EFFECT OF TEMPERATURE AND STACKING-FAULT ENERGY ON THE HARDENING OF FCC CRYSTALS

A model to account for the temperature and stacking fault energy in th e hardening of FCC metal single crystals is presented. Temperature and stacking fault energy are considered to affect primarily the cross-sl ip rate and the obstacle strength given by the forest dislocation. The essential experimental features are captured by the model. For high s ymmetry loading axes, the stress-strain curves for all temperatures sh ow a similar initial high hardening slope, followed by a parabolic har dening. The initiation of the parabolic hardening is dictated by the t emperature as shown in the experiments. For low symmetry loading, the extent of stages I and II, the hardening slope and the initiation of s tage III are functions of temperature. The higher the temperature. the shorter the extent of stages I and II and the lower the hardening slo pe and the stress at the initiation of parabolic hardening. On the oth er hand, a high stacking fault energy reduces the extent of stages I a nd II and the levels of latent hardening, in keeping with the experime ntal observations.