High temperature strengthening mechanism of pure Zn with trace Mn addition

This work reveals how trace Mn significantly improves high temperature strength of pure Zn. The peak stress of pure Zn increases from 46 MPa to 84 MPa at 300 °C/0.1 s−1 after 0.8 wt.% Mn addition. The as-compressed Zn-0.8Mn alloy has a bimodal grain structure with fine grains surrounding a coarse grain. Transmission electron microscopy results show that Mn addition promotes activation of non-basal slip and pile-up of dislocations near coarse/fine grain boundary or MnZn13/Zn interface or on the MnZn13 particles. First-principles calculations indicate that Mn addition can reduce stacking fault energy values of basal and prismatic slip systems of Zn, therefore activating slip. Piled dislocations generate forward and back stresses, resulting in hetero-deformation induced strengthening. It serves as a suggestion for designing bimodal grain structures to improve strength of Zn alloys.