高强钛合金层片组织拉伸变形中的裂纹萌生与扩展行为

Crack initiation and propagation mechanism in tensile deformation of Til300 alloy with lamellar microstructure after solution and aging treatment was investigated in detail, and the influence of grain boundary with Widmanstatten a phase (GBWa) on crack initiation and propagation was revealed. The results show that, the tensile fracture exhibits a mixed morphology of transgranular dimples and intergranular fracture facets, while the statistical analysis indicates a reduction in the number of intergranular fracture facets is related to an increase in the elongation of the alloy. By counting the locations of secondary crack initiation near the fracture, it is found that about 77% of secondary cracks near the fracture surface initiate predominantly at |3 grain boundaries, while about 23% of secondary cracks are initiated within p grains. By proposing a crack initiation strain parameter to assess the corresponding strain magnitudes for crack initiation, it is found that the strain parameter for cracks initiated at grain boundaries is lower than that for cracks initiated within p grains, which indicating a lower strain requirement for crack initiation at grain boundaries. As for cracks initiated at grain boundaries, 88% of them initiate at the grain boundaries without GBWa, while only 12% at those with GBWa, which indicating that the GBWa can inhibit the crack initiation. The crack propagation path in the fracture process is a mixture of extending through the grains and along the grain boundaries, and the GBWa can deflect the crack path.