First-principles study on the ductility effect of zirconium and its distinct behavior from boron to restrain hydrogen-induced embrittlement in Ni-Ni3Al alloys

By studying a cluster model containing Ni region (phase), Ni3Al region (phase) and Ni/Ni3Al region (interface) with a first-principles method, the occupation behavior and the ductility effect of zirconium in a Ni-Ni3Al system were investigated. It is found that zirconium has a stronger segregation tendency to Ni region than to Ni3Al region. The bond order analyses based on Rice-Wang model and the maximum theoretical shear stress model, however, show that zirconium has different degrees of ductility effect in these three regions, which originates from its different ability to increase the Griffith work of interfacial cleavage 2(gamma int) and to decrease the maximum theoretical shear stress tau(max). In addition, it is revealed in this paper that the distinct behavior of zirconium from boron to restrain hydrogen-induced embrittlement can be attributed to their different influences on the crystalline and electronic structures in Ni-Ni3Al alloys.