The efficiency of the fabrication and the cost of feedstock materials are important constraining factors for a wider application of the laser powder bed fusion (LPBF) process in the industry. Therefore, it is necessary to investigate the feasibility of using different particle size distributions (PSD) combined with higher layer thickness for achieving higher building efficiency and cost-effectiveness. This paper focuses on the effect of PSD (0–53, 15–53, 15–75, and 15–105 μm) on the print quality and mechanical properties of the LPBF-processed Ti-6Al-4V at a layer thickness of 60 μm. The results show that volumetric energy density (VED) range, which allows the coarse powder to reach full density, becomes relatively narrower but is still capable of producing fully dense parts when the parameters are properly adjusted. Among the fully dense specimens, the surface roughness varies slightly with the increase of VED and PSD. In the case of proper parameter selection, specimens made of coarse powder can still achieve low surface roughness. Only slight differences in mechanical performance are found for specimens produced using different PSD powders as they have almost identical microstructures. The issue of the anisotropic mechanical properties of the as-built specimens is resolved after annealing treatment at 800 °C for 2 h. This study provides a guideline for producing high-quality Ti-6Al-4V parts using a higher layer thickness and coarser powders.

Gas-induced porosity is almost inevitable in additively manufactured aluminum alloys due to the evaporation of low-melting point elements (e.g., Al, Mg, and Zn) and the encapsulation of gases (e.g., hydrogen) during the multiple-phase reaction in the melt pool. These micropores are highly unstable during post-heat treatment at elevated temperatures and greatly affect mechanical properties and service reliability. In this study, the AlSi10Mg samples prepared by LPBF were subjected to solution heat treatment at 560 °C for 0.5 and 2 h, followed by artificial aging at 160 °C, 180 °C and 200 °C, respectively. The defect tolerance of gas porosity and associated damage mechanisms in the as-built and heat treated AlSi10Mg alloy were elucidated using optical, scanning electron microscopic analysis, X-ray micro computed tomography (XCT) and room temperature tensile testing. The results showed the defect tolerance of AlSi10Mg alloy prepared by LPBF was significantly reduced by the artificial aging treatment due to the precipitation of Mg-Si phases. Fracture analysis showed that the cooperation of fine precipitates and coarsened micropores assists nucleation and propagation of microcracks sites due to stress concentration upon tensile deformation and reduces the tensile elongation at break.

Spatially resolved elastic strains in the bulk interior of a laminated Ti-Al metal composite were studied during in situ tensile loading at strains up to 1.66% by a synchrotron-based micro-diffraction technique, namely differential aperture X-ray microscopy (DAXM). For both Al and Ti grains, deviatoric elastic strains were estimated based on polychromatic X-ray microbeam diffraction, while lattice strains along the normal direction of the tensile sample were directly measured using monochromatic X-ray microbeam diffraction. The estimated deviatoric strains show large spatial variations, and the mean values are consistent with the external loading conditions, i.e., increasing tensile strain along the tensile direction and increasing compressive strain along the sample normal with increasing loading. The directly measured lattice strains also show large spatial variations, although the magnitude of this variation is smaller than that for the estimated deviatoric strain. The directly measured lattice strains in Ti grains are largely consistent with the external loading, whereas those in Al grains are in contradiction with the external loading. The causes of the experimental results are discussed and related to both the laminated microstructure of the composite material and the limitations of the techniques.

Magnesium alloys with a high volume fraction of secondary phases exhibit inferior formability. Therefore, investigating their thermal deformation characteristics is critical for optimizing thermal processing techniques. In this work, isothermal compression experiments were performed on a Mg-15Gd-8Y-6Al-0.3Mn alloy with an elastic modulus of 51.3 GPa with a substantial volume of aluminum-rare earth (Al₂RE) phases. The rheological behavior and microstructural evolution of the material were systematically investigated at varying temperatures (350–500 °C) and strain rates (0.001–1.000 s⁻¹). The calculated thermal processing diagram indicates that the unstable region gradually enlarges with increased strain, and all unstable regions appear within the high-strain-rate, low-temperature domain. The ideal thermal processing range of the alloy is 350–500 °C at strain rates ranging from 0.001 to 0.016 s⁻¹. Particle-stimulated nucleation and discontinuous dynamic recrystallization are both verified to be responsible for the recrystallized microstructure of the alloy. The recrystallized grains exhibit a relatively random crystallographic orientation. As recrystallization proceeds, the texture gradually transitions from a typical [0001] texture in the compression direction to a random texture accompanied by decreased texture intensity. This work sheds new light on the thermo-mechanical processing of high-modulus Mg alloys, which could help design suitable processing techniques for related materials.