Effect of strain rate on twinning in a Zr alloy

Zr–1Nb alloy uniaxially compressed at room temperature at 10−2 and 103 s−1 exhibited twinning and a three-stage strain-hardening behavior. At 103 s−1 the twin fraction initially increased to 0.3, decreasing to 0.02 at higher strains. Despite the difference in texture at intermediate strains, the final texture was similar at both strain rates. The increasing strain-hardening rate in the second stage was attributed to strengthening from grain boundaries and dislocations, and softening from reorientation due to twinning.