【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<22.84MPa·m^1/2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^1/2时，二者具有相近的裂纹扩展速率，为3.92×10^-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。更多还原

【Abstract】 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. When ΔK < 22.84 MPa· m^1/2, the LSPed sample（BM-LSP） has a lower fatigue crack propagation rate than the un LSPed sample（BM）. When ΔK=22.84 MPa m^1/2, 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 secondary α layer are decreased by 38.9% and 22.9%, and the polar densities of α and β phases are decreased by 37% and 16%, respectively. The passivity of tip of the lamellar α and 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 900 μm 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.更多还原