Laser powder bed fusion processing of a precipitation strengthenable FCC based high entropy alloy

While additive manufacturing (AM) of single-phase solid solution based high entropy alloys (HEAs) has attracted a lot of recent attention, such processing of precipitation strengthenable multi-phase HEAs has not been actively investigated. This becomes important since AM processing results in each layer experiencing rapid solidification followed by multiple heating-cooling cycles, mimicking in situ heat treatments, potentially influencing the phase evolution. A precipitation strengthenable face centered cubic (FCC) based HEA, Al0.3Ti0.2Co0.7CrFeNi1.7, was printed using laser powder bed fusion (LPBF), resulting in predominantly FCC grains with internal solidification cells, and small pockets of a mixed BCC + B2 phase microstructure in the inter-cellular regions. Early stages of ordered L1 2 precipitation was also observed within the FCC grains, containing a large fraction of low angle sub -grain boundaries. While the as-built alloy exhibited a yield strength of -600 MPa with 15% ductility at room temperature, after ex situ annealing at 800 & DEG;C for 5 hrs, the yield strength increased to -950 MPa.