Overcoming strength-ductility trade-off via L21 precipitate-strengthening in Al0.3CoCrNiTi0.1 high entropy alloy at room and cryogenic temperatures

We developed a novel Al 0.3 CoCrNiTi 0.1 high entropy alloy (HEA) comprising of face-centered-cubic (FCC) matrix and the L2 1 -Ni 2 TiAl precipitates. This alloy exhibits exceptional strength-ductility combinations at both room and cryogenic temperatures. The mechanical properties of this alloy increased when the temperature decreased. For instance, the yield strength, tensile strength and ductility at room temperature were estimated to 556, 1134 MPa and 38 %, while those at cryogenic temperature were measured to 682, 1422 MPa and 36 %, respectively. Theoretical calculation of strengthening mechanisms indicated that the strengthening was mainly dominated by L2 1 precipitates. Detailed investigation of deformation mechanisms through electron back-scattered diffraction (EBSD) and transmission electron microscope (TEM) revealed that the enhanced strain-hardening rate at cryogenic temperatures was associated with the L2 1 precipitates, the reduced SF spacing and SF networks. These findings suggest that the Al 0.3 CoCrNiTi 0.1 HEA could provide a promising candidate for advanced cryogenic structural applications.