热处理对激光成形TC4合金组织及性能的影响

Influence of Heat Treatment on the Microstructure and Properties of Ti-6Al-4V Titanium Alloy by Laser Rapid Forming

通过对TC4钛合金激光快速成形件沉积态、去应力退火和固溶时效3种状态下的组织进行对比研究,探索改善TC4钛合金激光快速成形组织,提高材料综合力学性能的途径。结果表明,成形件的组织由贯穿多个熔覆层呈外延生长的粗大柱状晶组成,柱状晶主轴垂直于激光束扫描方向或略向光束扫描方向倾斜。原始的柱状β-Ti晶粒的微观组织是由极少量针状α,大量的魏氏α板条和一定体积分数的板条间β相组成。沉积态试样经退火处理后α板条有粗化趋势,性能改善不明显,塑性有所提高;经固溶时效热处理后可得到等轴α,网篮α和转变β相的三重混合组织,晶界α相被不同程度地破碎,甚至消失,塑性有明显提高,且强度降低不大,具有良好的综合力学性能。

The influence of heat treatment on the microstructures was investigated for Ti-6Al-4V alloy by laser rapid forming （LRF） process. The results indicate that the microstructures of sample by LRF consist of coarse columnar β grains with average grain width of 300 μm, which grew epitaxial from the substrate along the deposition direction Z. For the as-deposited samples, the microstructures of original β-Ti grains are composed of acicular a and Widmanstatten α laths and have an obvious tendency to coarsen by annealing treatment. And the microstructures consist of a triplex mixture of equiaxed α, basketweave α lath and transformed β by solution-aging treatment. The original and continuous α phase in the grain boundary was broken up and became un-integrated, even disappeared. Furthermore, the width of α laths increased and the aspect of α laths decreased. As a result, the room temperature tensile strength of the samples made by LRF are superior to that of the general forging sample （ASTM B381-05 ） , and the comprehensive mechanical properties are improved obviously through the solution-aging treatment.