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

Mechanical properties of E21 based Co3AlC single crystals and single-phase polycrystalline Co3AlC and Fe3AlC 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 Co3AlC single crystal. Yield strength anomaly appears in Co3AlC single crystal as we have expected from the similarity between E21′ and L12. 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.