Tune a highly ductile AlCrFe2Ni4 alloy by Ti addition for desired high mechanical strength

One of advantages of multi-element high-entropy alloys (HEAs) is their flexibility for microstructure manipulation, not only for the distribution of various phases but also the phase compositions, which greatly facilitate obtaining optimal combinations of high strength and high ductility with desired balance. In this study, we tailored a highly ductile AlCrFe2Ni4 alloy using Ti addition, which redistributed and induced various phases, including disordered and ordered FCC phases, large-lattice intermetallic L21 phase, nanoscale BCC precipitates, and minor η-Ni3Ti phase and MgZn2-type Fe2Ti Laves phase, etc. With increasing the Ti addition, the high-entropy alloy, AlCrFe2Ni4Tix (x = 0, 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5, in molar ratio), had its compressive yield strength considerably increased from 451.4 MPa up to 2105.5 MPa at expense of the fracture strain. The microstructure evolution and phase constituents in the AlCrFe2Ni4Tix with the Ti variation in a relatively wide range were characterized in detail and correlated with corresponding changes in mechanical properties of this high-entropy alloy system for further development and effective applications.