A new thermodynamically stable Nb2Ni intermetallic compound phase revealed by peritectoid transition within binary Nb-Ni alloy system

A new intermetallic compound of thermodynamically stable NbNi phase is discovered within Nb-Ni binary system,refreshing the current situation that there are only three stable intermediate phases of NbNi,Nb Niand Nb Ni.The new stable phase is generated from the peritectoid transition:(Nb)+NbNi→NbNi,and the transformation temperature is 1533 K.This refreshes the current equilibrium Nb-Ni binary phase diagram.It is confirmed by transmission electron microscopy and the annealing experiments,which is determined to be the FCC structure (Pearson:c F96,space grope:Fd-3m O2,a=11.888 A).Furthermore,the equilibrium properties of NbNi phase are produced by density functional theory,including the formation energy,cohesive energy,bulk modulus and lattice constant.