Microstructure development and hardening during high pressure torsion of commercially pure aluminium: Strain reversal experiments and a dislocation based model

▶ Experiments show large softening on reverse straining in HPT of Al-1050. ▶ New model for hardening by HPT incorporating dislocation hardening by GNDs and SSDs. ▶ Model satisfactorily explains both hardening and softening during m-HPT and c-HPT. ▶ Hardening is predominantly due to dislocation hardening. ▶ Softening on reverse straining is predominantly due to reduction in GND density.