Effects of precipitate type on twin/slip activity in ZK60 alloys and yield asymmetry

The strengthening effects of different precipitates in ZK60 alloys on prismatic slip and {10–12} extension twinning (ET) were studied by experimental work and Visco-Plastic Self Consistent (VPSC) modeling. The results showed that the critical resolved shear stress (CRSS) of ET and prismatic slip are increased by 21 MPa and 9 MPa, respectively after aged for 10 h. The CRSS of ET was only slightly increased by 2 MPa after aged for 30 h; while it was increased by 32 MPa for prismatic slip. Yield asymmetry was sensitive to the variation of CRSS for these two deformation modes. These results are consistent with recent calculations by an Orowan hardening model. Moreover, it was found that disk-like β′2 precipitates have little influence on the total volume fraction of twins activated during compression along the rolling direction, while the precipitation of rod-like β′1 tends to reduce the twin volume fraction.