Role of microstructure in plastic deformation and crack propagation behaviour of an α/β titanium alloy

The deformation and crack propagation behaviour have been comparatively investigated in a titanium alloy with bimodal microstructure (BM) and bilamellar microstructure (BLM). The results show that higher fracture toughness (58 MPa m(1/2)) was obtained for the BLM than that BM one (45 MPa m(1/2)). The deformed microstructure, crack initiation and propagation and surface damage morphology were observed by SEM and EBSD. Fatal cracks easily nucleated at the larger primary alpha phase, especially at the equiaxed alpha(e)/beta interface and primary alpha lath (alpha(l)), and often grow along a straight line, which accelerated the crack propagation and leaded to non tortuous crack path in BM. For the BLM, slip hardly transferred the alpha(l)/beta(trans) interface due to the secondary alpha(alpha(s)) precipitation in the beta lamellas. Cracks initiated at the boundaries of alpha colony and propagated with a zig-zag way, which leaded to a high branch and fluctuation of the crack of BLM and generated a relatively superior fracture toughness performance. These results indicate that a small amount of alpha(l) colony surrounded with beta(trans) matrix is beneficial to the improvement of fracture toughness, which can provide a good theoretical support to tailor the microstructure and mechanical performance of titanium alloys.

Automated summary

Comparative study on deformation and crack propagation in a titanium alloy with bimodal and bilamellar microstructure showed that the bilamellar microstructure exhibited higher fracture toughness due to the secondary alpha precipitation and zig-zag crack propagation. The presence of a small amount of alpha colony surrounded by beta matrix is beneficial for improving fracture toughness in titanium alloys.