Precipitation behavior and its impact on mechanical properties in an aged carbon-containing Al0.3Cu0.5CrFeNi2 high-entropy alloy

A cost-effective Al0.3Cu0.5FeCrNi2 high entropy alloy with carbon exhibits excellent balance of strength and ductility, i.e. high product of strength and elongation (35.3-51.4 GPa%) is achieved in the aged alloys. Three different types of precipitations have been found to precipitate at different temperatures. The study showed that the carbon content of 0.073 at.% was enough to promote the formation of M23C6 phase, which had a preference to precipitate at the grain boundary. With the contribution of M23C6 carbides, the yield strength and ultimate tensile strength of the sample aged at 900 degrees C increased by 193 MPa and 415 MPa, respectively, compared to the solid solutionized sample, while its elongation remained as high as 88%. Nanoscale L1(2)-ordered precipitates occurred in the alloy after aging at 700 and 550 degrees C. Cu-rich phase was only found in the alloy aged at 700 degrees C, and its precipitation kinetics is slower than that of the L1(2) phase. The synergetic strengthening of the coherent M23C6 carbides at grain boundaries and L1(2) and Cu-rich particles in the matrix of the alloys aged at 700 degrees C rendered the highest strength (904 MPa) while sustaining a high elongation of 39% at room temperature.