Pore/skeleton structure and compressive strength of porous Mo3Si-Mo5Si3-Mo5SiB2 intermetallic compounds prepared by spark plasma sintering and homogenization treatment

Highlights: • Porous Mo₃Si-Mo₅Si₃-Mo₅SiB₂ intermetallics were fabricated by SPS and HT. • Mo₃Si-Mo₅Si₃-Mo₅SiB₂ did not exhibit plastic deformation at room temperature. • Transgranular cleavage fracture dominated the crack propagation in the skeletons. • At constant porosity, strength can be increased by increase in the J value via HT. -- Abstract: Next to aluminum-based porous alloys, porous Mo-Si-B intermetallic compounds are the most promising filtration and separation material to handle harsh service conditions of ultra-high-temperature corrosive environment. Porous Mo₃Si-Mo₅Si₃-Mo₅SiB₂ intermetallics were fabricated by a two-step method of spark plasma sintering (SPS) and homogenization treatment (HT) using Mo, Si, and B as the starting powders. In addition, the evolution of the pore/skeleton structure and compressive behavior of porous Mo₃Si-Mo₅Si₃-Mo₅SiB₂ intermetallic compounds by the two-step method was investigated. In SPS, the phase transformation included a solid–liquid reaction and solid–solid diffusion, and the pore structure changed significantly with the increase of sintering temperature. By HT, smooth skeletons and size centralized pores were obtained. With the increase in the HT time, the precise control of pore/skeleton structure parameters was achieved while simultaneously maintaining stable porosity. Combined SPS+HT led to a wide range of porosities, and pore/skeleton parameters were controlled by the sintering temperature and SPS pressure. Compression test results indicate that the porous Mo₃Si-Mo₅Si₃-Mo₅SiB₂ intermetallics do not exhibit a plastic deformation ability at room temperature and that the transgranular cleavage fracture dominates the crack propagation in the skeletons. The quantitative relationship between porosity and compressive strength was established by σ_c = σ_c0 × (1 – ρ)^1/J. The effect of HT on the pore structure factor J was revealed: at constant porosity, the strength can be increased by the increase in the J value via HT.