Temperature dependence of the flow stress of Ir-based L12 intermetallics

The temperature dependence of compressive strength of Ir3Zr, Ir3Hf, and Ir3Ti with an L12 structure was investigated. Ir3Zr showed weak anomalous behavior; in other words, the strength increased up to a peak strength with increasing temperature at intermediate temperatures but decreased slightly with increasing temperature below room temperature. Ir3Ti and Ir3Hf showed normal strength behavior. Their strength behavior including Ir3Nb is discussed in terms of the phase stability of the L12 structure with respect to other related structures. The lower phase stability of Ir3Ti with respect to the D024 phase suggests stable SISF-bounding dislocations, which cause the normal strength behavior to occur. The lower phase stability of Ir3Nb with respect to the D0a causes anomalous behavior at intermediate temperature.