Aging hardening and precipitation evolution of Mg-Sc alloy with Zn alloying

[Display omitted] •Both α-phase and ScZn precipitate from the matrix during the aging process.•The Mg-Sc-Zn alloy aged at 300 °C has the highest hardness of 196.9 ± 6.9HV.•The nanosized α-phase and the needle-like ScZn precipitates are the main reasons for the Mg-Sc-Zn alloy aging hardening. The precipitation evolution and aging hardening effect of Zn alloying on the Mg-Sc alloy were analyzed in this study. Needle-like nanosized ScZn precipitates from the matrix at low-temperature aging, bulk-like ScZn precipitation gradually forms at high temperatures above 600 °C. Moreover, the α-phase also precipitates from the matrix during aging. The initial hardness of the solid solution β-phase alloy was almost 126.7 ± 3.2HV, the hardness of the alloy increases first and then decreases with the increase of the aging temperature from 200 °C to 600 °C. The alloy aged at 300 °C owns the highest hardness of 196.9 ± 6.9HV, further TEM reveals that the coherent nanosized α-phase precipitate with the Burgers orientation relations of β-phase and the needle-like ScZn precipitates are the main factors for the aging hardening of this Mg-Sc-Zn alloy after aging at 300 °C. These findings may provide the scientific basis for the alloying design of high-performance Mg-Sc alloys.