Mechanical Behavior of Lithium Fluoride at High Temperatures

Abstract

Single crystals of lithium fluoride were pulled in tension at high temperatures; the results of these tests are compared with data for magnesium oxide. Interpenetration of {110}〈110〉 slip systems does not occur in LiF as readily as in MgO. Because of this lack of interpenetrability, plastic instability and completely ductile fracture do not occur in LiF below 700°C (0.87 Tmp); the high‐temperature tensile strength of LiF decreased very little from 300° to 700°C. This lack of interpenetrability of slip systems in LiF at high temperatures also had a profound effect on the deformation processes, the development of substructure, and the strain‐hardening and fracture characteristics of the material. This work emphasizes the importance of interpenetration of slip not only in the high‐temperature ductility and strain‐hardening processes but also in the maximum tensile strength which ionic crystals develop before fracture.