Creep of anomalous Ni3Ga

Ni3Ga is among a number of Ll(2) ordered intermetallic alloys whose yield stress increases with temperature. In this work we have examined the creep strength of [(1) over bar 23] and [001] oriented Ni3Ga specimens in the temperature regime of the yield stress anomaly and confirmed that the creep strength shows the normal rapid decrease with temperature. Inverse creep occurs in the [001] specimens where slip is on the {111} planes only. [(1) over bar 23] specimens exhibit steady-state creep and slip line and TEM observations have shown slip on the cube plane and dislocations of both [110] and [100] Burgers vectors are present. We have carried out creep tests of prestrained [(1) over bar 23] samples and demonstrated that the storage of primary [110]{111} screw dislocations, locked in the Kear-Wilsdorf configuration, has no effect on creep.