The Effect of Strain Reversal during High Pressure Torsion on the
Evolution of Microstructure and Hardness in Al-2.5wt% Mg alloy
Abstract
The present work aims to investigate the effect of strain reversal
during High Pressure Torsion (HPT) on the evolution of microstructure
and hardness properties of Aluminium-Magnesium (Al-2.5%Mg) alloy. For
this purpose, Al-2.5%Mg alloy was subjected to monotonically (CW) and
strain reversal (CW-CCW) deformation by High Pressure Torsion (HPT). The
samples were subjected to a series of rotations in monotonically and
strain reversal deformation with same equivalent strains of 1, 4, 12, 24
and 60 under an applied load of 6 GPa and with 1 rpm under
quasi-constrained conditions. It was observed that Al-2.5%Mg when
subjected to different routes, follows same trend in the evolution of
the ultrafine structure, i.e. initial recrystallized microstructure with
large grain size throughout the disk, at low strain level sub grains
with prominent LAGBs network inside the grains and ultimately at the
higher strains ultrafine microstructure throughout the disk
characterized by equiaxed grains separated by HAGBs. The only exception
to this was observed in case of Al-2.5%Mg during high strains at the
centre regions where the fraction of HAGBs was found strikingly less as
compared to its counterpart during strain reversal deformation. Hardness
homogeneity was not observed for Al-2.5%Mg where the hardness at the
centre regions was observed to be lesser than the edge regions with
exceptionally less hardness at centre for strain reversal specimens at
higher strains.