In-situ SEM observation on the fracture of V-5Cr-5Ti alloy

The damage and fracture characteristic of V-5Cr-5Ti (wt.%) alloy was investigated using scanning electron microscope (SEM) with a micro-tension holder. Two types of specimen were used: smooth sheet and single-edge notched sheet. Results show that the microscopic fracture mechanism of smooth sheet alloy is microvoid coalescence and sliding off. What the fracture process shows is that the damage of smooth specimen stems from the inside. The alloy can be strengthened by single-edge notch but still remains considerable ductility. The main fracture mechanism of notched specimens is sliding off and quasi-cleavage. The main crack initiates at the root of notch and propagates along a zig-zag path. Grain boundary is a main barrier for crack propagation. Finite element method (FEM) simulation shows that the crack growth relaxes the stress of notched specimen, which in turn changes the fracture mechanism of alloy.