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Additive manufacturing (AM) techniques including laser powder bed fusion have been widely used to produce metallic components with microstructures and mechanical properties distinctly different from the conventionally manufactured counterparts. Understanding how AM parameters affect the evolution of microstructure, including texture, of these AM metallic components is critical for appropriate manipulation of their processing and therefore their mechanical properties. Here we conducted a systematic investigation of texture evolution of a face-centred cubic CrMnFeCoNi high-entropy alloy cuboid fabricated using laser powder bed fusion. Our results showed that the texture evolutions along the build direction were different between the corner and central parts of the sample. Detailed analysis suggested that the texture evolution is closely related to local thermal gradient, which is a property that can be manipulated through changing AM parameters. The different textures lead to the significant variations of mechanical properties within the sample. [ABSTRACT FROM AUTHOR]

Hot deformation behaviour of 40Cr was investigated by conducting hot compression tests at the temperature range of 750–1050°C and the strain rate range of 0·01–10 s−1 on a Gleeble 1500 thermal mechanics simulator. Most true stress–strain curves show that the flow stress increases until a peak value and then decreases with the increasing of the strain, which ends up with a stationary stage. Further microstructural observation confirms the occurrence of dynamic recrystallisation behaviour of 40Cr. The experimental data were used to develop a constitutive equation on the basis of the Arrhenius equation. In the constitutive equation, the effect of strain on deformation behaviour is incorporated, and the flow stress correction parameters p1, p2, p3, p4 and p5 are represented by the Zener–Holloman parameter. The flow stresses predicted by the constitutive equation show good agreement with the experimental stresses, with the mean error <4·86%. [ABSTRACT FROM AUTHOR]

Effects of activating fluxes on macromorphologies, microstructures and mechanical properties of low power pulse laser beam welding of AZ31 magnesium alloy joints were investigated by microstructural observations and mechanical properties tests (including the ultimate tensile strength and hardness). The results showed that activating flux (SiO2) is more effective in improving the laser welded penetrations when the heat input is at a critical value (E = 53·42 J mm-1). Five typical fluxes (SiO2, TiO2, ZnCl2, CaCl2 and CaF2) all increased the weld penetrations and D/W ratios of the welded joints. The morphologies of grains in the band zones with fluxes are characterised by dendritic crystals. Moreover, the widths of the band zones with oxide and chloride fluxes are wider than that with fluorine flux. The mechanical properties of the welded joints with fluxes were lower than those without flux. The fracture surface of the welded joints with fluxes exhibited a character of a mixed fracture. [ABSTRACT FROM AUTHOR]

The effects of mix activated fluxes on the penetrations, microstructures and mechanical properties of tungsten inert gas (TIG) welded AZ31 magnesium alloy joints were studied. The results showed that an increase in the amount of TiO2 coating improved the weld penetration and depth/width ratio of the TIG welded AZ31 magnesium alloy seams. The α-Mg grains of the fusion zone (FZ) became fine gradually with the addition of CaF2 coating but coarsened sharply when the amount of TiO2 coating was over 70%. In addition, the porosities and total length of solidification cracks in the FZ were reduced by the CaF2 and TiO2 coatings. The ultimate tensile strength value of the welded joints increased with the addition of TiO2 coating but decreased sharply when more TiO2 coating was adopted. [ABSTRACT FROM AUTHOR]