Effect of Al content on the fracture toughness and deformation behavior of Ti-Al binary alloys

The fracture toughness and deformation behavior of Ti- x Al ( x = 0, 2, 4 wt%) binary alloys were investigated. The non-thickness-dependent fracture toughness was measured based on the J-integral multiple-sample approach. Increased Al content induced reduced fracture toughness from 265 to 148 MPa & sdot; m 1/2 of Ti- x Al alloys. The fracture toughness was discussed in this article by the mutual influence of the elastic component ( J el ) and the plastic component ( J pl ). The solid solution strengthening effect of Al was identified as the primary factor contributing to the increase in J el . Additionally, the evolution mechanism of J pl with varying Al content was elucidated by slip modes, twin activation, and dislocation configurations at the crack tip. Prismatic slip was found to be the predominant slip mode in Ti- x Al alloys. With the increase in Al content, the elevated critical resolved shear stress associated with prismatic slip hindered the alleviation of stress concentration, resulting in a decrease in J pl . The increase in content of Al in the Ti- x Al alloys inhibited the formation of {11 2 2} twins. Compared to Ti-0Al and Ti-2Al alloys, a significant increase in c c a dislocations, which potentially resulted in a reduction in J(pl) . Furthermore, a crack tip stress analysis method based on twin variant activation was proposed. In Ti-0Al and Ti-2Al alloys, twins activated by internal stress were more pronounced compared to the Ti-4Al alloy. The internal stress may be composed of back stresses, which are generated by twinning activation.