initio-assisted design of 3d-metal-based high-entropy alloys, explored here, is intended to contribute to the development of magnetic refrigerators for room-temperature applications.
|
|
| 27. |
- Huang, Shou, et al.
(författare)
-
Thermo-elastic Properties of BCC Mn-rich High-entropy Alloy
- 2020
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 117:16
-
Tidskriftsartikel (refereegranskat)abstract
- We report a chemically disordered solid solution, Al0.6Cr0.2MnFe0.5Co0.3Ni0.5, based on a body-centered cubic underlying lattice with the measured Curie temperature of ∼380 K. First-principles alloy theory is employed to investigate the temperature-dependent free energy, elastic constants, and coefficient of thermal expansion at the ferromagnetic and paramagnetic states. Theory and experiment are found to strengthen each other, and the results indicate that the magnetic state has a strong impact on the thermo-elastic properties of the considered alloy. The present advance in the thermo-magneto-elasticity enhances the understanding required for controlling the magnetic and mechanical response of multi-component systems.
|
|
| 28. |
- Huang, Shuo, et al.
(författare)
-
Vibrational entropy-enhanced magnetocaloric effect in Mn-rich high-entropy alloys
- 2021
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 119:8
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the AlxCr0.2MnFe0.5Co0.3Ni0.5 (0.3 <= x <= 0.7) high-entropy alloys by combining experimental and theoretical techniques. X-ray diffraction and magnetization measurements indicate that Al alters the crystal structure and the entropy change upon magnetization-demagnetization while keeping the Curie temperature almost unchanged. First-principles calculations of the vibrational, magnetic, electronic, and configurational entropies show that the leading entropy change is due to the magnetic and vibrational degrees of freedom. The presence of the body-centered-cubic phase, showing a sizable elastic softening upon magnetic transition, brings about the substantial magnetocaloric effect in this family of alloys.
|
|
| 29. |
- Li, Changle, 1992-, et al.
(författare)
-
Critical assessment of Co-Cu phase diagram from first-principles calculations
- 2020
-
Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 102:18
-
Tidskriftsartikel (refereegranskat)abstract
- Using first-principles alloy theory, we perform a systematic study of the Co-Cu phase diagram. Calculations are carried out for ferromagnetic and paramagnetic Co1-xCux solid solutions with face-centered-cubic (fcc) crystal structure. We find that the equilibrium volumes and magnetic states are crucial for a quantitative description of the thermodynamics of the Co-Cu system at temperatures up to 1400 K. In particular, the paramagnetic state of Cu-rich alloys with persisting local magnetic moments is shown to be responsible for the solubility of a small amount of Co in fcc Cu whereas the excess entropy in the ferromagnetic Co-rich region critically depends on the adopted lattice parameters. None of the common local or semilocal density functional theory approximations have the necessary accuracy for the lattice parameters when compared to the experimental data. The predicted ab initio Co-Cu phase diagram is in good agreement with the measurements and CALPHAD data, making it possible to gain a deep insight into the various contributions to the Gibbs free energy. The present study provides an atomic-level description of the thermodynamic quantities controlling the limited mutual solubility of Co and Cu and highlights the importance of high-temperature magnetism.
|
|
| 30. |
- Liu, Tao, et al.
(författare)
-
Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior
- 2019
-
Ingår i: Journal of Iron and Steel Research International. - : SPRINGER. - 1006-706X .- 2210-3988. ; 26:2, s. 162-172
-
Tidskriftsartikel (refereegranskat)abstract
- A combined model to predict austenite grains growth of titanium micro-alloyed as-cast steel during reheating process was established. The model involves the behaviors of austenite grains growth in continuous heating process and isothermal soaking process, and the variation of boundary pinning efficiency caused by the dissolution and coarsening kinetics of second-phase particles was also considered into the model. Furthermore, the experimental verifications were performed to examine the prediction power of the model. The results revealed that the mean austenite grains size increased with the increase in reheating temperature and soaking time, and the coarsening temperature of austenite grains growth was 1423K under the current titanium content. In addition, the reliability of the predicted results in continuous heating process was validated by continuous heating experiments. Moreover, an optimal regression expression of austenite grains growth in isothermal soaking process was obtained based on the experimental results. The compared results indicated that the combined model in conjunction with precipitates dissolution and coarsening kinetics had good reliability and accuracy to predict the austenite grains growth of titanium micro-alloyed casting steel during reheating process.
|
|
| 31. |
- Nordström, Joakim, 1971-, et al.
(författare)
-
Temperature study of deformation twinning behaviour in Nickel-base Superalloy 625
- 2024
-
Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936.
-
Tidskriftsartikel (refereegranskat)abstract
- Deformation behaviour in the Nickel-base superalloy 625 has been studied by tensile testing at four temperatures: 295, 223, 173 and 77 K. The microstructure has been investigated using TEM, FIB-SEM, EBSD and ECCI techniques. Deformation in the alloy turns out to be a competitive course of events between at least two deformation mechanisms, namely dislocation slip and deformation twinning. Slip is the predominant deformation mechanism at higher temperatures. While at 77 K, deformation induced twinning gives an extra degree of freedom as one of the main deformation mechanisms, i.e., the material shows a twin induced plasticity, TWIP, behaviour. Ab initio calculations indicate that the influence of cryogenic/sub-zero temperatures on the stacking fault energy of this alloy can be limited and that the formation of deformation twins cannot be determined solely by the stacking fault energy. The results implies that it is the critical strain and strain hardening rate that influences the deformation twinning onset and twinning rate.
|
|
| 32. |
- Nordström, Joakim, 1971-, et al.
(författare)
-
Temperature study of deformation twinning behaviour in nickel-base Superalloy 625
- 2024
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 907
-
Tidskriftsartikel (refereegranskat)abstract
- Deformation behaviour in the Nickel-base superalloy 625 has been studied by tensile testing at four temperatures: 295, 223, 173 and 77 K. The microstructure has been investigated using TEM, FIB-SEM, EBSD and ECCI techniques. Deformation in the alloy turns out to be a competitive course of events between at least two deformation mechanisms, namely dislocation slip and deformation twinning. Slip is the predominant deformation mechanism at higher temperatures. While at 77 K, deformation induced twinning gives an extra degree of freedom as one of the main deformation mechanisms, i.e., the material shows a twin induced plasticity, TWIP, behaviour. Ab initio calculations indicate that the influence of cryogenic/sub-zero temperatures on the stacking fault energy of this alloy can be limited and therefore the formation of deformation twins cannot be determined solely by the stacking fault energy. The results implies that critical strain and strain hardening rate influences the deformation twinning onset and twinning rate.
|
|
| 33. |
- Sun, He, et al.
(författare)
-
Increased glacier melt enhances future extreme floods in the southern Tibetan Plateau
- 2024
-
Ingår i: Advances in Climate Change Research. - 1674-9278 .- 2524-1761.
-
Tidskriftsartikel (refereegranskat)abstract
- Mountainous areas are of special hydrological concern because topography and atmospheric conditions can result in large and sudden floods, posing serious risks to water-related safety in neighbouring countries. The Yarlung Zangbo (YZ) River basin is the largest river basin on the Tibetan Plateau (TP), but how floods will discharge in this basin and how the role of glacier melt in floods will change throughout the 21st-century under shared socioeconomic pathways scenarios (SSP2-4.5 and SSP5-8.5) remain unclear. Here, we comprehensively address this scientific question based on a well-validated large-scale glacier-hydrology model. The results indicate that extreme floods was projected to increase in the YZ basin, and was mainly reflected in increased duration (4–10 d per decade) and intensity (153–985 m3 s−1 per decade). Glacier runoff was projected to increase (2–30 mm per decade) throughout the 21st-century, but there was also a noticeable decrease or deceleration in glacier runoff growth in the late first half of the century under the SSP2-4.5, and in the latter half of the century under the SSP5-8.5. Glacier melt was projected to enhance the duration (12%–23%) and intensity (15%–21%) of extreme floods under both SSPs, which would aggravate the impact of future floods on the socioeconomics of the YZ basin. This effect was gradually overwhelmed by precipitation-induced floods from glacier areas to YZ outlet. This study takes the YZ basin as a projection framework example to help enrich the understanding of future flood hazards in basins affected by rainfall- or meltwater across the TP, and to help policy-makers and water managers develop future plans.
|
|
| 34. |
- Wang, Xiaohua, et al.
(författare)
-
Tacrolimus Causes Hypertension by Increasing Vascular Contractility via RhoA (Ras Homolog Family Member A)/ROCK (Rho-Associated Protein Kinase) Pathway in Mice
- 2022
-
Ingår i: Hypertension. - : Ovid Technologies (Wolters Kluwer Health). - 0194-911X .- 1524-4563. ; 79:10, s. 2228-2238
-
Tidskriftsartikel (refereegranskat)abstract
- Background: To provide tacrolimus is first-line treatment after liver and kidney transplantation. However, hypertension and nephrotoxicity are common tacrolimus side effects that limit its use. Although tacrolimus-related hypertension is well known, the underlying mechanisms are not. Here, we test whether tacrolimus-induced hypertension involves the RhoA (Ras homolog family member A)/ROCK (Rho-associated protein kinase) pathway in male C57Bl/6 mice. methods: Intra-arterial blood pressure was measured under anesthesia. The reactivity of renal afferent arterioles and mesenteric arteries were assessed in vitro using microperfusion and wire myography, respectively. Results: Tacrolimus induced a transient rise in systolic arterial pressure that was blocked by the RhoA/ROCK inhibitor Fasudil (12.0 +/- 0.9 versus 3.2 +/- 0.7; P<0.001). Moreover, tacrolimus reduced the glomerular filtration rate, which was also prevented by Fasudil (187 +/- 20 versus 281 +/- 8.5; P<0.001). Interestingly, tacrolimus enhanced the sensitivity of afferent arterioles and mesenteric arteries to Ang II (angiotensin II), likely due to increased intracellular Ca2+ mobilization and sensitization. Fasudil prevented increased Ang II-sensitivity and blocked Ca2+ mobilization and sensitization. Preincubation of mouse aortic vascular smooth muscle cells with tacrolimus activated the RhoA/ROCK/MYPT-1 (myosin phosphatase targeting subunit 1) pathway. Further, tacrolimus increased cytoplasmic reactive oxygen species generation in afferent arterioles (107 +/- 5.9 versus 163 +/- 6.4; P<0.001) and in cultured mouse aortic vascular smooth muscle cells (100 +/- 7.5 versus 160 +/- 23.2; P<0.01). Finally, the reactive oxygen species scavenger Tempol inhibited tacrolimus-induced Ang II hypersensitivity in afferent arterioles and mesenteric arteries. Conclusions: The RhoA/ROCK pathway may play an important role in tacrolimus-induced hypertension by enhancing Ang II-specific vasoconstriction, and reactive oxygen species may participate in this process by activating the RhoA/ROCK pathway.
|
|
| 35. |
- Wang, Yong, et al.
(författare)
-
Characterization and formation mechanism of non-metallic inclusions in single bcc-phase high entropy alloy
- 2023
-
Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 205
-
Tidskriftsartikel (refereegranskat)abstract
- This work aims to provide a fundamental study of inclusion characteristics in the single bcc-phase high entropy alloy (HEA), Mn-rich and Al-contained multicomponent system (Al-Cr-Mn-Fe-Co-Ni) was selected as the prototype alloy in this study. According to the differential thermal analysis (DTA) measurements, the solidus (TS) and liquidus (TL) temperatures of this alloy were in the range of 1225–1228 °C (1226 ± 2 °C) and 1268–1271 °C (1270 ± 2 °C), respectively. Non-metallic inclusions were investigated in a two-dimensional (2D) cross-section method as well as extracted by a three-dimensional (3D) electrolytic extraction method. It was found that AlN was the dominant inclusion phase, also a small amount of Al2O3 inclusions were observed. They formed in the liquid alloy and mostly presented as Al2O3-AlN agglomerates, where the size range of the AlN inclusions was larger than that of Al2O3. The theoretical calculation showed that AlN inclusion has a higher coagulation coefficient and collision rate than those of Al2O3 inclusions, which agrees well with the experimental observations. The inclusion characteristics of Al2O3 and AlN were closely related to the relative contents of O and N in the presence of high Al content in the alloy. The impurity elements of N and O were the key issues in controling the stable inclusion phase in high entropic alloy.
|
|
| 36. |
- Wang, Yong, et al.
(författare)
-
Inclusion Engineering in Medium Mn Steels : Effect of Hot-Rolling Process on the Deformation Behaviors of Oxide and Sulfide Inclusions
- 2022
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Nature. - 1073-5615 .- 1543-1916. ; 53:4, s. 2182-2197
-
Tidskriftsartikel (refereegranskat)abstract
- Medium Mn steel (MMS) is a new category of the third-generation advanced high strength steel (3rd AHSS) which is developed in the recent 1-2 decades due to a unique trade-off of strength and ductility. Thus, this steel grade has a wide application potential in different fields of industry. The current work provides a fundamental study of the effect of hot-rolling on the inclusion deformation inMMSincluding a varied 7 to 9 mass pctMn. Specifically, the deformation behavior of different types of inclusions (i.e., Mn(S,Se), liquid oxide (MnSiO3), MnAl2O4, and complex oxy-sulfide) was investigated. The results show that both MnSiO3 and Mn(S,Se) are soft inclusions which are able to be deformed during the hot-rolling process but MnAl2O4 does not. The aspect ratio of soft inclusions increases significantly from as-cast to hot-rolling conditions. When the maximum size of different inclusions is similar, Mn(S,Se) deforms more than MnSiO3 does. This is due to a joint influence of physical parameters including Young's modulus, coefficient of thermal expansion (α), etc. However, when the maximum size of one type of inclusion (e.g., MnSiO3) is much larger than another one (e.g., Mn(S,Se)), this maximum size of soft inclusions plays a dominant role than other factors. In addition, the deformation behavior of dual-phase inclusion depends on the major phase, i.e., either oxide or sulfide. Last but not least, empirical correlations between the reduction ratio of the thickness of plate, grain size, and aspect ratio of oxide and sulfide inclusions after hot-rolling are provided quantitatively. This work aims to contribute to the 'inclusion engineering' concept in the manufacturing of new generation AHSS.
|
|
| 37. |
- Zhang, Hualei, et al.
(författare)
-
Elastic properties of AlxCrMnFeCoNi (0 <= x <= 5) high-entropy alloys from ab initio theory
- 2018
-
Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 155, s. 12-22
-
Tidskriftsartikel (refereegranskat)abstract
- Using ab initio calculations, we investigate the elastic properties of paramagnetic AlxCrMnFeCoNi (0 <= x <= 5) high -entropy alloys (HEAs) in both body-centered cubic (bcc) and face-centered cubic (fcc) structures. Comparison with available experimental data demonstrates that the employed approach describes accurately the elastic moduli. The predicted lattice constants increase monotonously with Al addition, whereas the elastic parameters exhibit complex composition dependences. The elastic anisotropy is unusually high for both phases. The brittle/ductile transitions formulated in terms of Cauchy pressure and Pugh ratio become consistent only when the strong elastic anisotropy is accounted for. The negative Cauchy pressure of CrMnFeCoNi is due to the relatively low bulk modulus and C-12 elastic constant, which in turn are consistent with the relatively low cohesive energy. The present findings in combination with the experimental data suggest anomalous metallic character for the HEAs system. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
|
|
