Strengthening and deformation mechanism of interstitially N and C doped FeCrCoNi high entropy alloy

In this investigation, FeCrCoNi high entropy alloys doped with 0.5 at%, 1 at%, 2 at% C and 0.48 at% N, respectively, were prepared by arc melting followed by homogenization for 1 hr at 1100 °C. The deformed microstructure and compressive strength of these alloys were characterized and compared. The ingots with 0.48 at% N and 0.5 at% C retained the typical single-phase, face-centered cubic structure. In samples with 1 at% C and 2 at% C, M₂₃C₆ precipitates were found. Comparing with FeCrCoNi alloy, the yield stress of N doped FeCrCoNi was increased from 132 MPa to 202 MPa while that of 0.5 at% C doped was only increased to 152 MPa. For 1 at% C and 2 at% C alloys, the yield stresses were increased to 195 MPa and 327 MPa respectively. In the early deformation stage, the N doped alloy showed pure planar slip while that of 0.5 at% C doped and undoped FeCrCoNi showed both planar slip and wavy slip. At higher strain (50% compression strain), twinning and wavy slip prevailed in samples with 0.5 at% C and undoped alloy, while that of N doped alloy showed both wavy slip and planar slip. Wavy slip prevailed in all deformation stage and twinning was found at later deformation stage in 2 at% C doped alloys.