多次激光冲击导致的Ti17合金层裂

为研究激光冲击Ti17合金中厚样品的层裂特性和层裂阈值，对样品（厚5 mm）表面进行单点连续1~8次激光冲击，激光工艺参数为:频率1 Hz，脉宽15 ns，激光能量30 J，方形光斑4 mm×4 mm。采用白光干涉仪、超声波无损检测技术和扫描电镜，分析和检测中厚样品冲击区域的表面形貌、内部损伤以及层裂形貌。实验结果表明，连续从4次到5次激光冲击中厚样品的表面凹坑深度增加值最大为64.5%。连续5次激光冲击为中厚样品层裂阈值，层裂面积随冲击次数增加而增加。连续5~8次激光冲击中厚样品层裂厚度的实验值为280~310 μm。层裂机理为韧性微孔洞的形核、增长和汇合，形成晶界失效和晶内失效。研究结果可为激光冲击强化整体叶盘改性提供工艺参考。

Spall of Ti17 alloy induced by laser shock peening with multiple shots

In order to investigate spalling response and the spall threshold of Ti17 alloy under laser shock peening (LSP), the surface of a 5 mm-thick sample was shocked by multiple laser shots with the shot number ranging one to eight shots. The laser employed has a repetition rate of 1 Hz, the pulse width of 15 ns, the pulse energy of 30 J, and the spot size of 4 mm×4 mm. The surface morphology, the internal damage and the spall morphology after LSP were characterized by non-contact optical profiler, ultrasonic nondestructive testing technique and scanning electron microscope, respectively. The results indicate that the increment of the shot number from four to five results in increasing the depression depth of the surface up to 64.5%. The spall threshold is reached by LSP with continuous five shots. The spall thickness observed after LSP with five to eight shots ranges from 280 μm to 310 μm. The spall mechanism is due to the nucleation, growth and coalescence of the ductile micro-voids, leading to intragranular failure and transgranular failure. This work may provide valuable information for the optimization of integrated blisk rotators with LSP.