Microstructure and mechanical properties of Co-free Ni2FeCrWx medium-entropy alloys reinforced by coherent precipitates

In the present work, novel Co-free Ni2FeCrWx medium-entropy alloys (MEAs) are designed by equiatomically replacing Co with Ni in the CoCrFeNi high-entropy alloys (HEAs). The effects of W addition coupled with subsequent heat treatment on microstructure evolution and mechanical properties were systematically investigated and analyzed. The W-addition is conducive to the formation of & mu; phase in Ni2FeCrWx MEAs, while the annealing treatment promotes the precipitation of submicron-sized BCC particles and the spheroidization of & mu; phase. The orientation relationship (OR) of [1210]& mu; phase // [011]FCC and (3030)& mu; phase // (111)FCC and the coherent interface is formed between & mu; phase and FCC matrix in as-cast alloys, and the orientation relationship of the interfaces between BCC precipitate and FCC matrix have been clarified as the Kurdjumov-Sachs (KS) interfaces presenting [011]FCC //[111]BCC and (111)FCC // (011)BCC. The annealed Ni2FeCrW0.5 MEA exhibited outstanding strengthductility synergy, combining a high ultimate tensile strength of -982 MPa and an excellent ductility of -29%. Strengthening mechanisms were estimated and compared with experimental measurements, revealing that the coherent BCC/& mu; precipitates bring out effective precipitation strengthening.