激光冲击强化TC17钛合金室温和高温拉伸性能研究  

Tensile Properties at Room and High Temperature of TC17 Titanium Alloy Treated by Laser Shock Peening

作　　者：曹子文[1] 杨清[2] 高宇[2] 

机构地区：[1]北京航空制造工程研究所高能束流加工技术重点实验室,北京100024 [2]沈阳黎明航空发动机(集团)有限责任公司,沈阳110043

出　　处：《表面技术》2018年第3期85-90,共6页Surface Technology

摘　　要：目的分析激光冲击强化对钛合金室温和高温拉伸性能的影响。方法用YAG纳秒脉冲激光器对TC17钛合金板状拉伸试样表面进行双面激光冲击强化,脉冲能量为25 J,脉冲宽度为15 ns,光斑尺寸为4.2 mm×4.2 mm,搭接率为10%,强化1次。通过室温及400℃下拉伸试验,获得强化前后试样的抗拉强度、屈服强度和断裂伸长率,利用X射线衍射法测试拉伸前后试样表面的残余应力,并在扫描电镜下观察拉伸试样断口微观形貌。结果室温拉伸试验时,激光冲击强化对TC17钛合金的室温抗拉强度和伸长率几乎无影响,但强化后的室温屈服强度下降约6.1%,有/无强化试样均没有明显的屈服点,距离强化试样断裂位置10 mm的表面残余压应力较拉伸前下降约12%。400℃拉伸试验时,激光冲击对TC17钛合金的高温抗拉强度和屈服强度均影响较小,有/无强化试样均出现明显的屈服点,距离强化试样断裂位置10 mm的表面残余压应力较拉伸前下降约44%。结论激光冲击强化在TC17钛合金表面引入显著的残余压应力分布,对屈服强度具有一定程度的影响。强化后试样的屈服强度与拉伸过程中残余压应力松弛速率有关,室温拉伸过程的残余应力松弛较高温拉伸过程慢,试样内部的平衡拉应力区更容易先发生屈服。这是造成室温拉伸屈服强度小幅降低的主要原因。The work aims to analyze effects of laser shock peening （LSP） on tensile properties at room and high temperature of titanium alloy. Plate-shaped TC17 titanium alloy tensile samples were dual-side laser shocked once by a YAG ns-pulse laser, with pulse energy of 25 J, pulse width of 15 ns, spot size of 4.2 mm×4.2 mm and overlapping rate of 10%. Tensile tests were performed at room temperature and 400 ℃ to obtain yield strength, tensile strength and elongation at break of the samples before and after LSP. Residual stress on sample surface was tested in X-ray diffraction method, and fracture microstructure of the tensile samples was observed with SEM. In the tensile test at room temperature, tensile strength at room temperature and elongation of TC17 titanium alloy were almost not affected by laser shock peening, but yield strength at room temperature decreased by nearly 6.1% after LSP, and there was no obvious yield point on the samples receiving LSP or not, and surface residual compressive stress 10 mm from sample failure position decreased by nearly 12% than that before stretching. In the tensile test at 400 ℃, tensile strength at high temperature and yield strength of the TC17 titanium alloy were slightly affected by laser shock peening, there were obvious yield points on the samples receiving LSP or not, and surface residual compressive stress 10 mm from sample failure position decreased by nearly 44% than that before stretching. Yield strength is affected to a certain extent as significant residual compressive stress is induced by LSP on TC17 titanium alloy. Yield strength of the peened samples closely relates to relaxation rate of residual compressive stress during stretching. The relaxation of residual stress during stretching at room temperature is slower than that during stretching at 400 ℃. As a result, balance tensile stress zones inside the samples are more likely to yield, which explains slight yield strength decrease at room temperature.

关 键 词：拉伸性能 激光冲击强化 方形光斑 残余压应力 应力松弛 TC17钛合金 

分 类 号：TG156.99[金属学及工艺—热处理]