不同热处理对激光定向能量沉积制造TC4钛合金组织和拉伸性能的影响

Effect of Different Heat Treatments on Microstructure and Tensile Properties of TC4 Titanium Alloy Fabricated by Laser Directed Energy Deposition

激光定向能量沉积技术(Directed energy deposition,DED)是一种逐点逐层熔化沉积从而直接制造致密金属零件的高性能加工成形技术。由于其制造的TC4钛合金的显微组织与传统锻件有很大的不同,选用合适的热处理工艺是改善其力学性能的关键。因此,研究了三种不同热处理制度对DED制造TC4钛合金对成形构件晶粒形貌、显微组织和室温以及高温拉伸性能的影响。研究结果表明,经过600℃和800℃退火处理后,α片层均出现不同程度的粗化,且α相含量略微提高,经975℃双重退火处理后生成了部分等轴α相,室温拉伸塑性得到改善,与800℃退火处理试样相比,横向面缩率增加了约26.1%。在400℃高温拉伸时,975℃双重退火后的合金具有最高的横向平均高温断后伸长率,表现出优异的高温强度-塑性匹配。

Laser directed energy deposition(DED)is a manufacturing technology for producing high performance fully dense near-net metallic components,which is melting metal powders point by point and stacking them layer by layer.Since the microstructure of DEDed TC4 titanium alloy is different from that made by traditional forging,selecting appropriate heat treatment process can improve its mechanical properties significantly.The effects of three different heat treatment on microstructure morphologies and tensile properties of DEDed TC4 alloy were investigated.The results show that after 600℃and 800℃annealing treatment,theαlamellae coarsens to different degrees,and the volume fraction ofαphase increases slightly.The double annealing heat treatment at 975℃results in the appearance of equiaxedαphase,improving room-temperature plasticity with about 26.1%higher in average transverse reduction of area than that after 800℃annealing treatment.After double annealing heat treatment at 975℃,TC4 alloy has the highest transverse average elongation at high temperature tensile test at 400℃,showing excellent high temperature strength-plastic balance.