Abstract
The fracture properties of grain boundaries in binary stoichiometric Ni3Al were studied by performing tensile tests at room temperature in air on miniature bicrystal specimens with various grain-boundary types, namely. ∑ = 1, ∑ = 3, ∑ = 5, ∑ = 1, ∑ = 9, ∑ = 13a and random boundaries (RBs). All the specimens exhibited some tensile ductility prior to fracture. A fairly good relationship was found between fracture mode, fracture strength and ∑ value. The ∑ = 1, ∑ = 3 and ∑ = 9 boundaries were strongly crack resistant and the adjacent bulk fractured instead. In contrast, the ∑ = 5, ∑ = 7 and ∑ = 13a boundaries and RBs were less crack resistant, showing a typical intergranular fracture. The fracture strength of these boundaries was low and widely varied with the orientation of the component grains and the grain-boundary plane. The cohesive strengths of ∑ = 1, ∑ = 3 and ∑ = 9boundaries were estimated to be high in comparison with that in bulk Ni3Al, that of RBs much smaller and those of ∑ = 5, ∑ = 7 and ∑ = 13a boundaries slightly larger than that of RBs.