激光冲击Ti834合金强化层显微组织演变

Microstructure Evolution of Ti834 Alloy Subjected to Laser Shock Processing in Strengthening Layer

激光冲击强化(laser shock processing,LSP)作为一种全新的表面强化技术凭借其强化效果好、可控性强、适应性好等优点在提高关键零部件服役寿命上发挥着不可替代的作用。本研究采用透射电子显微镜(TEM)观察LSP试样塑性变形层内显微组织结构特征的演变,构建了不同冲击次数下表层和深度方向上的显微结构演变示意图。结果表明,Ti834合金经激光冲击强化后塑性变形层内产生大量位错,且随着冲击次数的增加,塑性变形愈加剧烈,位错密度也进一步增加。沿深度方向上可以观察到随应变率递减而形成的典型微观结构特征,其中包括有形变孪晶(MTs),高密度位错墙(DDWs),位错缠结(DTs),位错阵列(DAs)和位错线(DLs)等。

Laser shock processing(LSP),also known as laser peening,is a novel surface strengthening treatment technology,which is capable of introducing residual compressive stress,improving performance of fatigue strength and micro-hardness.With its preferable reinforcement effect,strong controllability and outstanding adaptability,LSP plays an irreplaceable role in improving the service life of key components.The evolution of microstructure in the plastic deformation layer of Ti834 alloy subjected to LSP impacts was investigated by transmission electron microscopy(TEM),and the microstructure evolution model in the surface layer and along depth direction was established.The results indicate that numerous dislocations are generated in the plastic deformation layer of Ti834 alloy subjected to LSP,and the plastic deformation becomes more intense and the dislocation density further increases as the number of impacts increases.Typical microstructure features due to decreasing strain rates can be observed along the depth direction,including mechanical twins(MTs),dense density dislocation walls(DDWs),dislocation tangles(DTs),dislocation arrays(DAs)and dislocation lines(DLs).