热处理对激光选区熔化TC4钛合金显微组织和力学性能的影响

研究了激光选区熔化(SLM) TC4钛合金沉积态和退火态显微组织的特征及其对力学性能的影响规律。结果表明:合金组织沿激光选区熔化成形高度方向呈现外延生长,形成柱状晶,晶内存在大量的针状马氏体α’相。退火后,晶内的针状α’相转变为α+β板条组织。随着退火温度的升高,组织中α相含量逐渐降低,α片层逐渐粗化,β相含量逐渐升高;室温拉伸强度逐渐降低,塑性逐渐升高,显微硬度逐渐降低。经过800℃×2 h/FC退火热处理后,激光选区熔化成形TC4钛合金具有最佳的强度与塑性匹配。

Influence of Heat Treatment on Microstructure and Mechanical Properties of TC4 Titanium Alloy Fabricated by Selective Laser Melting

TC4 titanium alloy was fabricated by selective laser melting( SLM). The influence of annealing treatment on the microstructure and mechanical properties were investigated in details. The results show that the microstructure as epitaxial growth columnar with fine acicular martensite phase. After annealing treatment,the microstructure changes from martensite phase to staggered basketweave α + β microstructure. With the increasing of annealing temperature,the content of α phase decreases,the size of α phase and the content of β phase both increases. With the increasing of annealing temperature,the room temperature tensile strength and micro-hardness decrease and the plasticity increases.The better strength/plasticity matching of TC4 titanium alloy formed by SLM can be obtained by the annealing heat treatment of 800 ℃ × 2 h/FC.