China Foundry
Title: Microstructure evolution and age-hardening response in Mg-Sn-Sm alloys under a wide range of Sm/Sn ratio
Author: *Feng Liu1,2, **Wen-xin Hu1,2, Zheng-hua Yang1,2, Wei Wang2, and Wei He2
Address: 1. State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou 014030, Inner Mongolia, China; 2. Baotou Research Institute of Rare Earths, Baotou 014030, China
Key words: magnesium alloy; as-cast; microstructure evolution; age-hardening; precipitates; Sm/Sn ratio
CLC Nmuber: TG146.21
Document Code: A
Article ID: 1672-6421(2022)03-405-07
Abstract:
The microstructure evolution and age-hardening response for different Sm/Sn ratios (0-2.55 in wt.%) of Mg-Sn-Sm alloys were investigated. The second phase formation in as-cast alloys and the precipitates in peak-aged alloys were characterized using XRD, FESEM and HAADF-STEM with EDS techniques. Results indicate that the Sm/Sn ratio has a great influence on the phase constitution, α-Mg grain size and age-hardening response. With the increment of Sm/Sn ratio, Mg41Sm5 and thermally stable MgSnSm phases precipitate. Whenthe Sm/Sn ratio is about 1.19, the secondary dendrite arm spacing of α-Mg grains decreases significantly. Furthermore, the alloy with Sm/Sn ratio up to 2.55 exhibits the highest age-hardening response, the hardness value increases from 52 HB at solution-treated condition to 74 HB at peak-aged condition by ageing at 220 °C for a short ageing time of 4 h. This is attributed to the large volume fraction of needle-like Mg3Sm precipitates formed in the α-Mg matrix during ageing treatment, which results in a significant precipitation strengthening effect.