Abstract:The influence of free-end torsion on compressive behavior of an extruded AZ31 rod at various temperatures was studied. Pre-torsion generates a high density of dislocations and a large number of twins in the matrix, which can largely enhance the compressive yield strength at RT and 100 °C. However, with increasing temperature, hardening effect via pre-torsion gradually decreases. When the compressive temperature reaches 300 °C, pre-torsion reduces the compressive yield strength. Moreover, initial dislocations and twins via torsion help to refine the sub-structure and accelerate the continuous dynamic recrystallization during compression at 200 °C. Thus, twisted sample exhibits more rapid flow softening behavior than the as-extruded sample at 200 °C. When compressed at 300 °C, the twins and dislocations via torsion were largely eliminated during the holding time, and the discontinuous dynamic recrystallization was enhanced. It is found that the compression curves of twisted sample and as-extruded sample tended to be coincident at 300 °C. Related mechanisms were discussed in detail.

Key words: Mg alloys; free-end torsion; compressive behavior; dynamic recrystallization; hot deformation; twins; dislocations