Extra ordering of carbon atoms and mechanical properties of E21 Co3AlC based heat resistant alloys

Abstract Mechanical properties of E2 1 based Co 3 AlC single crystals and single-phase polycrystalline Co 3 AlC and Fe 3 AlC alloys have been evaluated by compression tests performed in a wide temperature range from room temperature to 1373 K. Effect of the ordering of C on the phase stability and mechanical properties has been investigated and discussed with the anti-phase boundary (APB) formation. Temperature dependence of critical resolved shear stress (CRSS) has been determined to consider the compressive mechanical behavior of Co 3 AlC single crystal. Yield strength anomaly appears in Co 3 AlC single crystal as we have expected from the similarity between E2 1 ′ and L1 2 . Schmid law is only applicable in a high temperature range between 1173 and 1273 K. Crystallographic analysis and microstructure observation were conducted using transmission electron microscopy (TEM). It was found that disordering of C atoms could be induced by the irradiation damage of electron beam after high-resolution transmission electron microscopy (HRTEM) observation.