Strengthening and deformation mechanism of a Fe₂₀Co₂₀Cr₂₀Mn₂₀Ni₂₀ high entropy alloy with high nitrogen content

In this investigation we prepared samples of Cantor alloy, i.e. Fe₂₀Co₂₀Cr₂₀Mn₂₀Ni₂₀ and re-melted them in a nitrogen-argon atmosphere by electric arc to dissolve nitrogen into the ingot, followed by aging for 24 h at 800 °C to precipitate nitride in the ingot. The microstructure, hardness and compressive strength of the three fabricated alloys were characterized and compared. Inductively coupled plasma (ICP) measurement found that high nitrogen content of 3.51 at% was successfully dissolved in the ingot, which is significantly higher than the nitrogen contents in most of the nitrogen-doped high entropy alloys reported so far. The ingot preserved the typical single-phase, face-centered cubic structure of Cantor alloy. After aging the ingot at 800 °C for 24 h, lamellar Cr₂N precipitates were found and its volume fraction was estimated to be 3.6%. The Vickers’ hardness of nitrogen-dissolved and aged alloy was increased from 133 HV to 235 HV and 262 HV respectively, while their yield strength increased from 192 MPa to 336 MPa and 416 MPa, respectively.