Effect of cooling rates of production process of Al-3%B-3%Sr master alloy on grain refinement and eutectic modification efficiency in cast A356 alloy

Krittee Eidhed,Phisith Muangnoy,C Hamontree

doi:10.1051/matecconf/201819201036

Krittee Eidhed, Phisith Muangnoy + Show 1 more

Open Access

https://doi.org/10.1051/matecconf/201819201036

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Abstract

In this paper, size and morphology of the grain refiner and modifier particles in the Al-3%B-3%Sr master alloy production by using different cooling rates were investigated. Two Al-3%B-3%Sr master alloys were produced with 0.2 and 10°C/s, respectively. The grain refinement and eutectic modification efficiency of the Al-3%B-3%Sr master alloy were tested in casting process of A356 alloy by addition of 4wt.% and holding times for 10-120 min. The experimental result showed that microstructure of the M1 alloy (Slow cooling) consisted of larger solidified particles of AlB2, SrB6and Al4Sr in the matrix of α-Al compared to the M2 alloy (Rapid cooling). The addition of the M1 alloy in cast A356 alloy, it was found that small grain size and fully modify eutectic silicon were obtained from the holding time in a range of 10-60 min. While the addition of M2 alloy, a small grain size was achieved in shorter holding time in a range of 10-30 min but the eutectic silicon was partly modify. From the thermal analyzed result, solidification of un-modified A356 alloy was changed after addition of Al-3%B-3%Sr master alloy. It was clearly observed that both the undercooling of nucleation and eutectic reaction was reduced and the solidification time was shifted to longer.

Highlights

Al-Si-Mg/Al-Si-Cu based alloys are widely used for cast complex part because of an excellent castability, resistance to hot tearing in casting, enhance mechanical properties by using the precipitation strengthening by controlling the precipitated particle of Mg2Si or Al2Cu [1]
Upon addition with Al-Sr alloy, it was dissolve into the melt and form the SrAl2Si2 compound [11] which increases the impurity twining for changed eutectic Si from acicular into a fibrous morphology
This paper studied the effect of cooling rates on size and morphology of AlB2 and SrB6 particles in production of Al-3%B-3%Sr master alloy

Summary

Introduction

Al-Si-Mg/Al-Si-Cu based alloys are widely used for cast complex part because of an excellent castability, resistance to hot tearing in casting, enhance mechanical properties by using the precipitation strengthening by controlling the precipitated particle of Mg2Si or Al2Cu [1]. The eutectic modification process can be improvement mechanical properties, the die filling, controlling the porosity distribution [7,8] and reducing the solution heat treatment in the age hardening process [9] Other elements such as Cr can refine the eutectic silicon the sludge phase can form with high Cr content and slow cooling rate [10]. There are many grain refiner and modifier were developed such Al-Ti-B-Sr and Al-B-Sr master alloys by producing various types of particles such as TiB2, TiAl3, AlB2 and SrB6 as the heterogeneous nucleation site and modification in the melt treatment process, simultaneously. The size and morphology of various phases in the master alloy production depend on the melting temperature, cooling rate, chemical compositions and casting method. The comparison of grain refinement and eutectic modification efficiency in cast A356 alloy were discussed

Experimental procedures

Result and discussion

Conclusions