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The Inconel 718 superalloy demonstrates the potential to fabricate high-temperature components using additive manufacturing. However, additively manufactured Inconel 718 typically exhibits low strength, necessitating post-heat treatments for precipitate strengthening. This study investigated the microstructures and mechanical properties of the Inconel 718 superalloy fabricated via laser powder bed fusion. The room-temperature and high-temperature tensile properties of the Inconel 718 alloy samples following various post-heat treatments were evaluated. The results indicate that the as-built samples exhibited columnar grains with fine cell structures. Solution treatment resulted in δ phase formation and grain recrystallization. Subsequent double aging led to finely distributed nanoscale γ′ and γ″ particles. These nanoscale particles provided high strength at both room and high temperatures, resulting in a balanced strength and ductility comparable to the wrought counterpart. High-temperature nanoindentation analyses revealed that the double-aging samples exhibited very high hardness and low creep rates at 650 °C. [ABSTRACT FROM AUTHOR]

Titanium parts fabricated by additive manufacturing, i.e., laser or electron beam-powder bed fusion (L- or EB-PBF), usually exhibit columnar grain structures along the build direction, resulting in both microstructural and mechanical anisotropy. Post-heat treatments are usually used to reduce or eliminate such anisotropy. In this work, Ti-6Al-2Zr-1Mo-1V (TA15) alloy samples were fabricated by L-PBF to investigate the effect of post-heat treatment and load direction on the dynamic response of the samples. Post-heat treatments included single-step annealing at 800 °C (HT) and a hot isotropic press (HIP). The as-built and heat-treated samples were dynamically compressed using a split Hopkinson pressure bar at a strain rate of 3000 s−1 along the horizontal and vertical directions paralleled to the load direction. The microstructural observation revealed that the as-built TA15 sample exhibited columnar grains with fine martensite inside. The HT sample exhibited a fine lamellar structure, whereas the HIP sample exhibited a coarse lamellar structure. The dynamic compression results showed that post-heat treatment at 800 °C led to reduced flow stress but enhanced uniform plastic strain and damage absorption work. However, the HIP samples exhibited both higher stress, uniform plastic strain, and damage absorption work owing to the microstructure coarsening. Additionally, the load direction had a subtle influence on the flow stress, indicating the negligible anisotropy of flow stress in the samples. However, there was more significant anisotropy of the uniform plastic strain and damage absorption. The samples had a higher load-bearing capacity when dynamically compressed perpendicular to the build direction. [ABSTRACT FROM AUTHOR]

Taking the reclamation waste dump of the open-pit mining area in the east of Inner Mongolia Steppe as our study area, we sampled field investigation and laboratory measurements to study the changes of soil physical and chemical properties in the waste dump of the open-pit mining area during its recovery years. The objective of this study was aiming to provide theoretical support for the ecosystem restoration and reconstruction in the open-pit mining area of grasslands in the Northwest of China. The results showed that: 1) the mechanical composition of soil all layers in different reclamation years was mainly composed of silt, except for 20-30cm; the silt content was significantly higher than the control area (CK), and the silt content of surface soil (0-5cm) in reclamation 3 years (2016) was significantly higher than CK, but the sand content was significantly lower than CK; 2) In the early stage of vegetation restoration and succession, the physical and chemical properties of soil in different reclamation years were significantly different. With the increase of reclamation years, TOC and TN content decreased, but TP content did not change significantly during reclamation years. Based on the above results, the change characteristics of soil physical and chemical properties in the early stage of vegetation restoration succession were discussed. The research results have certain theoretical significance and practical guidance value for the ecological restoration and reconstruction of open-pit mining areas in the north of Northwest China.