Unusually increased plasticity of additively manufactured ultra-strong CoCrNi medium entropy alloy composite with increasing temperature

We obtained the CoCrNi alloy composite with TiC fraction as high as 5 wt% by laser powder bed fusion (LPBF) of blended powder of Ti, C and CoCrNi medium entropy alloy (MEA). The as-built composite shows ultra-strong strength ranging from 2245 MPa to 1639 MPa and increasing fracturing strain from 8.5 % to 20 % at temperature ranging from 77 K to 873 K. The significantly increased plasticity is mainly attributed to the higher and stabler straining hardening rate at elevated temperature compared to at room temperature, which is induced by the increasing number of deformation-induced nano-twins and stacking faults with the increasing deformation temperatures. This abnormal phenomenon is supposed to result from the increasing shearing ability of the stacking faults (SFs) on the gamma' phase with temperature and the strengthening effect of the nano-TiC along the cell walls.