ARTICLE IN PRESS H O S T E D BY Available online at www.sciencedirect.com ScienceDirect Journal of Magnesium and Alloys ■■ (2017) ■■–■■ www.elsevier.com/journals/journal-of-magnesium-and-alloys/2213-9567 Review Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner Tingting Tong, Fan Zhang, Shuhong Liu *, Yong Du, Kun Li State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China Received 12 November 2016; revised 17 February 2017; accepted 17 February 2017 Available online Abstract Phase equilibria of the Mg-Sn-Ag system in Mg-rich corner at 320 and 400 °C were experimentally investigated with nine ternary alloys subjected to electron probe microanalysis and X-ray diffraction techniques. No ternary compounds were observed at both isothermal sections. Two three-phase triangles, i.e. hcp (Mg) + Mg2Sn + Mg3Ag and Mg2Sn + Mg3Ag + MgAg (bcc_B2), were both observed at 320 and 400 °C. A new three-phase region of Ag3Sn + Mg2Sn + MgAg (bcc_B2) was additionally observed at 320 °C, which implied that the binary phase Ag3Sn has a considerable solubility of Mg in the ternary system at the temperature. And the maximal solubility of Mg in Ag3Sn was measured to be 27.2 at.%. This result is not consistent with the thermodynamic calculated isothermal section at 350 °C from Wang et al. [11] and put forward a new requirement or refinement for the optimization of the Mg-Sn-Ag ternary system. At 400 °C, the maximal solubility of Sn in the Mg3Ag phase was determined to be about 3.0 at.% Sn, and the solubility of Ag in Mg2Sn was negligible. The temperature of ternary eutectic reaction at Mg-rich corner (L↔hcp (Mg) + Mg54Ag17 + Mg2Sn) was measured by differential scanning calorimetry. The partial isothermal sections in Mg-rich corner of the ternary system at 320 and 400 °C were then constructed based on the above experimental data. © 2017 Production and hosting by Elsevier B.V. on behalf of Chongqing University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Keywords: Mg-Sn-Ag system; X-ray diffraction techniques; Electron probe microanalysis; Differential scanning calorimetry; Isotheromal sections 1. Introduction With their low density, excellent specific strength, good machinability, high thermal conductivity and recycle ability, Mg-based alloys have attracted more and more world-wide attention in recent decades [1] and a number of Mg alloys have been developed, such as Mg-Al based alloys, Mg-Zn based alloys and Mg-RE based alloys. However, the strength and creep resistance of Mg-based alloys are often significantly reduced with the increase of temperature, which can bring out the fact that the corrosion resistance, creep resistance and wear resistance of the alloys have difficulty meeting the requirements. Therefore, increasing the high temperature performance of the alloys is an important subject for magnesium alloy research in recent years. Mg-Sn-based alloys were proved to have good mechanical properties at high temperatures due to the existence of Mg2Sn, * Corresponding author. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China. Fax: +86 731 88710855. E-mail address: shhliu@csu.edu.cn (S. Liu). which has a high melting point [2]. They were thus considered as potential heat-resistant magnesium alloys. Unfortunately, the quenched Mg-Sn-based alloys take a long time to reach peak hardness, which is not practical for industrial production [3]. In addition, with the increase of Sn content, the Mg2Sn phase coarsens and the alloys form a semi-continuous network structure at the grain boundary. All above phenomena deteriorate the performance of the alloys [4]. It was reported that the addition of Ag can significantly refine the grain to improve the creep resistance and enhance the mechanical properties by aging strengthening [5–8]. For the advanced development of the Mg-Sn-Ag based alloys, knowledge on the phase equilibria of the Mg-Sn-Ag system becomes very important. Up to now, very limited experimental information is available about the ternary Mg-Sn-Ag system in the literature. Raynor et al. [9] firstly measured isothermal sections of the ternary system in Ag-rich corner at the 450 and 550 °C by the microscopic and X-ray diffraction (XRD) methods. Using thermal analysis, optical microscopy and XRD techniques, Karonik et al. [10] supplemented the phase region of Mg-rich corner at 450 °C and determined the vertical sections http://dx.doi.org/10.1016/j.jma.2017.02.003 2213-9567/© 2017 Production and hosting by Elsevier B.V. on behalf of Chongqing University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ 2 Table 1 Crystal structure data on the solid phases in the ternary Mg-Ag-Sn system. Phase Pearson symbol/prototype Lattice parameters (Å) Reference Ag3Mg MgAg(bcc_B2) AgMg4 cP4-AuCu3 cP2-CsCl hP* [16] [12] [14] AgMg3 Ag17Mg54 cF*-AsNa3 O/142 Mg2Sn hcp cF12-CaF2 hP2- Mg Ag3Sn oP8-Cu3Ti a = 4.111 a = 3.331 a = 2.509 c = 14.470 a = 17.622 a = 14.240 b = 14.209 c = 14.663 a = 6.765 a = 2.966 c = 4.782 a = 5.968 b = 4.780 c = 5.184 [14] [14] [13] [15] [15] at constant 10 wt. % Ag and 10 wt. % Sn. In recent years, Wang et al. [11] determined the phase relations at the Mg-rich corner at 350 and 415 °C by XRD and electron probe microanalysis (EPMA). The solubilities of Ag in Mg2Sn at 350 and 415 °C are both less than 0.1 at.%, the maximal solubility of Sn in Mg3Ag is as large as 3 ± 0.5 °C at.%. No solubilities of Mg in the Ag-Sn compounds were observed in the ternary system. The ternary vertical sections with compositions of 10 at.% Sn and 30 at.% Ag were also determined by differential scanning calorimetry (DSC) measurements. Based on the available experimental data, Wang et al. [11] optimized the Mg-Sn-Ag system and calculated the isothermal sections of 415 and 350 °C and the liquidus projection. However, there are very scarce experimental points below 400 °C, it limits the optimization and may lead to some wrong understandings about the phase relations. The Mg-Ag and Mg-Sn phase diagrams were critically evaluated by Nayeb–Hashemi and Clark [12,13]. According to the assessed Mg-Ag phase diagram, there are three intermediate compounds in the Mg-Ag system, viz. MgAg (bcc_B2), Ag3Mg, Mg3Ag. Later on, the phase equilibria of the Mg-Ag system were re-investigated by Lim et al. [14] using DSC, XRD and scanning electron microscope (SEM) techniques, and the existences of AgMg4 and Ag17Mg54 were confirmed. In the Mg-Sn system, there is only one compound viz. Mg2Sn. For the Ag-Sn system, there are two intermediate compounds, viz. hcp(Ag4Sn) and Ag3Sn reported by Mas [15]. Table 1 summarizes all the intermediate phases in the three binary systems of the Mg-Sn-Ag system. The aims of the present work are to determine the phase equilibria of Mg-Sn-Ag in Mg-rich corner and to provide more accurate experimental data for the future thermodynamic modeling of the ternary system. 2. Materials and methods Nine alloys were prepared with high-purity Mg (99.99wt.% purity), Ag (99.99wt.% purity) and Sn (99.99 wt.% purity). The accurately weighed Mg and Ag pieces and the Sn blocks were mixed in a graphite crucible, and then melted by a frequency induction furnace under a high-purity argon atmosphere. The melted alloys were cut into two blocks and sealed into quartz capsules for an equilibrium treatment. The blocks were wrapped by tantalum sheets to avoid the interaction of the samples with quartz capsules at annealed temperatures. The quartz capsules were put in the L4514-type diffusion furnaces at 320 ± 2 °C for 60 days and 400 ± 2 °C for 45 days, respectively. After annealing, all the alloys were quenched in cold water without breaking the quartz tubes. The annealed alloys were examined by XRD (D8-advance, Bruker, Germany) at 40 kV and 40 mA to identify the phases included in the alloys. The metallographic samples of the annealed alloys were firstly examined using optical microscopy and then analyzed by EPMA (JXA-8530, JEOL, Japan) employing pure Mg (99.99 wt.%), Sn (99.9 wt.%) and Ag (99.9 wt.%) as standard to determine the composition of each phase in the ternary system. The EPMA measurements were carried out at 15 kV and 2 × 10−8 A. To avoid a reaction with water, the metallographic samples were ground and polished under alcohol. Alloy # 9 (Mg85.0Ag5.0Sn10.0) annealed at 320 °C for 60 days was examined by DSC (DSC404C, Netzsch, Germany). The sample was sealed in a small Ta crucible due to the high evaporability of Mg. The measurement was conducted from room temperature to 800 °C with heating and cooling rates of 5 °C/min under an argon gas atmosphere. In the examined temperature range, the accuracy of the temperature measurement was estimated to be ±2 K by measuring the melting temperatures of some pure metals (In, Sn, Zn, Al, Ag, Au, Bi, Ni). The accurate temperature of the invariant reaction was determined from the onset of the thermal effects during the heating step. 3. Results and discussions The nominal compositions and the experimental information on the phase equilibria of the alloys annealed at 320 °C for 60 days and 400 °C for 45 days are summarized in Tables 2 and 3, respectively. Phases identification and the compositions of all the alloys were analyzed by XRD and EPMA. All the results of both measurements agreed well with each other. 3.1. Isothermal section at 400 °C The experimental investigation of the isothermal section at 400 °C mainly focused on the composition region from 50 at.% Mg to 100 at.% Mg. It is because of that that the other compositions are in single phase regions or contain liquid phase which could react with quartz capsules. XRD patterns and backscattered electron (BSE) images of the alloys annealed at 400 °C for 45 days are presented in Figs. 1 and 2, respectively. Figs. 1a and 2a are the XRD pattern and the BSE micrograph of the annealed alloy # 1 (Mg50.0Ag45.0Sn5.0), respectively. As shown in Fig. 2a, the gray phase is Mg2Sn and the light-gray phase is MgAg (bcc_B2). It reveals that the alloy is located in a two-phase region of Mg2Sn and MgAg (bcc_B2). Alloys # 2 (Mg50.0Ag30.0Sn20.0) and # 3 (Mg50.0Ag40.0Sn10.0) have the similar microstructure with the different volume ratio of Mg2Sn and MgAg (bcc_B2). The BSE microstructure and XRD pattern of the annealed alloy # 4 Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ 3 Table 2 Summary of the experimental information on the phase equilibria in the alloys annealed at 400 °C for 45 days (at.%). Nominal Composition Composition by EPMA No. Mg Ag 1 50.0 45.0 Sn 5.0 2 50.0 30.0 20.0 3 50.0 40.0 10.0 4 65.0 15.0 20.0 5 75.0 5.0 20.0 Phases Mg Ag Sn Remark Mg2Sn MgAg (bcc_B2) Mg2Sn MgAg (bcc_B2) Mg2Sn MgAg (bcc_B2) Mg3Ag Mg2Sn MgAg (bcc_B2) hcp(Mg) Mg2Sn Mg3Ag 66.9 46.0 67.1 38.2 66.6 49.0 73.5 66.8 56.2 97.4 67.8 77.0 1.0 49.5 0.5 52.5 2.2 49.1 23.5 0.2 43.5 1.6 0.1 20.6 32.1 4.5 32.5 9.3 31.2 2.0 3.0 32.9 0.3 1.0 32.1 2.3 Tie-line (Mg65.0Ag15.0Sn20.0) indicate that Mg2Sn, Mg3Ag and MgAg (bcc_B2) are in three-phase equilibrium, as shown in Figs. 1b and 2b. In the Fig. 2b, the black phase is Mg3Ag, the gray phase is Mg2Sn, and the lighter gray phase is MgAg (bcc_B2). In the three-phase region, both the solubilities of Ag in Mg2Sn and Sn in MgAg (bcc_B2) are negligible, but the solubility of Sn in Mg3Ag is up to be about 3 at.%. Experimental results of the annealed alloy # 5 (Mg75.0Ag5.0 Sn20.0) in Figs. 1c and 2c show that the alloy is composed of the dark hcp (Mg) phase, the light Mg2Sn phase and the gray Mg3Ag phase. This alloy is located in a three-phase field of hcp (Mg) + Mg2Sn + Mg3Ag. The solubilities of Ag and Sn in hcp (Mg) are about 1.6 at. % and 1.0 at. %, respectively. The solubility of Sn in Mg3Ag is about 2.3 at. %. However, the solubility of Ag in Mg2Sn is negligible. Taking into account the present experimental results, the isothermal section at 400 °C in Mg-rich corner is presented in Tie-line Tie-line Tie-triangle Tie-triangle Fig. 3, in which the nominal compositions of the alloys are also indicated. Two three-phase regions at the Mg-rich corner are determined at 400 °C, i.e. hcp (Mg) + Mg2Sn + Mg3Ag and Mg2Sn + Mg3Ag + MgAg (bcc_B2), which is consistent with the experimental and calculated results at 415 °C in literature [11]. 3.2. Isothermal section at 320 °C Figs. 4 and 5 are the XRD patterns and BSE images of a few representative alloys annealed at 320 °C for 60 days, respectively. Figs. 4a and 5a are the XRD pattern and BSE image of annealed alloy # 2 (Mg50.0Ag30.0 Sn20.0), which indicate that the alloy is located in a two-phase region of Mg2Sn + MgAg (bcc_B2). Besides, the alloy # 1 (Mg50.0Ag45.0Sn5.0) has the similar microstructure with the different volume ratio of Mg2Sn and MgAg (bcc_B2). Because of the small amount of the Table 3 Summary of the experimental information on the phase equilibria in the alloys annealed at 320 °C for 60 days (at.%). Nominal Composition Composition by EPMA No. Mg Ag Sn 1 50.0 45.0 5.0 2 50.0 30.0 20.0 4 65.0 15.0 20.0 5 75.0 5.0 20.0 6 35.0 45.0 20.0 7 65.0 25.0 10.0 8 77.5 17.5 5.0 9 85.0 5.0 10.0 Phases Mg Ag Sn Mg2Sn MgAg (bcc_B2) Mg2Sn MgAg (bcc_B2) Mg3Ag Mg2Sn MgAg (bcc_B2) hcp(Mg) Mg2Sn Mg3Ag Ag3Sn Mg2Sn MgAg (bcc_B2) Mg3Ag Mg2Sn MgAg (bcc_B2) hcp(Mg) Mg2Sn Mg3Ag hcp(Mg) Mg2Sn Mg3Ag —— 49.5 67.2 38.0 74.1 68.4 54.0 97.6 67.3 77.9 27.2 67.4 35.0 73.8 67.3 56.8 97.1 68.2 77.2 97.7 68.6 78.6 —— 48.7 0.5 52.9 23.0 0.2 45.7 1.3 0.1 19.8 54.8 0.4 52.4 23.4 1.4 45.2 2.5 0.2 20.7 0.8 1.4 19.3 —— 1.8 32.3 9.2 2.9 31.5 0.3 1.1 32.6 2.3 18.1 32.2 12.7 2.8 31.3 0.2 0.4 31.6 2.2 1.5 30.1 2.2 Remark Tie-line Tie-triangle Tie–triangle Tie-triangle Tie-triangle Tie–triangle Tie–triangle Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS 4 T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ Fig. 1. XRD patterns of the representative alloys annealed at 400 °C for 45 days: (a) alloy 1 (Mg50.0Ag45.0Sn5.0), (b) alloy 4 (Mg65.0Ag15.0Sn20.0), (c) alloy 5 (Mg75.0Ag5.0Sn20.0). Fig. 2. BSE images of representative alloys annealed at 400 °C for 45 days: (a) alloy 1 (Mg50.0Ag45.0Sn5.0), (b) alloy 4 (Mg65.0Ag15.0Sn20.0), (c) alloy 5 (Mg75.0Ag5.0Sn20.0). Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ Fig. 3. Experimental isothermal section at 400 °C of the Mg-Sn-Ag system in Mg-rich corner with the nominal compositions. 5 Mg2Sn in the alloy # 1 (Mg50.0Ag45.0Sn5.0) at 320 °C, the measurement of EPMA was not determined. The compositions of phases MgAg (bcc_B2) and Mg2Sn determined by EPMA are presented in Fig. 6, which exhibit that the solubility of Sn in MgAg (bcc_B2) changes along with the compositions of alloys and the solubility of Ag in Mg2Sn can be negligible. The annealed alloy # 6 (Mg35.0Ag45.0Sn20.0) is located in a three-phase equilibrium region of Ag3Sn + Mg2Sn + MgAg (bcc_B2), as shown in Fig. 4b. The microstructure of the alloy is shown in Fig. 5b, in which the black and gray phases are Mg2Sn and MgAg (bcc_B2), respectively, the lighter gray phase is Ag3Sn. The phase boundary of the three-phase region (Ag3Sn + Mg2Sn + MgAg (bcc_B2)) is accurately established based on the EPMA measurement. And the solubility of Mg in Ag3Sn was measured to be 27.2 at. %. Fig. 4. XRD patterns of the alloys annealed at 320 °C for 60 days: (a) alloy 2 (Mg50.0Ag30.0Sn20.0), (b) alloy 6 (Mg35.0Ag45.0Sn20.0), (c) alloy 7 (Mg65.0Ag25.0Sn10.0), (d) alloy 8 (Mg77.5Ag17.5Sn5.0). Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS 6 T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ Fig. 5. BSE images of representative alloys annealed at 320 °C for 60 days: (a) alloy 2 (Mg50.0Ag30.0Sn20.0), (b)alloy 6 (Mg35.0Ag45.0Sn20.0), (c) alloy 7 (Mg65.0Ag25.0Sn10.0), (d) alloy 8 (Mg77.5Ag17.5Sn5.0). It should be noted that the experimental results observed in the annealed alloy # 6 (Mg35.0Ag45.0Sn20.0) are not consistent with the work of Wang et al. [11], in which the thermodynamically extrapolated three-phase region is Mg2Sn + hcp (Ag4Sn) + MgAg Fig. 6. (Online color) Experimental isothermal section at 320 °C of the Mg-Sn-Ag system in Mg-rich corner with the nominal compositions. (bcc_B2), and there is not a phase region including Ag3Sn and MgAg (bcc_B2) simultaneously. Besides, thermodynamic extrapolation is based on limited experimental information, we think our present experimental results are confidential. The differences indicate that the experimental information about the Mg-Sn-Ag ternary system is not comprehensive to optimize. The annealed alloy # 7 (Mg65.0Ag25.0Sn10.0) is characterized to be in the three-phase region of Mg2Sn + Mg3Ag + MgAg (bcc_B2), as shown in Figs. 4c and 5c. As presented in Fig. 5c, three phases can be seen, i.e. the dark Mg3Ag phase, the gray Mg2Sn phase and the light-gray MgAg (bcc_B2) phase. The XRD pattern and BSE image of the annealed alloy # 8 (Mg77.5Ag17.5Sn5.0) are presented in Figs. 4d and 5d, respectively. In Fig. 5d, the black phase is hcp (Mg), the gray phase is Mg3Ag and the light-gray phase is Mg2Sn. The experimental results indicate the alloy is located in the three-phase equilibrium field of Mg2Sn + Mg3Ag +hcp (Mg). Based on the present experimental results and the binary phase diagrams reported in literature [12–16], the isothermal section of Mg-rich corner at 320 °C is constructed and Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003 ARTICLE IN PRESS T. Tong et al. / Journal of Magnesium and Alloys ■■ (2017) ■■–■■ 7 reasonable. All the reaction temperatures are consistent with the experimental results (463, 529 and 569 °C respectively) from Wang et al. [11]. 4. Conclusions Fig. 7. DSC curves of the representative alloy 9 (Mg85.0Ag5.0Sn10.0). exhibited in Fig. 6. The measured tie-lines and tie-triangles along with the locations of the prepared alloys are displayed in the figure. According to our present work, Ag3Sn is in equilibrium with Mg2Sn and MgAg (bcc_B2) at 320 °C and the solubility of Mg in Ag3Sn is 27.2 at. %, which are not consistent with the work of Wang et al. [11]. All the results indicate that it is necessary for the optimization of Wang et al. [11] to do some refinement in order to reproduce the experimental information. No ternary compounds were observed. 3.3. DSC measurements The DSC curves of alloy # 9 (Mg85.0Ag5.0Sn10.0) annealed at 320 °C for 60 days are presented in Fig .7. There are two distinct endothermic peaks in the heating process, referred to the vertical section at constant 10 at. % Sn from Wang et al. [11], the first peak represents the ternary eutectic reaction L↔hcp (Mg) + Mg54Ag17 + Mg2Sn, and the second peak indicates a monovariant transition of binary eutectic reaction L↔hcp (Mg) + Mg2Sn. Three exothermic peaks are presented during the cooling curve. The first two peaks are well repeated the peaks during heating process, and the third peak represents the transition of L↔Mg2Sn. The reason for the difference between the cooling curve and heating curve is that the peak of the reaction L↔Mg2Sn is weak during the heating process. In conclusion, the ternary eutectic equilibrium temperature of L↔hcp (Mg) + Mg54Ag17 + Mg2Sn was determined to be 470 °C and the transition reaction temperatures of L↔hcp (Mg) + Mg2Sn and L↔Mg2Sn were measured to be 534 °C and 566 °C, respectively. Compared to the temperature of eutectic reaction: L↔hcp (Mg) + Mg2Sn, in the Mg-Sn binary system (561 °C) from Nayeb–Hashemi and Clark [13], the result is Based on XRD, EPMA and DSC measurements, phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner were analyzed, the isothermal sections in Mg-rich corner at 320 and 400 °C were constructed, and no ternary compounds were obtained. The three-phase regions of Mg2Sn + Mg3Ag + MgAg (bcc_B2) and Mg2Sn + Mg3Ag + hcp (Mg), and the two-phase fields of Mg2Sn + MgAg (bcc_B2) and Mg2Sn + Mg3Ag were observed at both isothermal sections. Three-phase equilibrium of Ag3Sn + Mg2Sn + MgAg (bcc_B2) was observed at 320 °C but not 400 °C. At 320 °C, the solubility of Mg in Ag3Sn was measured to be 27.2 at. %. The results put forward a new requirement for the optimization of the Mg-Sn-Ag ternary system. The temperature of the invariant reaction (L↔hcp (Mg) + Mg54Ag17 + Mg2Sn) in Mg-rich corner was determined to be 470 °C. Acknowledgments The financial support from National Key Research and Development Plan (No. 2016YFB0701202) and State Key Laboratory of Powder Metallurgy Central South University, China (No. 1991DA105636), are greatly acknowledged. References [1] B.L. Mordike, T. Ebert, Mater. Sci. Eng. 302 (2001) 37–45. [2] T.B. Massalski, Binary Alloy Diagram, ASM International, Geauga County, OH, 1990. [3] K. Van der Planken, J. 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Massalski (Ed.), Binary Alloy Phase Diagrams, second ed., ASM in International, Metals Park, Ohio, 1990. [16] L.M. Clarebrough, M.B. Bever, Trains. Met. Soc. AIME 230 (1964) 284. Please cite this article in press as: Tingting Tong, Fan Zhang, Shuhong Liu, Yong Du, Kun Li, Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner, Journal of Magnesium and Alloys (2017), doi: 10.1016/j.jma.2017.02.003