Relation between ductility and grain boundary character distributions in Ni₃Al

The grain boundary character distributions in cast, recrystallized and strain annealed Ni₃Al alloys with a composition of Ni23Al were examined to clarify the relation between ductility and the grain boundary character distributions in Ni₃Al. The percentages of CSL boundaries in cast, recrystallized and strain annealed Ni₃Al alloys are 26.8, 43.1 and 58.4%, respectively, of the total number of boundaries examined. The sum of the percentages for LAB (Low Angle Boundary) and Σ3 boundary in cast, recrystallized and strain annealed Ni₃Al alloys is 4.46, 10.8 and 29.2% respectively. This indicates that strain annealing is effective in enhancing the frequency of occurrence of CSL boundaries, especially LAB and Σ3 boundary, in Ni₃Al. The strain annealed Ni₃Al alloy having a much higher frequency of CSL boundaries is found to exhibit elongation to fracture of more than 45%. This significant increase in elongation of the strain annealed Ni₃Al alloys is attributed to the presence of relatively low energy LAB and Σ3 boundaries.