Microstructural evolution and mechanical properties of accumulative back extruded duplex (α + β) brass

The microstructural evolution and mechanical performance of α + β brass alloy (Cu-40%Zn) processed through the accumulative back extrusion (ABE) were investigated in this study. The detailed microstructural evolution during the ABE process exhibited a significant difference in deformation mechanisms operating within each phase, consequently altering their grain refinement mechanism. The rotation of the mechanical twinning along the shear bands contributed to the strain accommodation in the α-phase, while the subgrain formation and rotation within the shear bands resulted into a significant α-phase grain refinement at higher ABE passes. On the other hand, the β-phase, which was strain hardened at the early stages of straining, at higher ABE passes, was fragmented into refined subgrains by the highly strained α/β interphase boundaries. The formation of the newly recrystallized grains with ~0.24 μm (α-phase) and ~1.21 μm (β-phases) sizes, mechanical twin boundaries, shear bands and strain incompatibility zones contributed to a significant increase in the ultimate strength from ~350 MPa for the as-received sample to ~800 MPa in the three-pass ABE processed sample.