Electronic and structural studies of grain boundary strength and fracture in L1₂ ordered alloys-III. On the effect of stoichiometry

In order to clarify the effect of alloy stoichiometry on the grain boundary strength and fracture behavior of L1₂-type A₃B compounds, the mechanical properties of Ni₃Al, Ni₃Ga, Co₃Ti and Ni₃(Al_0.52Mn_0.48) compounds were investigated at room temperature. Also, the effect of interstitial atoms of boron and hydrogen and the interaction of its effect with alloy stoichiometry were observed. The result indicated that the magnitude of compositional dependence of alloy stoichiometry on the elongation, the ultimate tensile strength and fracture behavior varied as Ni₃Al > Ni₃Ga > Co₃Ti > Ni₃(Al_0.52Mn_0.48). It was also revealed that the effect of interstitial atoms on the grain boundary cohesive strength is independent on and then additive to the effect of alloy stoichiometry. The significance of the grain boundary structure and related electronic environment in the grain boundary region was, in the geometrical frame, emphasized to interpret the present behavior.