Fracture properties of high-purity V–4Cr–4Ti alloy (NIFS-HEAT-2) at room temperature

A high-purity vanadium alloy, V–4Cr–4Ti, NIFS-HEAT-2, was produced using electron beam melting and the vacuum arc re-melting process. The impurity was reduced to be as small as possible and a 26 mm thick plate was fabricated successfully. The normal size specimens were machined out of the plate to investigate the mechanical properties. Tensile tests and fracture toughness tests were conducted in air and in vacuum (about 10−4 Pa) environment at room temperature. The alloy showed high ductility and clear dimple fracture occurred in both environments. A ductile crack growth was not observed during the fracture toughness tests. The crack resistance curve went up straightly, and it was almost the same as the blunting line of which slope was 2×σflow. The blunting continued over several hundreds of J value in MJ/m2. The material is very tough and the valid J is not obtained at room temperature using a 12 mm thick compact tension specimen.