Evolution of microstructure and crystallographic texture in α-β Brass during equal channel angular pressing

Abstract

Two-phase α-β Brass was severe plastically deformed by equal channel angular pressing using route A up to four passes at 330 °C. The microstructure and crystallographic texture evolution were investigated for the α-FCC and β-Ordered B2 phase individually to understand their underlying deformation mechanism. Microstructural analysis reveals a decrease in the average grain size in both α- and β- phases from ~7 μm to ~1.5 μm, where most of the grain refinement took place up to 2nd pass. In α-phase, 111112¯ type twins evolve during deformation that reduces the strain in the α-grains with successive passes. This also leads to the formation of ∑3 coincident site lattice boundaries. In β-phase, dislocation slip occurred, and grains get elongated along the shear direction. β-grains come together to develop small bands about ~15° to the extrusion direction (ED). These small β-bands are interconnected to form larger β-bands parallel to ED. In α-phase, weak texture components evolve at positions deviated from the ideal end orientations due to the presence of secondary β-phase and twinning due to the low stacking fault energy of the α-phase. In β-phase, characteristic ECAP texture components evolve and strengthen with consecutive passes. This is attributed to the formation of the β-banded structure.