Large-strain softening of aluminum in shear at elevated temperature

Abstract: Pure aluminum deformed in pure shear at elevated temperature reaches a broad “peak” stress and then undergoes about a 17 pct decrease in flow stress with deformation with, roughly, 1 to 2 equivalent uniaxial strain. Beyond this strain, the flow stress is approximately constant. The sources for this softening are unclear. The suggested basis includes texture softening, microstructural softening, enhanced dynamic recovery, and discontinuous dynamic recrystallization. Experiments were performed in which specimens were deformed in torsion to various strains within the softening regime followed by compression tests at ambient and elevated temperature. Analysis of the compressive yield strengths indicate that the softening is most likely substantially explained by a decrease in the average Taylor factor.