表面激光冲击对双态组织Ti55531钛合金疲劳裂纹扩展速率的影响  

Effect of Surface Laser Shock on Fatigue Crack Propagation Rate of Bimodal Structure Ti55531 Titanium Alloy

作　　者：史蒲英 陈林[3] 刘向宏 庞智聪[1] 何卫锋 李芹芹 李应红 Shi Puying;Chen Lin;Liu Xianghong;Pang Zhicong;He Weifeng;Li Qinqin;Li Yinghong(Institute of Aeronautics Engine,School of Mechanical Engineering,Xi’an Jiaotong University,Xi’an 710049,China;Western Superconducting Technologies Co.,Ltd,Xi’an 710018,China;School of Materials Science and Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学机械工程学院航空发动机研究所,陕西西安710049 [2]西部超导材料科技股份有限公司,陕西西安710018 [3]西安交通大学材料科学与工程学院,陕西西安710049

出　　处：《稀有金属材料与工程》2024年第10期2823-2830,共8页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(52205240);中国博士后科学基金(2022M723874);陕西省创新能力支撑计划(2022KJXX-84)。

摘　　要：对激光冲击(LSP)前后双态组织Ti55531钛合金的疲劳裂纹扩展速率(da/dN)进行了研究。分析了激光冲击前后疲劳裂纹扩展样品的断口、微观组织和残余应力。结果表明,经过激光冲击,双态组织Ti55531钛合金的da/dN降低,当△K<22.84 MPa·√m时,激光冲击后样品(BM-LSP)具有比未冲击样品(BM)更低的疲劳裂纹扩展速率,当△K=22.84 MPa·√m时,二者具有相近的裂纹扩展速率,为3.92×1^(-4) mm/cycle。LSP后次生α相片层厚度离散性降低38.9%,长度离散性降低22.9%,α相和β相的极密度分别降低37%和16%。LSP后次生α相片层尖端钝化和组织均匀化是缓解疲劳裂纹尖端应力集中,导致da/dN下降的主要因素。此外,激光冲击过程中在材料表面引入深度约900μm的残余压应力层。残余压应力也是抵消裂纹尖端拉应力、增强裂纹闭合、减缓裂纹扩展速率的重要因素。The fatigue crack propagation rate(da/dN)of bimodal structure Ti55531 titanium alloy before and after laser shock peening(LSP)was investigated.The fracture,microstructure and residual stress of fatigue crack propagation samples were analyzed.The results show that after LSP,the fatigue crack propagation rate decreases.WhenΔK<22.84 MPa·√m,the LSPed sample(BM-LSP)has a lower fatigue crack propagation rate than the unLSPed sample(BM).WhenΔK=22.84 MPa m,the crack propagation rates of the two samples are similar,which are 3.92×10^(-4) mm/cycle.After LSP,the thickness dispersion and length dispersion of the secondaryαlayer are decreased by 38.9%and 22.9%,and the polar densities ofαandβphases are decreased by 37%and 16%,respectively.The passivity of tip of the lamellarαand microstructure homogenization alleviate the stress concentration,resulting in a decrease in da/dN.In addition,the LSP process introduces a residual compressive stress layer with a depth of about 900μm on the surface of the material.Residual compressive stress is also an important factor to offset tensile stress at crack tip,to enhance crack closure and to slow down crack propagation.

关 键 词：Ti55531钛合金 表面激光冲击 疲劳裂纹扩展速率(da/dN) 微观组织 

分 类 号：TG174.4[金属学及工艺—金属表面处理] TG146.23[金属学及工艺—金属学]