Comparative Analysis of Plastic Flow and Grain Refinement in Pure Aluminium Subjected to Simple Shear-Based Severe Plastic Deformation Processing

In the present work, effects of loading scheme and strain reversal on structure and hardness evolution have been studied by using high pressure torsion (HPT) and twist extrusion (TE) techniques. High purity aluminium (99.99%) was processed at room temperature up to a maximum total equivalent strain of ε[max] ≈ 8 by TE, and HPT in monotonic and reversal deformation modes with strain increment Δε[max] = 1. Minimum subgrain sizes reached in this study were 1.6 µm for TE and 1.1 µm for HPT. It was revealed that microstructural change with straining was a common consequence of severe plastic deformation (SPD) processing and was not affected significantly by the loading scheme. Among the SPD methods used in this study, HPT in monotonic regime produced the smallest grain size, while the most homogeneous microstructure was obtained by TE due to specific vortex-like flow field imposed by the tool geometry