This study was conducted for high temperature aging (HTA) to simultaneously reduce current treatment time and increase the tensile ductility of 7075 aluminum alloy. Various high temperatures and different durations for artificial aging were compared. We investigated the microstructure and the tensile properties of 7075 aluminum alloy extruded rod after various HTAs, and compared them with the outcomes of full annealing (O). The total elongation (TE) of the specimen after solution heat treatment (490 °C, 1 h) and artificial aging (280 °C, 12 h) was about 25%. For full annealing, it is known as 21%. The reason for this was the formation of the η phase in the matrix, which had fewer large particles (Al-Cu phase). The hardening of HTA specimens is higher than that of O, indicating necking resistance during homogeneous plastic deformation. Thereby, HTA treatment increases the formability of 7075 aluminum alloy.

Powder metallurgy (PM) has been widely used to produce various steels in industry, mainly due to its capabilities for manufacturing nearly net-shaped products and mass production. To improve the performances of PM stainless steels, the roles of 0.6 wt% B additive in the microstructures, mechanical properties, and corrosion resistances of PM 304L austenitic, 410L ferritic, and 410 martensitic stainless steels were investigated. The results showed that adding 0.6 wt% B significantly improved the sintered densities of the three kinds of stainless steels due to the liquid phase sintering (LPS) phenomenon. The borides in 304L + 0.6B, 410L + 0.6B, and 410 + 0.6B were rich in B and Cr atoms but deficient in Fe, Ni, or C atoms, as analyzed by electron probe micro-analysis. Furthermore, the B additive contributed to the improved apparent hardness and corrosion resistance of PM stainless steels. In the 410L stainless steel, the 0.6 wt% B addition increased the corrosion voltage from −0.43 V_SCE to −0.24 V_SCE and reduced the corrosion current density from 2.27 × 10⁻⁶ A/cm² to 1.93 × 10⁻⁷ A/cm². The effects of several factors, namely: porosity; the generation of boride; the matrix/boride interfacial areas; Cr depletion; and the microstructure on the corrosion performances are discussed. The findings clearly indicate that porosity plays a predominant role in the corrosion resistances of PM austenitic, ferritic, and martensitic stainless steels.

In additive manufacturing (AM) metallic materials, heat treatment (HT) is a common process for modifying the unstable and anisotropic microstructure. Selective laser melting (SLM) Corrax maraging stainless steel is a novel material that has been applied in mold materials with conformal cooling channels in industry. However, the influences of HTs on the various mechanical properties of SLM Corrax steels are still not fully clarified. The aim of this research was thus to clarify the effects of solution treatment (S) and integrated solution-aging treatment (SA) on the hardness and impact toughness of SLM Corrax maraging stainless steel. Furthermore, to identify the roles of building direction (BD) on the hardness and impact toughness, parallelly built (P) and vertically built (V) SLM Corrax steels were fabricated and compared. The microstructures were examined by X-ray diffraction, electron backscatter diffraction, and electron probe micro-analysis, and to observe the fracture surface, scanning electron microscopy was used. The results showed that both the impact energies and apparent hardnesses were dominated by the HT. S treatment simultaneously decreased the impact energies and apparent hardnesses. SA treatment increased the apparent hardnesses but decreased the impact energies. BD did not apparently affect either the hardness or the toughness. Furthermore, the percentage of austenite did not affect the impact energies of the various material conditions. In the SA condition, the apparent hardnesses of P and V specimens were 49.9 HRC and 49.3 HRC, respectively. The impact energies of SA-P and SA-V specimens were 20 J and 17 J, respectively. The low anisotropy of SA specimens in hardness and toughness can be attributed to the weak texture and is advantageous to the material’s stability during service.