Compressive mechanical properties of multi-phase alloys based on B2 CoAl and E21 Co3AlC

Mechanical behavior of multi-phase alloys, consisting of intermetallic compounds B2 type CoAl and E21 type Co3AlC with primary solid solution (Co), was investigated by compression tests over a wide temperature range from 77 to 1273 K. It has been revealed that E21 Co3AlC is a good candidate of coexisting phase with B2 CoAl to improve the alloyʹs ambient temperature ductility and its elevated temperature strength. Most of the multi-phase Co–Al–C ternary alloys exhibit fairly good compressive ductility at whole test temperatures, even at 77 K. All the alloys show the anomalous positive temperature dependence of strength at intermediate temperatures. The deformation mechanism of E21 Co3AlC is expected to be the same as that of L12 intermetallic compounds because of the close resemblance of their crystal structures. The three-phase B2/E21/(Co) alloy, 70Co20Al10C(at%), exhibits excellent ductility of virtually unlimited ambient temperature compressive plastic strain and the highest strength around 340 MPa at 1273 K.