激光冲击强化提高TC4叶片振动疲劳性能

针对典型钛合金TC4进行激光冲击强化(LSP)参数设计,对强化后残余应力分布规律进行测量,应用透射电子显微镜对强化后表层微观组织进行观察,对有无LSP钛合金叶片进行不同应力水平下的振动疲劳对比试验。研究表明,TC4钛合金LSP最佳功率密度为3.5GW/cm2,LSP在材料表层产生高数值的残余压应力场,表面残余应力可达-610MPa,最大值约-650MPa位于距离表面100μm处。LSP在钛合金表层产生纳米晶,纳米晶尺寸在几个至几十纳米。钛合金叶片LSP后疲劳极限由430 MPa提高至560 MPa,升高30%;在560MPa应力水平下,中值疲劳寿命提高为原来的200%以上;LSP在钛合金表层产生的残余压应力场和纳米晶共同作用显著提高了钛合金叶片的抗疲劳性能。

Improvement of Vibration Fatigue Performance on LSP Processed TC4 Blade

The laser shock peening(LSP) parameters to process TC4 titanium alloy were studied.The characteristics of the residual stress distribution were tested by XRD,and the microstructure after LSP was measured by TEM.And then,viberation fatigue test under different stress was carried out on TC4 blade.The results show that the optimal power density to process TC4 titanium alloy is 3.5 GW/cm2.The residual stress on material surface could reach-610MPa when high residual stress field is induced by LSP.The maximum residual stress is-650MPa about 100μm in depth.The TEM measurement shows that high nanocrystalline is produced by LSP,the size of which ranges from several to dozens of nanometers.The fatigue limit of TC4 blade is improved by LSP from 430 MPa to 560 MPa,about 30% higher to the one without LSP treatmemt.The medium fatigue life increases more than 200% when the stress is 560 MPa after LSP.The residual stress induced by LSP adjoint with the nanocrystal on the surface together enhanced the fatigue ability of TC4 blade.