Processing, microstructure evolution and mechanical property improvements of an Al-V-Cr-Mn-Fe-Ni CCA with an as-cast BCC/B2 coherent nanostructure

This article reports a thermo-mechanical processing method that enables microstructure tailoring and mechanical property improvement in an Al-V-Cr-Mn-Fe-Ni complex concentrated alloy (CCA) with an as-cast microstructure consisting of coherent B2 precipitation in a BCC matrix. A large increment (45%) in tensile strength has been achieved after the non-uniform as-cast microstructure was changed to a uniform, recrystallized structure after processing. Microstructure evolution and the corresponding mechanical properties were also studied for this alloy. It was found by selecting the proper temperature at the final annealing step, significant improvements in ductility can be further achieved without compromising the high strength; the mechanical behavior of this alloy can be effectively tuned by varying the final annealing temperature. Furthermore, to validate efficacy and generalizability of the developed thermo-mechanical processing method on CCAs with the same type of microstructure, but in a different compositional space, the same method was applied to an Al-Cr-Fe-Co-Ni CCA composition found in the literature. Similar to our Al-V-Cr-Mn-Fe-Ni CCA, tensile test of the processed Al-Cr-Fe-Co-Ni CCA revealed vast improvement in tensile strength (over 200 MPa) without sacrificing any ductility.

Automated summary

By studying a thermo-mechanical processing method, the non-uniform as-cast microstructure was successfully transformed into a uniform recrystallized structure, leading to a significant improvement in the tensile strength of the alloy. Furthermore, by selecting the appropriate annealing temperature, significant improvements in ductility can also be achieved without compromising the high strength.