Effect of thickness and loading mode on the fracture properties of V–4Cr–4Ti at room temperature

Abstract

The effect of thickness on the room temperature (RT) mode I fracture behavior of V–4Cr–4Ti has been investigated. Mode I fracture properties were measured from J-integral tests of compact tension (CT) specimens ranging in thickness from 6.4 to 25.4 mm. All specimens were machined in the T–L orientation and vacuum annealed following final machining. Two heats of V–4Cr–4Ti were tested. Specimens 6.4 and 12.7 mm thick were taken from Wah Chang Heat No. 832665. The 25.4 mm thick specimens were obtained from Wah Chang Heat No. 832864. The effect of loading mode on fracture of V–4Cr–4Ti at RT was also studied using material from Heat No. 832665. Mode I fracture behavior was compared to mixed-mode (I/III) fracture properties obtained from modified CT specimens. Crack angles of 0° and 25° were used to vary the ratio of mode III to mode I loading. J– R curves were generated as the basis for determining the affect of loading mode. The specimen loaded in mixed-mode exhibited lower resistance to crack initiation and propagation than pure mode I specimens.