查看更多>>摘要：? 2021 Acta Materialia Inc.Establishing links between the processing, the microstructure and the properties of steel is of utmost importance for rational material design. Including information from the microstructure proves difficult as it requires quantifying the visual information included in microscopy images. The increasing performance of deep learning models in computer vision offers great potential in this regard. Herein, we investigate how features from deep learning models can help us to predict information about the hardness and the composition based on SEM images for a set of complex martensitic steels.
查看更多>>摘要：? 2021Using synchrotron X-ray total scattering and empirical potential structure refinement modelling, we studied systematically in operando condition the disorder-to-order local atomic structure transition in a pure Al and a dilute Al-0.4Sc alloy melt in the temperature range from 690 °C to 657 °C. In the liquid state, icosahedral short-range ordered Sc-centred Al polyhedrons form and most of them with Al coordination number of 10–12. As the melt is cooled to the semisolid state, the most Sc-centred polyhedrons become more connected atom clusters via vertex, edge and face-sharing. These polyhedrons exhibit partially icosahedral and partially face-centred-cubic symmetry. The medium-range ordered Sc-centred clusters with face-sharing are proved to be the “precursors” of the L12 Al3Sc primary phases in the liquid-solid coexisting state.
查看更多>>摘要：? 2021Of transition metals, β-W exhibits the maximum charge-to-spin conversion efficiency. However, due to the lack of phase stability, the β-W-based alloy has rarely been investigated as a spin current generating layer. This study examines W–V alloy layers with various W100-xVx/CoFeB/MgO/Ta heterostructure compositions. X-ray diffraction confirms that the β-W matrix is conserved up to a V content of 20 at%. We attain a maximum damping-like torque efficiency of ?0.45 ± 0.04 for the W80V20 alloy-based heterostructure through the harmonic response method. Furthermore, we determine the spin diffusion length of the W80V20 layer and specify the interfacial spin transparency of the W80V20/CoFeB structure by adopting the spin diffusion model. Consequently, we suggest an intrinsic spin-Hall angle of ?0.86. In addition, we observe in-plane current-induced switching. Our results establish the potential of the β-phase W-V alloy layer as a spin current source layer in spintronic devices.
查看更多>>摘要：? 2021 Acta Materialia Inc.Laser impact welding (LIW) is a promising technique for thin film dissimilar materials solid state welding. The in-situ observation of this process is difficult due to its extreme short timeframe (～1 μs) and high pressure (several GPa). This study revealed the microstructure complexities of the bonding interface at micro/nano-scale for the first time for LIW. Focused ion beam (FIB) and transmission electron microscopy (TEM) showed multiple structures along 5 μm long laser impact welded Al-Ti interface including smooth interface (length of 200 nm), intrusion structure (length of 800 nm), nanocrystal structure (diameter of 180 nm), diffusion structure (diffusion distance of 2 μm), and porous structure (pore size of 1–50 nm). The variety of the micro/nano scale microstructures reflected the uneven vertical impact pressure and horizontal frictional force. The findings revealed the multiplicity of the bonding mechanisms for LIW along the interface and help to precisely control the welding process.
查看更多>>摘要：? 2021 The Author(s)Recent synchrotron X-ray measurements examined three-dimensional boundary migration during recrystallization [Scripta Mater 205 (2021) 114187]. To analyze possible correlations between grain boundary mobility and the observed heterogeneous boundary migration, molecular dynamics simulations were carried out. Migration of two selected boundary segments were simulated in both planar and spherical bicrystal atomistic models. These two segments were chosen because in the experiment one was observed to migrate much faster than the other. The simulations reveal that mobility cannot account for the experimentally observed heterogeneous migration. The result points to the possibility that recrystallization boundary migration strongly depends on features within the deformed microstructure.
查看更多>>摘要：? 2021Printing gold alloys parts is a challenge due to the high reflectivity and thermal conductivity of these materials. Recent studies show an improvement in printing gold using the Laser Powder Bed Fusion (L-PBF) process; however, the impact of the A1→L10 phase transformation on printed red-gold alloy has not been studied. In this work, 3D printed red-gold samples with different post-processing conditions have been heat-treated at 250 °C to investigate the effect of the sample stress states on variant selection, by Electron Backscatter Diffraction. Synchrotron X-ray diffraction experiments reveal the presence of a non-negligible amount of tetragonal phase in the as-build red-gold samples. The use of an intermediate heat treatment at 600 °C to eliminate small domains of tetragonal phase formed during the manufacturing process demonstrates that the crystallographic textures following heat treatment are highly dependent on the stress-state during the early stage of the phase transformation.
查看更多>>摘要：? 2021 Acta Materialia Inc.The authors regret there was an error in the author and affiliations list of this article. The correct author list and affiliations are now shown above. The authors would also like to make an addition to the Acknowledgments of this article which reads as follows: Portions of this research were conducted with high-performance computational resources provided by Louisiana State University (http://www.hpc.lsu.edu) and the Louisiana Optical Network Infrastructure (http://www.loni.org). The authors would like to apologise for any inconvenience caused.
查看更多>>摘要：? 2021 The Author(s)Owing to their combination of high hardness and increased fracture toughness, CrTaN coatings have recently gained increasing interest as suitable candidates for metal cutting applications. However, up to now, the detailed mechanisms underlying the oxidation of this promising coating system are not thoroughly understood. Thus within this work, the evolution of microstructure and phase composition of a cathodic arc evaporated Cr0.74Ta0.26N coating were illuminated in ambient atmosphere up to 1400 °C. In situ high-energy X-ray diffraction showed that powdered face-centered cubic (fcc) CrTaN displays an excellent oxidation resistance up to ～1050 °C, where the formation of tetragonal (t) CrTaO4 and rhombohedral (r) Cr2O3 sets in. The compact CrTaN deposited on sapphire subjected to 1225 °C in ambient atmosphere exhibits intact fcc-CrTaN regions near the substrate, a porous intermediate layer of r-Cr2O3 and t-CrTaO4 and a dense r-Cr2O3 oxide scale at the surface.
查看更多>>摘要：? 2022 Acta Materialia Inc.Intrinsic friction and corrosion issues of light alloys impede their application in tribological and corrosive environments, thus a proper ceramic coating is normally required to overcome these issues for practical engineering deployment. Here, we developed a new approach to fabricate controllable and self-lubricating nanocomposite coating by combining in-situ synthesis of MoS2 and plasma electrolytic oxidation (PEO) process. It is found that the coefficient of friction of this new coating is only about a quarter of the coatings obtained by traditional PEO process due to the self-lubricating characteristic of gradient MoS2. More importantly, this ceramic coating exhibits excellent interfacial strengthen through edge-pinning by noncoherent, which endows excellent tribological and adhesive properties. This facile technique provides a new strategy to fabricate self-lubricating ceramic coating for light alloys, and is believed to have great potential applications in wide engineering sectors and open new avenues for designing novel alloy systems for extreme conditions.
查看更多>>摘要：? 2021 Acta Materialia Inc.The application of Al-Mg-Si alloys is growing in fracture critical applications such as transportation. The formation of grain boundary precipitates during cooling after solution treatment is an important factor in controlling low energy intergranular fracture modes. A systematic study was conducted on the effects of grain boundary misorientation and cooling rate (between 3 and 1000 °C/s) on the size and density of grain boundary precipitates before and after artificial ageing. It was found that precipitates on high angle grain boundaries were ≈3 times larger than those formed on low angle boundaries. The grain boundary precipitate size decreased by a factor of 3 when the cooling rate increased from 3 to 80 °C/s with no precipitates observed at 1000 °C/s. However, even for a cooling rate of 1000 °C/s, grain boundary precipitation was observed during subsequent artificial ageing. The effects of grain boundary misorientation and cooling rate were rationalized by enhanced diffusion at grain boundaries.
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