热处理工艺对Ti-6Al-4V钛合金点阵结构显微组织和性能的影响

Effect of Heat Treatment Process on Microstructure and Performance Ti-6Al-4V Titanium Alloy Lattice Structure

采用选区激光熔化技术制备了Ti-6Al-4V钛合金点阵结构,并进行了700℃、800℃和900℃保温2h炉冷的热处理。检测了点阵结构的表面形态、微观结构和压缩性能,并与制备态点阵结构作了比较。结果表明:Ti-6Al-4V点阵结构具有较高的表面粗糙度,其组织由细小的针状α′马氏体和初生柱状β相组成;热处理后,α′马氏体分解为α+β混合片层组织,且加热温度越高α′马氏体分解越完全,α相粗化越明显;不同热处理工艺后的点阵结构具有相似的压缩变形过程,原始态点阵结构塑性的差异导致了45°角坍塌带形成时压缩应变水平的不同;热处理后点阵结构的弹性模量和强度下降,但能吸收更多的能量。经900℃×2h炉冷的Ti-6Al-4V钛合金点阵结构更适合制作汽车吸能盒。

The Ti-6Al-4V titanium alloy lattice structure was fabricated by a selective laser melting(SLM)technology,and was heat treated by heating at 700℃,800℃and 900℃for 2 h followed by furnace cooling.Surface morphologies,microstructures and compression performance of the lattice structure were detected,and compared with those of as-fabricated one.The results showed that(a)the Ti-6Al-4V lattice structure exhibited higher surface roughness,and microstructure consisting of fine needle-type α’martensite and primary columnar β phase;(b)after the heat treatment,α’martensite decomposed into a lamellar mixture consisting ofαphase andβphase,the higher the heating temperature,the more complete the decomposition ofα’martensite was,and the coarser theαphase was;(c)the lattice structures heat treated by different procedures had a similar compression deformation process,the difference in plasticity of the primary lattice structure resulted in the difference in level of compression strain at the time of the 45°angle collapse zone being formed;and(d)after heat treatment,the lattice structure offered decreased both elastic modulus and strength,but permitted absorbing even more energy.The Ti-6Al-4V lattice structures heated 900℃for 2 h and then furnace cooled is even more suitable for car energy absorbing box.