The initiation and continuation of plastic strain in NiAl and Ni3Al studied by anisothermal creep and stress relaxation experiments

The initiation and continuation of plastic strain in NiAl and Ni3Al single crystals have been studied by anisothermal creep tests and stress relaxation tests coupled with in situ electrical resistance measurement. Anisothermal creep tests of NiAl single crystals in the “dislocation-free” [001] orientation show that the plastic strain is initiated at a well-defined critical temperature. In Ni3Al, the development of dislocation density during stress relaxation is monitored with in situ electrical resistance measurement. Below the yield strength peak, where the yield strength increases anomalously with temperature, the dislocation density decreases with relaxation plastic strain. Above the yield strength peak, where the yield strength of Ni3Al exhibits a normal decrease with temperature, the dislocation density increases with the relaxation plastic strain.