| 1. |
- Aripov, G. R., et al.
(författare)
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The Study of Structural Changes in Homogenized High-Entropy Alloys
- 2021
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Ingår i: Physical Mesomechanics. - : Pleiades Publishing Ltd. - 1029-9599 .- 1990-5424. ; 24:6, s. 663-673
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates the effect of chemical composition on the microstructure and properties of cast high-entropy alloys, and optimal conditions for homogenization annealing. The investigation is performed on alloys of the following compositions: Fe22.5Ni22.5Cu22.5Co22.5Al10, Fe22.5Ni22.5Cu22.5Cr22.5Al10, and Fe22.5Ni22.5Cu22.5Mn22.5Al10 (shortly Fe22.5Ni22.5Cu22.5(Co, Cr or Mn)(22.5)Al-10), melted in an induction furnace with casting into a copper mold. The structural and phase changes in high-entropy alloys of different chemical composition are examined before and after homogenization annealing. The morphology of crystalline phases and microstructural evolution are analyzed experimentally. The strength characteristics of the alloys subjected to different homogenization annealing conditions are determined.
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| 2. |
- Churyumov, A. Yu., et al.
(författare)
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Effect of Nb Addition on Microstructure and Thermal and Mechanical Properties of Fe-Co-Ni-Cu-Cr Multiprincipal-Element (High-Entropy) Alloys in As-Cast and Heat-Treated State
- 2019
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Ingår i: JOM. - : SPRINGER. - 1047-4838 .- 1543-1851. ; 71:10, s. 3481-3489
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and thermal and mechanical properties of (FeCoNiCuCr)(100-x)-Nb-x multiprincipal-element alloys have been investigated in the as-cast and heat-treated state. The alloys were smelted by arc-melting in argon atmosphere. As-cast samples were produced by copper mold casting. The structure was studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. The calculated phase diagrams of the Fe-Co-Ni-Cu-Cr-Nb system were used to predict the phase composition. The predicted thermodynamic temperatures and phase areas were compared with those obtained using differential scanning calorimetry (DSC) and the results of SEM observation, respectively. Addition of 10 at.% Nb caused phase separation of the alloy in the liquid state. Addition of Nb caused an increase in the yield strength by solid-solution hardening and by the formation of intermetallic compounds. Heat treatment also affected the mechanical properties of the studied alloys.
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| 3. |
- Jayakumar, O. D., et al.
(författare)
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Structural and magnetic properties of (In1-xFex)(2)O-3 (0.0 <= x <= 0.25) system : Prepared by gel combustion method
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:5
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Tidskriftsartikel (refereegranskat)abstract
- (In1-xFex)(2)O-3 polycrystalline samples with x=(0.0,0.05,0.10,0.15,0.20, and 0.25) have been synthesized by a gel combustion method. Reitveld refinement analysis of x-ray diffraction data indicated the formation of single phase cubic bixbyite structure without any parasitic phases. This observation is further confirmed by high resolution transmission electron microscopy imaging, indexing of the selected-area electron diffraction patterns, x-ray absorption spectroscopy, and Raman Spectroscopy. dc magnetization studies as a function of temperature and field indicate that they are ferromagnetic with Curie temperature (T-C) well above room temperature.
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| 4. |
- Fazakas, E., et al.
(författare)
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Experimental and theoretical study of Ti20Zr20Hf20Nb20X20 (X = V or Cr) refractory high-entropy alloys
- 2014
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 47, s. 131-138
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the microstructure and mechanical properties of Ti20Zr20Hf20Nb20X20 (X = V or Cr) high-entropy alloys (HEA), produced by induction melting and casting in inert atmosphere. The structures of these alloys were studied via X-ray diffractometry and scanning electron microscopy. Results show that Ti20Zr20Hf20Nb20X20 has mainly the body centered cubic (BCC) structure, whereas the BCC matrix of Ti20Zr20Hf20Nb20X20 contains small amount of Cr2Nb and Cr2Hf intermetallic compounds. Ti20Zr20Hf20Nb20X20 alloy shows the high strength and the homogeneous deformation under compression at room temperature. The strength and hardness of Ti20Zr20Hf20Nb20X20 alloy are further enhanced by the Cr-containing Laves phases segregated during casting. The structural and mechanical properties remained almost unchanged after a short time (10 min) heat treatment at 573, 773, 973 and 1173 K indicating the resistance to working temperature peaks for these two alloys. Ab initio calculations predict ductile behavior for these and similar refractory HEM. The theoretically calculated Young's modulus E is in good agreement with the experimental ones.
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| 5. |
- Louzguine-Luzgin, D.V., et al.
(författare)
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Phase separation process preventing embrittlement of a Zr-Cu-Fe-Al bulk metallic glass.
- 2019
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 167, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- The structural changes and mechanical properties of a Zr 63 Cu 22 Fe 5 Al 10 bulk metallic glass (BMG), and a Zr 63 Cu 27 Al 10 one made for comparison, were studied on annealing below the crystallization temperature. The phase composition of the samples was studied by conventional X-ray diffractometry and high-resolution transmission electron microscopy including the atomic-scale elemental mapping. The samples were mechanically tested in compression. The Zr 63 Cu 22 Fe 5 Al 10 bulk metallic glass shows a high strength and good deformability at room temperature both in the as-cast state and after prolonged structural relaxation below the crystallization temperature. The reasons for such behavior are discussed in the present work.
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| 6. |
- Brennhaugen, David D. E., et al.
(författare)
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Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach
- 2017
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 707, s. 120-125
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Tidskriftsartikel (refereegranskat)abstract
- Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model.
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| 7. |
- Zhao, G-H, et al.
(författare)
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Alloy design by tailoring phase stability in commercial Ti alloys
- 2021
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 815
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical characteristics and the operative deformation mechanisms of a metallic alloy can be optimised by explicitly controlling phase stability. Here an integrated thermoelastic and pseudoelastic model is presented to evaluate the beta stability in Ti alloys. The energy landscape of beta ->alpha ' /alpha '' martensitic transformation was expressed in terms of the dilatational and transformational strain energy, the Gibbs free energy change, the external mechanical work as well as the internal frictional resistance. To test the model, new alloys were developed by tailoring two base alloys, Ti-6Al-4V and Ti-6Al-7Nb, with the addition of beta-stabilising element Mo. The alloys exhibited versatile mechanical behaviours with enhanced plasticity. Martensitic nucleation and growth was fundamentally dominated by the competition between elastic strain energy and chemical driving force, where the latter term tends to lower the transformational energy barrier. The model incorporates thermodynamics and micromechanics to quantitatively investigate the threshold energy for operating transformation-induced plasticity and further guides alloy design.
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