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 °C increased by 193 MPa and 415 MPa, respectively, compared to the solid solutionized sample, while its elongation remained as high as 88%. Nanoscale L12-ordered precipitates occurred in the alloy after aging at 700 and 550 °C. Cu-rich phase was only found in the alloy aged at 700 °C, and its precipitation kinetics is slower than that of the L12 phase. The synergetic strengthening of the coherent M23C6 carbides at grain boundaries and L12 and Cu-rich particles in the matrix of the alloys aged at 700 °C rendered the highest strength (904 MPa) while sustaining a high elongation of 39% at room temperature.