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

Highlights: • 0.073 at. % C can introduce M₂₃C₆ in an aged high-entropy alloy. • High product of strength and elongation was achieved. • Synergetic strengthening of different particles benefits the mechanical properties. -- Abstract: A cost-effective Al_0.3Cu_0.5FeCrNi₂ 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.