An EBSD analysis of heterogeneous microstructure and texture evolution in Al-5Cu powder consolidated by high-pressure torsion.

Abstract

The microstructure, texture and mechanical response of Al-5Cu (wt.%) powder consolidated by high-pressure torsion (HPT) were investigated as a function of strain and measurement position within bulk samples using electron backscatter diffraction (EBSD), scanning transmission electron microscopy (STEM) and Vickers microhardness. After 0.5 turn, the disc centre exhibited a fragmented, banded microstructure (grain size ~1.17 µm, ~33% high-angle grain boundaries HAGBs) with a weak Goss component and gradual development of shear-type texture. At the mid-radius, a heterogeneous duplex microstructure formed, with equiaxed grains (~1.72 µm, ~79% HAGBs) dominated by Goss and C shear components, and finer elongated grains (~0.93 µm, ~78% HAGBs) exhibiting deviated shear texture, reflecting localized strain differences. After 50 turns, the centre showed equiaxed grains (~0.72 µm, ~71% HAGBs) with heterogeneous texture including locally deviated shear components whereas the edge reached extreme refinement (~0.21 µm, ~80% HAGBs) with Goss and shear components slightly deviated from ideal positions suggesting incomplete homogenization even at high strain. Inspection by STEM revealed vortex-like flow, multiscale nanolamellar regions, supersaturated Al-Cu solid solutions and intermetallic Al2Cu/Al4Cu9 phases. The Vickers microhardness, with an initial value of ~50 Hv, increased from ~50–100 Hv after 0.5 turn to ~250–300 Hv after 50 turns across the disc. This overall hardening was associated with strain accumulation during HPT which is inherently heterogeneous due to the radial strain gradient. Overall, HPT consolidation produces a strain-dependent and heterogeneous microstructure where differential strain and incomplete homogenization govern texture evolution and mechanical properties.