High temperature phase stabilized microstructure in Mg–Zn–Sn alloys with Y and Sb additions

Isothermal sections of the Mg-rich corner in the Mg–Sn–Y ternary system at 300 and 400°C

“…The equilibrium composition of the each phase was obtained at 300 and 400 • C by SEM-EDS, respectively. The composition of the light phase is 65.6 at.% Mg-34.4 at.% Sn, and that of the gray phase is 31.9 at.% Mg-32.3 at.% Sn-35.8 at.% Y at 300 • C. Unfortunately, the size of the dark phase is too small to measure accurately at 300 • C. The composition of the dark phase is 99.1 at.% Mg-0.9 at.% Sn, that of the light phase is of 66.9 at.% Mg-33.1 at.% Sn and that of the gray phase 31.9 at.% Mg-32.0 at.% Sn-36.1 at.% Y at 400 • C. The molar ratio of Mg:Sn:Y is roughly 1:1:1 for the gray phase in the Mg 70 Sn 20 Y 10 alloy heat treated at 300 and 400 • C, which was denoted as the MgSnY phase, as reported by Grony et al [12] and Rashkova and Keckes [15]. In the X-ray diffraction pattern of the Mg 70 Sn 20 Y 10 alloy, the ␣-Mg and Mg 2 Sn phases were marked and the residual peaks were indexed as the MgSnY phase (Fig.…”

“…Recently, the Mg-Sn-based alloys have been extensively studied as one of the potential creep resistant Mg alloys. The results obtained by Liu et al [8] showed that the creep resistance of Mg-(7-10) wt.% Sn alloys was equivalent to or even more than that of the AE42 alloy at 150 • C. This has been attributed to the presence of the Mg 2 Sn phase, which is more stable thermally than that of the Mg 17 Al 12 phase [9][10][11] More recently, the Mg-Sn-Zn-Y quaternary alloys were found to exhibit good comprehensive mechanical properties in wider temperature range due to the presence of several stable intermetallic compounds, such as MgSnY, MgZn 2 and Mg 2 Sn [12]. The phase equilibria and thermodynamic assessment of the Mg-Zn-Y and Mg-Sn-Zn systems have been well investigated [13,14].…”

Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

“…This situation is possibly related to the formation of MgCaSn phase in the 2 # alloy. Since the decomposition temperature of CaMgSn phase, 560°C [6], is higher than the solutionized temperature of this work, the Sn consumed by this phase will not be dissolved into the α-Mg matrix during solid solution treatment at the solutionized temperature of this work. As a result, the amount of Mg 2 Sn precipitated during the following aging of the 2 # alloy is theoretically lower than that of 1 # alloy.…”

“…At present, efforts are being made towards developing new creep-resistant magnesium alloys based on Mg-Zn-Sn system due to the following reasons [3]: (1) Zn can enhance the age hardening response and improve the castability, and has several stable intermetallics with Mg; (2) Sn not only can improve corrosion resistance but also can form a stable Mg 2 Sn compound with Mg. From recent investigations [4][5] the Mg-5Zn-5Sn alloy has been identified as one of the most promising magnesium alloys. According to the reported investigation results [6][7], the strengthening mechanism of Mg-5Sn-5Zn alloy is mainly related with the formation of two types of precipitates MgZn and Mg 2 Sn. However, it is further reported that the relatively poor structural stability of the alloy at high temperatures results in poor creep properties thus restricting the utilization of the alloy.…”

“…However, up to now, the investigations about the effects of alloying and microalloying on the microstructure and creep properties of Mg-5Zn-5Sn alloy are very rare. Although Gorny et al [6] reported that yttrium addition can improve the structural stability of the Mg-5Zn-5Sn alloy due to the formation of high temperature ternary phase MgSnY, the corresponding creep properties is not mentioned. In addition, due to the relatively expensive yttrium, the application of Y-containing Mg-5Zn-5Sn alloy is limited.…”