采用硬度测试、金相显微镜、X射线衍射、扫描电镜、透射电镜和能谱分析技术, 研究热处理工艺对V₅₅Ti₃₀Ni₁₅合金组织和硬度的影响.不同热处理温度和时间下的合金显微组织对合金硬度有很大影响.研究结果表明:铸态合金由过饱和钒基固溶体以及非平衡的NiTi和NiTi₂相组成.合金在750和800℃热处理时, 细小NiTi粒子从过饱和钒基固溶体中析出,随着保温时间延长, NiTi粒子析出增多.NiTi粒子析出降低了钒基固溶体的晶格畸变度, 合金硬度降低.合金在850和900℃热处理时, NiTi析出粒子逐步回溶到钒基固溶体中,晶格畸变度升高, 合金硬度升高. 在900℃热处理初期,合金硬度下降是由于铸造应力的消除, 晶格畸变度降低.而随后由于NiTi₂相在相界上聚集球化, 使得合金的硬度开始升高.

V₅₅Ti₃₀Ni₁₅ alloy seems to be a promising alloy as a potential replacement for Pd－based alloy, which may reach a good combination of hydrogen permeability and mechanical stability in hydrogen. Metal rolling process is most widely used for sheet fabrication and may make multiphase V－Ti－Ni metallic membranes being thinner for increasing hydrogen transport flux. Different heat treatment processes have been carried out on a selected V₅₅Ti₃₀Ni₁₅ alloy to soften for improved workability in this work. The effect of heat treated process on microstructure and hardness have been investigated for V₅₅Ti₃₀Ni₁₅ alloy by using hardness measurement, OM, XRD, SEM, EDS and TEM. The microstructures resulting from different heat treatment temperatures and time have a great influence on hardness. Fine NiTi particles precipitate from the V－based supersaturate solid solution when the alloys were heat treated at 750 and 800℃, and the amount of NiTi particles increases with time. Fine NiTi particles precipitate from the V－based supersaturate solid solution results in the decrease in hardness. With increasing temperatures, fine NiTi particles re－dissolve into V－based solid solution, and the alloys hardness increase instead. Solid solution hardening of Ni and Ti elements is greater than precipitation strengthening of fine NiTi particles formed by atomic binding of Ni and Ti in V₅₅Ti₃₀Ni₁₅ alloy. When the alloys were heat treated at 900℃, casting stress and lattice distortion decrease at heat treatment earlier stage, and then NiTi₂ phases start to aggregate and spheroidize on phase boundaries with extended time. This causes the phenomenon that the hardness first decrease and then increase.