| 31. |
- Ryttberg, Kristina, 1977, et al.
(författare)
-
The effect of cold ring rolling on the evolution of microstructure and texture in 100Cr6 steel
- 2010
-
Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 527:9, s. 2431-2436
-
Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the development of microstructure and texture during cold ring rolling of 100Cr6 steel rings with starting rectangular cross-sections. By interrupting the rolling process at pre-defined intervals expansion ratios ranging from 1.05 to 1.5 were achieved resulting in varying degrees of deformation of the rings. Results for rings with a simple rectangular cross-section were compared with results for a cold rolled ring with a more complex cross-section. By combining results from optical and scanning electron microscopy with hardness measurements the two different ring shapes were shown to display similar material flow during cold ring rolling. The deformation was most severe near the inner diameterof the rings decreasing towards the area of the outer diameter. By employing electron back scatter diffraction (EBSD) the ring rolling process was shown to change the {111}-fibre texture of the ring blanks to a {110} texture. This implies a mixture of both shear and compressive deformation during rolling.
|
|
| 32. |
|
|
| 33. |
- Tam, Eric, 1980, et al.
(författare)
-
XRD and XPS Characterisation of Transition Metal Silicide Thin Films
- 2012
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 606:3-4, s. 329-336
-
Tidskriftsartikel (refereegranskat)abstract
- Binary transition metal silicides based on the systems Ti-Si, Fe-Si, Ni-Si and Cr-Si were fabricated on Si wafers by means of ion-beam co-sputter deposition and subsequent annealing. The crystalline structures of the phases formed were identified from the characteristic patterns acquired by means of X-ray diffraction (XRD) measurements. The phase formation sequences were described by means of the Pretorius’ effective heat of formation (EHF) model. For the Ti-Si, Fe-Si and Ni-Si systems, single phase thin films of TiSi2, β-FeSi2 and NiSi2 were generated as the model predicts, while a mixture of CrSi + CrSi2 phases was obtained for the Cr-Si system. The surface chemical condition of individual specimens were analysed by using X-ray photoelectron spectroscopy (XPS). The chemical shifts of transition metal 2p3/2 peaks from their metallic to silicide states were depicted by means of the Auger parameters and the Wagner plots. The positive chemical shift of 2.0 eV for Ni 2p3/2 peak of NiSi2 is mainly governed by the initial-state effects. For the other silicide specimens, the initial-state and final-state effects may oppose one another with similar impact. Consequently, smaller binding energy shifts of both negative and positive character are noted; a positive binding energy shift of 0.3 eV for the Fe 2p3/2 level was shown for β-FeSi2 and negative binding energy shifts of 0.1 and 0.3 eV were determined for CrSi + CrSi2 and TiSi2, respectively.
|
|
| 34. |
- Townsend, Philip, 1991, et al.
(författare)
-
Tessellation-based stochastic modelling of 3D coating structures imaged with FIB-SEM tomography
- 2021
-
Ingår i: Computational Materials Science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 197
-
Tidskriftsartikel (refereegranskat)abstract
- To facilitate printing, coatings are typically applied to paperboard used for packaging to provide a good surface for application. To optimise the performance of the coating, it is important to understand the relationship between the microstructure of the material and its mass transport properties. In this work, three samples of paperboard coating are imaged using combined focused ion beam and scanning electron microscope (FIB-SEM) tomography data appropriately segmented to characterise the internal microstructure. These images are used to inform a parametric, tessellation-based stochastic three-dimensional model intended to mimic the irregular geometry of the particles that can be seen in the coating. Parameters for the model are estimated from the FIBSEM image data, and we demonstrate good agreement between the real and virtual structures both in terms of geometrical measures and mass transport properties. The development of this model facilitates exploration of the relationship between the structure and its properties.
|
|
| 35. |
- Krakhmalev, Pavel, 1973-, et al.
(författare)
-
Microstructure, solidification texture, and thermal stability of 316 L stainless steel manufactured by laser powder bed fusion
- 2018
-
Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 8:8, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.
|
|
| 36. |
- Saarimäki, Jonas, et al.
(författare)
-
3D Residual Stresses in Selective Laser Melted Hastelloy X
- 2017
-
Ingår i: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016). - : Materials Research Forum LLC. ; , s. 73-78
-
Konferensbidrag (refereegranskat)abstract
- 3D residual stresses in as manufactured EOS NickelAlloy HX, produced by laser powder bed additive manufacturing, are analysed on the surface closest to the build-plate. Due to the severe thermal gradient produced during the melting and solidification process, profound amounts of thermal strains are generated. Which can result in unwanted geometrical distortion and effect the mechanical properties of the manufactured component. Measurements were performed using a four-circle goniometer Seifert X-ray machine, equipped with a linear sensitive detector and a Cr-tube. Evaluation of the residual stresses was conducted using sin2ψ method of the Ni {220} diffraction peak, together with material removal technique to obtain in-depth profiles. An analysis of the material is reported. The analysis reveals unwanted residual stresses, and a complicated non-uniform grain structure containing large grains with multiple low angle grain boundaries together with nano-sized grains. Grains are to a large extent, not equiaxed, but rather elongated.
|
|
| 37. |
- Gaska, Karolina, 1986, et al.
(författare)
-
Gas Barrier, Thermal, Mechanical and Rheological Properties of Highly Aligned Graphene-LDPE Nanocomposites
- 2017
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:7, s. 294-
-
Tidskriftsartikel (refereegranskat)abstract
- This contribution reports on properties of low-density polyethylene-based composites filled with different amounts of graphene nanoplatelets. The studied samples were prepared in the form of films by means of the precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement of graphene flakes and results in a strong anisotropy of composites morphology. The performed tests of gas permeability reveal a drastic decrease of this property with increasing filler content. A clear correlation is found between permeability and free volume fraction in the material, the latter evaluated by means of positron annihilation spectroscopy. A strong anisotropy of the thermal conductivity is also achieved and the thermal conductivity along the extrusion direction for samples filled with 7.5 wt % of GnP (graphene nanoplatelets) reached 2.2 W/m·K. At the same time, when measured through a plane, a slight decrease of thermal conductivity is found. The use of GnP filler leads also to improvements of mechanical properties. The increase of Young’s modulus and tensile strength are reached as the composites become more brittle.
|
|
| 38. |
- Shaikh, Abdul Shaafi, 1989, et al.
(författare)
-
On the effect of building platform material on laser-powder bed fusion of a Ni-base superalloy HAYNES® 282®
- 2023
-
Ingår i: European Journal of Materials. - : Informa UK Limited. - 2688-9277. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) by laser powder bed fusion (LPBF) involves melting of layers of powder onto a substrate, called a building platform. Due to cost or convenience considerations, building platform materials rarely match the LPBF material, especially for high temperature materials. To ensure tolerances in component geometries, AM components are often stress-relieved/heat-treated while still attached to the building platform. It is therefore important to understand the effect of dissimilar building platform materials on the properties of the built-up material. These effects may be particularly important for high performance materials such as Ni-base superalloys used for critical applications in the aerospace and energy industries. To investigate this effect, samples of a Ni-base superalloy HAYNES® 282® were built onto a carbon steel building platform in several configurations. The samples were removed from the building platform after heat treatment and subjected to detailed composition analysis and microstructural characterization to investigate the effect of the building platform material on the properties of the additively manufactured part. Room temperature and high temperature tensile testing were used to characterize the material. Results showed no risk of large-scale chemical composition change, or mechanical property degradation of built-up material from on-platform heat treatment.
|
|
| 39. |
- Bojestig, Eric, 1991, et al.
(författare)
-
Laser powder bed fusion of bronze - Process optimization and influence on microstructure and mechanical properties
- 2019
-
Ingår i: Euro PM 2019 Congress and Exhibition.
-
Konferensbidrag (refereegranskat)abstract
- As the interest in additive manufacturing increases, so does the demand for new materials. Among these are the copper alloys due to their good bearing properties, corrosion resistance and electrical conductivity. When attempting to print Cu-base materials with laser powder bed fusion, their low laser absorption and high thermal conductivity restricts the attainable local heat absorption in the material and hence the manufacturability with respect full density processing, especially for pure Cu. Alloyed Cu constitutes, however, less challenge in this respect. Hence, spherical gas atomized bronze (Cu-11Sn) powder was used and all printing was performed in an EOS M100 machine in argon atmosphere. Design of experiment method was used to determine optimized process parameters with respect to laser power, scan speed and hatch distance. Full density (99.9%) parts were successfully fabricated with UTS>400 MPa and the fine cellular microstructure was displayed. Furthermore, thin wall capacity of 150 µm was demonstrated.
|
|
| 40. |
- Wang, Shuping, 1987, et al.
(författare)
-
Temperature evolution during the compaction of calcium silicate hydrate powders using a compression calorimeter
- 2020
-
Ingår i: Journal of Thermal Analysis and Calorimetry. - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 139:2, s. 863-875
-
Tidskriftsartikel (refereegranskat)abstract
- Amorphous calcium silicate hydrate (CSH) undergoes contact-hardening property, i.e. the powder can be hardened by compression. A compression calorimeter was designed to determine the temperature evolution during the compaction of the powder. A platinum sensor (Pt100) was used as the temperature sensor and was positioned in the powder as well as in the compression die. A resolution of 0.01 °C with a sampling time of every second was used to monitor the temperature. Both theoretical calculation and simulations by COMSOL multiphysics showed that the device reliably evaluated the temperature during the compaction of CSH powders. The measurement was taken under semi-adiabatic conditions. The temperature profiles obtained from the measurement revealed the compression process and bonding development during the compaction of the powders. Finally, a linear relationship was observed between the compressive strength and the maximum temperature increase. This provides insight into the contact-hardening mechanism during the compaction of CSH powders.
|
|
