摘要
Mg alloys containing high Gd are featured by the outstanding aging hardening response. Here we conduct a systematic study on the hardening behavior and precipitation evolution in a Mg-10Gd alloy during isothermal aging at 200-250 degrees C by atomic-resolution high-angle annular dark-field scanning transmission electron micro-scopy (HAADF-STEM). The optimum aging temperature of Mg-10Gd is 200 degrees C with peak hardness of 102.4 HV. Hardness improvement of the aged samples at 200 degrees C mainly originates from precipitation strengthening, and beta' nano-precipitates with fine size of 10 nm are the main strengthening phases. The samples exhibit a certain aging hardening effect at 225 degrees C with peak hardness of 89.4 HV, due to the gourd-shaped beta' precipitates with coarse size of 100 nm. Furthermore, various metastable nanoscale structures (including short-range ordered GP zones, beta", beta T, beta M and beta F ' phases) are observed in the aged samples, and their formation mechanisms are rationalized in detail.
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单位南昌航空大学; 南京理工大学