The Effect of Holding Time After Sr Addition on Microstructural and Mechanical Properties of A356 Alloy

Sezgin Yaşa,Yahya Bayrak,Mustafa Çiğdem,Ahmet Kabil

doi:10.5505/pajes.2020.04557

Abstract

The spheroidization of the silicon eutectic phase in aluminum is an important parameter for casting and significantly influences the material properties. Sr has been used for a long time for eutectic modification in aluminum and many researches have been made on this subject. In this study, the effect of holding time after Sr addition on the mechanical properties and eutectic phase modification of the aluminum were investigated. 200 ppm Sr was chosen as the amount of Sr and the holding times were chosen as 20, 40 and 80 minutes. Tensile test was performed for the determination of mechanical properties and ultimate tensile strength and percentage of elongation values were measured. In order to quantify eutectic modification, the length / width (aspect ratio) ratios of eutectic silicon particles were measured. In addition, Bifilm Index of the molten metal was determined with the reduced pressure test (RPT). With the increase in the holding time, an increase in the aspect ratio and in the Bifilm Index was measured. It has been observed that the tensile strength and elongation values have decreased as the holding time has increased.

Highlights

The use of aluminum alloys in technical use is quite common and especially Al-Si alloys are popular among them [1]
The mechanical properties of aluminum alloys are determined by microstructural components for instance secondary dendrite arm spacing (SDAS), intermetallic compounds, porosity and eutectic phases
It was proved by the study of J H Zhang et al [10] that Sr amount in the melt decreased with increasing holding time and the modification rate decreased

Summary

Introduction

The use of aluminum alloys in technical use is quite common and especially Al-Si alloys are popular among them [1]. The mechanical properties of aluminum alloys are determined by microstructural components for instance secondary dendrite arm spacing (SDAS), intermetallic compounds, porosity and eutectic phases. Eutectic modification in these alloys is done by adding elements such as Na, Sb and Sr to the molten metal in the form of master alloys. Sr modification enhances the mechanical properties of aluminum alloy by refining eutectic silicon phase from plate to a fine morphology [6]. It is well known that the plate-like eutectic Si phase have detrimental effect on the mechanical properties of Al-Si cast alloys especially for the ductility. Effect of holding time after Sr addition on microstructural and mechanical properties of A356 alloy has been investigated

Experimental methods

Results and discussion

Conclusions