Effect of Sintering Temperatures on Grain Coarsening Behaviors and Mechanical Properties of W-NiTi Heavy Tungsten Alloys

• Published in: Materials Vol. 15; no. 22; p. 8035
• Main Authors: Shao, Yang, Yu, Weikang, Wu, Jifei, Ma, Haiwen
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 14.11.2022; MDPI
• Subjects: Acids; Activation energy; Alloys; Atoms & subatomic particles; Behavior; Coarsening; Compression tests; Diffraction; Grain growth; Hot pressing; Intermetallic compounds; Investigations; Iron compounds; Mechanical properties; Nickel base alloys; Nickel compounds; Nickel titanides; NiTi binder; Particle size; Plasma sintering; Powders; Shape memory alloys; Sintering; Sintering (powder metallurgy); Temperature; Tungsten; Tungsten alloys; Tungsten base alloys; tungsten heavy alloys; X-rays; Yield stress; activation energy; NiTi binder; tungsten heavy alloys
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma15228035

W-NiTi tungsten heavy alloys were prepared by an infiltration process using submicron W powders, and the effect of sintering temperatures on grain-coarsening behaviors and the mechanical properties of W-NiTi tungsten heavy alloys were investigated. The microstructures and mechanical properties were investigated using scanning electron microscopy, X-ray diffraction and compression tests. The results showed that tungsten particles were uniformly distributed in the NiTi binder. The W-NiTi tungsten heavy alloys consisted of B19'-NiTi and body-centered cubic W phases. The average tungsten particle sizes of W-NiTi tungsten heavy alloys sintered at 1400 °C, 1480 °C and 1560 °C were 2.62 μm, 4.04 μm and 5.20 μm, respectively. The average tungsten particle size increased with sintering temperatures, while the densities decreased at higher temperatures. The cavities retained in the W-NiTi tungsten heavy alloy sintered at 1560 °C, which degraded the mechanical properties. The calculated grain growth activation energy of W particles in the NiTi binder was 330 kJ/mol, which was higher than those in conventional W-NiFe and W-NiCo tungsten heavy alloys. The higher activation energy means more difficult diffusion process of W atoms in NiTi binders during sintering. Therefore, finer-grained heavy tungsten alloys were more easily obtained by using NiTi binders. Yield strength of W-NiTi tungsten heavy alloys decreased with increasing sintering temperatures due to coarsened tungsten particles.