Effects of processing parameters on microstructure and ultimate tensile strength of thixoformed AM60B magnesium alloy

Ti Jun Chen,Rui Quan Wang,Yuan Hao,Ying Ma

doi:10.1590/s1516-14392012005000079

Abstract

The effects of processing parameters, such as the punch speed, reheating duration and reheating temperature, on microstructure and ultimate tensile strength (UTS) of thixoformed AM60B magnesium alloy have been investigated. The results indicate that low punch speed, short reheating duration or low reheating temperature often produces the defect of cold shuts or shrinkage porosities. On the contrary, gas pores can easily form. In addition, the reheating duration or temperature also has obvious effects on the primary particle size, fraction and morphology. The three parameters can significantly affect the UTS due to their effects on the formation of pores (cold shuts, shrinkage porosities and gas pores). But they can not alter the fracture path during tensile testing and the path is always along the secondarily solidified structures between the primary particles. The effect of pore amount on the UTS is lager than that of the primary particle size, fraction or morphology. In view of their effects on the microstructure compactness and the resultant UTS, the optimized parameters are reheating for 130 minutes at 610 °C and punch speed of 3 m/s.

Highlights

Magnesium alloys have large potential in fabrication of structural components of automobiles due to their high specific strength[1]
It is well known that thixoforming, a relatively new metal forming technology, can significantly improve mechanical properties of aluminium alloys and a large number of thixoformed aluminum alloy components has been applied to automobiles[3,4]
It is surprised that the elongation of thixomoulded AZ91D magnesium alloy is obviously improved while its ultimate tensile strength is equivalent to or less than that of the traditional die casting or permanent mould casting alloy[5]

Summary

Introduction

Magnesium alloys have large potential in fabrication of structural components of automobiles due to their high specific strength[1]. They have wide applications in the fields of electronic products, portable tools, sporting goods and aerospace vehicles[2]. It is well known that thixoforming, a relatively new metal forming technology, can significantly improve mechanical properties of aluminium alloys and a large number of thixoformed aluminum alloy components has been applied to automobiles[3,4]. A query if magnesium alloys are adequate to be thixoformed is arising To clarify this problem, the relations between processing parameters, resultant microstructure and mechanical properties should be studied. Study on the detailed effects of processing parameters on microstructure (including casting defects) and mechanical properties has not been found

Methods

Results

Conclusion