The roles of microstructure in plastic deformation and crack growth mechanisms of a titanium alloy with a trimodal microstructure have been systematically investigated. The results show that thick intragranular α lath and a small number of equiaxed α phases avoid the nucleation of cracks at the grain boundary, resulting in branching and fluctuation of cracks. Based on electron back-scattered diffraction, the strain partition and plastic deformation ahead of the crack tip were observed and analyzed in detail. Due to the toughening effect of the softer equiaxed α phase at the grain boundary, crack arresting and blunting are prevalent, improving the crack growth resistance and generating a relatively superior fracture toughness performance. These results indicate that a small amount of large globular α phases is beneficial to increase the crack propagation resistance and, thus, a good combination of mechanical property is obtained in the trimodal microstructure.

中文翻译：

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具有三峰微结构的α+β钛合金的抗裂纹扩展性能的提高

已经系统地研究了微结构在具有三峰微结构的钛合金的塑性变形和裂纹扩展机理中的作用。结果表明，较厚的晶内α板条和少量等轴α相避免了晶界处裂纹的成核，导致裂纹的分支和波动。基于电子背散射衍射，观察并详细分析了裂纹尖端处的应变分布和塑性变形。由于较软的等轴α相在晶界处的增韧作用，裂纹的阻止和钝化普遍存在，改善了裂纹扩展的抵抗力，并产生了相对优越的断裂韧性。