Strength proof evaluation of diffusion-jointed W/Ta interfaces by small punch test

For the development of tantalum-clad tungsten targets for spallation neutron sources, the bonding strength of tantalum–tungsten interface was investigated by means of an easy-to-use and miniaturized small punch (SP) test, in which a punching load is vertically applied to the center of a jointed disk. Cracks initiated and propagated in the tungsten side for all the samples hot-isostatically pressed (HIPed) at temperatures from 1673 to 2073 K, whereas no crack and debonding were observed in the interface, indicating that the jointed interface is strongly bonded. The recrystallization of tungsten occurs and results in its strength reduction, consequently the crack-initiating load decreases with HIPing temperature. The finite element analysis of the measured SP testing results shows that the maximum bonding strength can exceed 1000 MPa. The present study shows that SP test is suitable for the strength evaluation of jointed tantalum–tungsten interfaces.