Effect of alloy composition on morphology and volume fraction of quasi-crystalline of Mg-Zn-Y alloy

• Main Authors: YUAN Jiao-na, WANG Jian-li, YANG Zhong, GUO Yong-chun, LI Jian-ping
• Format: Article
• Language: zho
• Published: Journal of Materials Engineering 2019-03-01
• Series: Journal of Materials Engineering
• Subjects: Mg-Zn-Y alloy; quasi-crystalline I-phase; morphology; volume fraction; formation mech-anism of quasi-crystalline I-phase
• Online Access: http://jme.biam.ac.cn/CN/Y2019/V47/I3/116
• ISSN: 1001-4381; 1001-4381

Mg-Zn-Y alloys with a Zn/Y=6:1(atomic ratio) were prepared by steel mould casting method. The effect of alloy composition on phase constituents as well as the morphology, volume fraction of Mg₃Zn₆Y quasi-crystalline phase (quasi-crystalline I-phase) in Mg-Zn-Y alloys was investigated by XRD, SEM, EDS, TEM and DSC. Results show that the phase constituents, the morphology, volume fraction and formation mechanism of Mg₃Zn₆Y quasi-crystalline I-phase in the Mg-Zn-Y alloys are closely related to alloys' compositions. The formation reaction of quasi-crystalline I-phase is transferred from fully peritectic reaction to the combination of peritectic and eutectic reactions, and to completely eutectic reaction with the decrease of Zn and Y content in the alloys. When the Y content is and more than 7%(atom fraction), the alloys are composed of (Mg,Zn)₅Y, quasi-crystalline I-phase, Mg₂Zn₃ and Mg₇Zn₃ phases and they are distributed in a layered form in the alloy, and the quasi-crystalline I-phase takes the polygonal form by peritectic reaction during solidification. When the Y content is less than 7%, Mg phase precipitates in the alloys and their microstructure consists of (Mg,Zn)₅Y, quasi-crystalline I-phase, Mg₇Zn₃ and Mg phases. When the Y content is between 5% and 7%, the quasi-crystalline I-phase is precipitated by peritectic and eutectic reaction, and eutectic reaction, which dominates the precipitation of quasi-crystalline I-phase. When the Y content is and less than 4%, the quasi-crystalline I-phase forms totally a (Mg+I-phase) lamellar eutectic microstructure by eutectic reaction. The volume fraction of quasi-crystalline I-phase is all greater than 27%,and in Mg₃₀Zn₆₀Y₁₀ alloy is the maximum (about 77%) among the studied alloys.