TA15钛合金疲劳裂纹扩展与显微组织的关系

Relationship of Fatigue Crack Propagation and Microstructure for TA15 Alloy

对TA15钛合金的疲劳裂纹扩展速率及其影响因素进行了研究。结果表明,在β区锻造的模锻件,其低倍组织为清晰可见的β晶粒,属于较粗大的网篮组织。在α+β区锻造的模锻件,其组织为双态组织。β区锻件的塑性偏低,但其da/dN疲劳裂纹扩展速率明显比α+β区锻件的慢。β区锻件的da/dN疲劳裂纹的断口形貌中,包括裂纹扩展的初期、中间阶段和末尾断裂阶段,都明显存在二次裂纹和解理脆性特征。

The fatigue crack propagation and its affecting factors for TA 15 alloy were studied. The results show that the macro-graph of β die forging displays the clear β grain with coarse net-basketlike structure. The micro-structure is hi-modal for the α＋β die forging. The ductility is low for the β die forging, but its fatigue crack propagation rate of da/aN-△K is lower than that of α＋β die forging. There exist secondary cracks and brittle cleavage planes in the fractographs of the initial, middle and ending stages of the fatigue fracture.