Effect of Zn and Ca Addition on Microstructure and Strength at Room Temperature of As-Cast and As-Extruded Mg-Sn Alloys.

Xiaoping Li,Yalin Lu,Xiaoyang Chen,Yang Zhang,Leipeng Song

doi:10.3390/ma11091490

Abstract

In this study, the effect of Zn and Ca addition on microstructure and strength at room temperature of Mg-Sn alloys was investigated by comparison of Mg-6Sn, Mg-6Sn-2Zn, and Mg-6Sn-2Zn-1Ca alloys in as-cast and as-extruded states. In the as-cast samples, α-Mg and Mg2Sn phases were the main phases of Mg-6Sn and Mg-6Sn-2Zn alloys, while the CaMgSn phase was formed in Mg-6Sn-2Zn-1Ca alloy due to the addition of the Ca element. Mg2Sn phase dissolved into the matrix during homogenization while CaMgSn phase remained. Incomplete dynamic recrystallization (DRX) took place in these alloys during hot extrusion. Fine Mg2Sn precipitates were observed in α-Mg matrix of as-extruded samples. Zn showed little influence on microstructure, whereas Ca reduced the volume fraction of un-DRXed grains and increased the size of DRXed grains. As-extruded Mg-Sn alloys exhibited typical fiber texture. The strength at room temperature of Mg-Sn alloys improved significantly after hot extrusion. The addition of Zn element was beneficial to the strength at room temperature of the Mg-6Sn alloy, while the further addition of Ca element was harmful to the strength. Among these alloys, the Mg-6Sn-2Zn alloy exhibited the best strength at room temperature in both as-cast and as-extruded states.

Highlights

Mg alloys have drawn attention in the past decades due to its advantage of having high strength–weight ratio, which helps its application in the transportation industry with improved fuel efficiency and reduced pollutant emission [1,2]
The effect of Zn and Ca addition on microstructure and strength at room temperature of Mg-Sn series alloy was investigated by comparison of as-cast and as-extruded Mg-6Sn, Mg-6Sn-2Zn, and Mg-6Sn-2Zn-1Ca alloys and the main conclusions are listed as follows
Microstructure of as-cast Mg-6Sn alloys was refined with the addition of Zn and Ca elements

Summary

Introduction

Mg alloys have drawn attention in the past decades due to its advantage of having high strength–weight ratio, which helps its application in the transportation industry with improved fuel efficiency and reduced pollutant emission [1,2]. Mg-Al alloys, such as the AZ and AM series, have been widely used due to their good corrosion resistance and qualified strength at room temperature. Over the past few years, Mg-rare earth (RE) alloys have shown good heat resistance and have been utilized successfully in the aerospace field. RE elements are efficient in improving the heat resistance of Mg alloys [5,6]. The price of RE elements is so high that it restricts further application of Mg-RE alloys. Mg-Sn alloys have received increasing investigation and interest as a novel heat-resistant Mg alloy, whose eutectic phase, Mg2 Sn phase, has a high melting point at 770 ◦ C [7,8,9]. The microstructure and strength at room temperature of novel Mg-Sn alloys is an emergent task to study

Methods

Discussion

Conclusion