The Effects of Dislocation Core Structure on Plastic Flow of L12 Ordered Alloys

The temperature dependence of the flow stress of strongly ordered L1₂ ordered alloys is of two basic types. One group of alloys, such as Ni₃Al, Ni₃Ge and Ni₃Ga, shows an increasing flow stress with increasing temperature, and the CRSS for {111}<101> slip of single crystalline samples depends strongly on the orientation and the sense of the applied uniaxial stress. A behavior of a second kind is seen in Pt₃Al. In this material the CRSS increases rapidly at low temperatures but is rather constant at elevated temperatures. Slip occurs on {111}<101> or on {010}<101>, depending on the sample orientation. These effects will be explained in terms of the nature of the dislocation core dissocation as determined from computer simulation experiments. It will be shown that the predicted behavior, based on the core structures determined from the simulations, agree remarkably well with the experiments.