Phase transformations occurring in Ni-rich NiAl during quenching

Abstract

Quenching of Ni-rich NiAl is accompanied by the formation of fine planar precipitates on {110} matrix planes and martensite is produced. Martensite is shown to have a body centred tetragonal crystal structure which can form from the high temperature NiAl B2 crystal structure by a process involving an inverse Bain correspondence. Since further ordering of martensite occurs during quenching a superordered martensite crystal structure is proposed. This structure is characterized by alternate stacking of Ni atoms and Ni or Al atoms on (011) planes. The martensite plates are internally twinned in {101}_T [101]_T.