Aluminum alloy capsules play a critical role in shape control, heat transfer, and pressure transmission during the PM-HIP sintering of Al-based powders. As the weakest part of the capsule, the reliability of the welded joint is crucial for the safe operation of the HIP process and the quality of the final product. This study investigated the effects of two typical HIP temperatures on the evolution of second phases and texture. The results show that: (1) At 400 °C, suppressed Si diffusion retains a continuous, low-melting-point Al-Si eutectic network and needle-like secondary phases in the weld zone, thereby impeding residual stress relief. Compositional segregation in the heat-affected zone weakens grain boundary stability. The texture undergoes only limited recovery, with a strong orientation retained and micro-strain not effectively relieved, restricting joint ductility. (2) At 510 °C, Si is sufficiently spheroidized, forming a bead-like structure. Needle-like second phases transform into globular/short-rod morphologies, disrupting the continuity of the brittle phases. Simultaneously, complete recrystallization is induced, resulting in a randomized texture and significant release of micro-strain, thereby improving microstructural homogeneity and plastic deformation capacity. This study suggests that the internal stress concentration arising from the low-melting-point eutectic phase and strong texture poses a failure risk for the capsule. Therefore, employing the 510 °C HIP process to achieve second-phase spheroidization and texture weakening can significantly mitigate this failure risk.

Ni–Mo alloy claddings were fabricated on low-carbon steel substrates using powder metallurgy combined with hot isostatic pressing (PM-HIP). The interfacial microstructure, elemental interdiffusion, phase composition and microhardness distribution of the bimetallic composite were investigated systematically. The results show that sound metallurgical bonding without pores, cracks and element dilution is achieved under the HIP process of 1100 °C, 120 MPa and 4 h holding time. Interdiffusion of Fe, Ni and Mo atoms forms a 20–50 μm thick interfacial transition layer, and Mo exhibits a relatively low diffusion capacity due to its large atomic radius. Two intermetallic phases, Ni₄Mo and NiMo, are formed in the cladding layer because of the inhomogeneous distribution of Mo. A prominent microhardness gradient is observed throughout the composite, and the interfacial layer presents the highest hardness of 905 HV resulting from multiple strengthening mechanisms. As an effective alternative to traditional welding and cladding technologies, the PM-HIP process exhibits great potential for manufacturing complex bimetallic components with prospective service prospects in severe corrosive environments.

The corrosion behavior of high-entropy alloys under cyclic wet–dry conditions simulating the salt-lake atmosphere was investigated. The composition, morphology, and electrochemical properties of the corrosion products formed on the alloy surface after corrosion were systematically analyzed. The results show that in a chloride-containing environment with alternating temperature and humidity, the Cr-containing oxide passive film formed on the alloy surface effectively inhibits the corrosion process in the early stages. In addition, electrochemical results show that the charge transfer resistance in the MgCl₂ system reaches 4.96 × 10⁵ Ω·cm² at prolonged exposure, which is significantly higher than that in the NaCl system, indicating a lower corrosion rate. However, over time, the passive film undergoes localized rupture due to chloride ion attack and stress, leading to pitting corrosion and expansion toward the substrate. This study reveals the corrosion mechanism of high-entropy alloys in high-altitude salt-lake atmospheric environments and provides crucial insights for material design and performance optimization for their engineering applications in salt-lake scenarios.