Microstructures, Mechanical and Corrosion Properties of the Extruded AZ31-xCaO Alloys

Yalin Lu,Mengqi Cong,Yang Zhang,Wenting Xu,Leipeng Song,Xingcheng Li

doi:10.3390/ma11081467

Abstract

The effects of the extrusion process and CaO addition amount on microstructure, mechanical, and corrosion properties of AZ31 alloys were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), standard tensile testing, and so on. The grain size of AZ31 or AZ31-1%CaO alloy becomes larger with increasing extrusion temperature. The grain size of AZ31-1%CaO alloy is much smaller than that of AZ31 alloy at the same extrusion temperature. In addition, the formation of the Al2Ca phase caused by CaO addition refines the grain size, and the recrystallization of AZ31-1%CaO alloy is improved significantly. The recrystallization grains distribute more uniformly as the increase of extrusion ratio, and the completely recrystallized grains distribute uniformly in the form of equiaxed crystals with an extrusion ratio of 9. Tensile testing results show that extruded AZ31-1%CaO alloy at the extrusion temperature of 300 °C and an extrusion ratio of 9 exhibits the best mechanical properties. While corrosion properties of AZ31 alloys decreases due to the addition of CaO.

Highlights

Mg alloys are widely applied in the fields of automotive and aerospace due to their specific strengths and low density
Because the alloying element is difficult to handle due to its high reactivity in atmospheric conditions, some oxides are developed for ignition-proof magnesium alloy [10,11]
AZ31 Mg alloy was melted in a steel crucible while using an electric resistance furnace at 720 ◦ C under a mixture gas of SF6 and CO2, and CaO was added into the melting

Summary

Introduction

Mg alloys are widely applied in the fields of automotive and aerospace due to their specific strengths and low density. Mg-Al-Zn (AZ) or Mg-Al-Mn (AM) alloys, while they are limited because of poor strength and corrosion resistance [1,2,3]. Rapid ignition that is caused by serious oxidation of magnesium at high temperature is a big problem [4,5]. Be [6], Re [7,8], Ca [9], and so on, are added into Mg alloys, reducing the oxidation of magnesium melting. Adding alloying elements can reduce the use of SF6 and CO2 gas causing a global thermal effect. Because the alloying element is difficult to handle due to its high reactivity in atmospheric conditions, some oxides are developed for ignition-proof magnesium alloy [10,11]

Methods

Results

Conclusion