Superplasticity in NiAl and NiAl-based alloys

Superplastic deformation was realized on NiAl and NiAl-based alloys prepared by both common casting and directional solidification. Directionally solidified NiAl–27Fe–3Nb alloy as well as conventionally cast NiAl, NiAl–25Cr, NiAl–9Mo, NiAl–20Fe–Y.Ce, and NiAl–30Fe–Y alloys exhibited typical deformation characteristics shown in conventionally superplastic materials. NiAl and NiAl-based alloys could be divided into three categories depending on their different superplastic behavior: finely grained structure (NiAl–9Mo, NiAl–25Cr, NiAl–20.4Fe–Y.Ce, NiAl–30Fe–Y), coarsely grained structure (NiAl), and columnar structure (NiAl–27Fe–3Nb). The corresponding deformation mechanisms for fine-grained structure, coarsely grained structure, and columnar structure were grain boundary sliding or grain boundary sliding accompanied by dynamic recrystallization, dynamic recovery and recrystallization, and intragrain dislocation slip, respectively.