Effect of temperature, strain rate and impurity content on the work-hardening characteristics of lif single crystals

The work-hardening characteristics of LiF single crystals are investigated as a function of temperature and strain rate in high purity LiF and in LiF containing 800 p.p.m. Mg2+ impurity. It is shown that high purity crystals exhibit three stages of work hardening, depending upon temperature and strain rate. Both stage I and stage II work hardening are due to long-range, athermal dislocation interactions. Impurities suppress the three-stage work-hardening behaviour and give one linear stage of much higher work-hardening rate. These results indicate a close relationship between hardening mechanisms in LiF and in other ionic crystals.