| Summary: | 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 <c+a> 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 <c+a> 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.
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