粉末特性及热处理对选区激光熔化钛合金组织演变的影响

Effect of Powder Properties and Heat Treatment on Microstructure Evolution of Selective Laser Melted Titanium Alloy

通过粉末筛分和混合得到不同粒径分布的钛合金粉末,研究了粉末物理特性对选区激光熔化(selectivelaser melting,SLM)钛合金零件的打印质量、沉积态及热处理后微观组织的影响。结果表明,随细粉比例增加,粉末中位径下降,流动性下降,而松装密度变化不显著;3种粒径粉末打印后,成型零件的致密度均在99%以上,表面粗糙度随粉末中细粉含量的增加而下降,细粉量在23%时,孔隙率最小;成型后沉积态组织横截面为初生β晶粒,内部为针状马氏体α′,纵截面可见明显柱状晶;马氏体α′在600~800℃分解为片层α+β,且在800℃/4 h退火处理后α+β片层变粗。热处理时应严格控制退火温度和时间,避免片层粗化。

Titanium alloy powder with different particle size distribution was obtained by powder screening and mixing.The effects of physical properties of powders on the quality and deposited-and heat-treated-microstructure of selective laser melted(SLM) titanium alloy component were studied.The results show that with the increase in the proportion of fine powder,powder median size decreases,fluidity decreases while the bulk density does not change significantly;the relative density of parts from the powder with three kinds of particle sizes is more than 99%;the surface roughness decreases with the increase of fine powder content;when the quantity of fine powder is 23%,the minimum porosity forms after deposition;the as-deposited microstructure of the cross section is primary β grain,the internal is acicular martensite,and the longitudinal section is the visible columnar crystal;heat treatment results show that martensite decomposes to α+β layer at 600~800 ℃,and the α+β layer becomes thicker at 800 ℃.The annealing temperature and time during the heat treatment process should be strictly controlled to avoid layer coarsening.