Al_xCoCrFeNi (0.5 < x < 3) high-entropy alloys: from cost-effective synthesis to strengthening via thermomechanical processing

In this study, the cost-effective synthesis, shaping and strengthening through hot and cold rolling of AlxCoCrFeNi (0.5 < x < 3) high-entropy alloys was investigated using an integrated processing method for the first time in the literature that involved non-centrifugal self-propagating high-temperature synthesis (SHS) followed by suction-casting. Compositions of the master alloys were well-controlled by virtue of thermochemical simulations (CALPHAD) and were acceptable for secondary processes. The FCC-based Al0.5CoCrFeNi alloy exhibited the highest hot deformability (36%) at 1000 degrees C among the all alloys resulting in a 109% increase in hardness, with respect to its as-cast state. It was possible to obtain Al0.5CoCrFeNi plates with improved hardness (42%) compared to the SHS master alloy, with substantial area reduction (131%) through the cold-rolling route. Despite the calculated phase diagram suggesting no sigma formation around 1000 degrees C, the hardness increase in the hot rolling process caused by the synergistic precipitation of BCC-B2 and s phases via hot deformation. It was concluded that the FCC-based Al0.5CoCrFeNi alloy can be successfully manufactured from oxides to final or semifinal products for applications requiring various thicknesses and improved mechanical properties through static or dynamic precipitation hardening by the selection of cold and hot rolling routes, respectively.