Nonequilibrium phases formation by mechanical alloying of A(3)B powders and relation between mechanical properties and ordering energies of Ni3Al

Structural changes of A(3)B type elemental powders (Ni75Al25, Co75Ti25, Fe75Ge25, Ni75Si25 and Ni75Ge25) by mechanical alloying were investigated by X-ray diffractometry (XRD). An amorphous phase and a metastable bcc phase was formed by MA of Co75Ti25 and Fe75Ge25 respectively. On the other hand, metastable fee phases were formed by MA of the other powders. Nonequilibrium phases other than Fe75Ge25 transformed to the L1(2) phases by heating to 873 K, while Fe75Ge25 changed to L1(2) + bcc phases. Furthermore, the effect of the ternary elements on the ordering temperatures and the ordering enthalpy of mechanically alloyed fcc-Ni3Al was investigated to make clear the relation between mechanical properties and the ordering energy of Ni3Al.