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.

Double-hit hot compression tests were carried on medium-carbon low-alloy steels using Gleeble 3800® thermomechanical simulator. The tests were performed at strain rates of 0.25 and 0.5 s-1 and temperatures of 1150 and 1200 °C with an interpass time of 5s. The onset of critical stress for dynamic transformation (DT) were detected using the double‐differentiation method. This metallurgical phenomenon was initiated under all testing conditions. The results show that the critical stress for DT increases with decrease in temperature and increase in strain rate.