Effect of Melt Overheating on Structure and Mechanical Properties of Al-Mg-Si Cast Alloy

Vladislav Deev,Evgeny Prusov,Xizhang Chen,Olga Prihodko,Svetlana Smetanyuk,Sergey Konovalov,Ernst Ri

doi:10.3390/met11091353

Abstract

The paper discusses the complex effect of melt overheating with subsequent fast cooling down to the pouring temperature on the crystallization process, microstructure and mechanical properties of Al-Mg-Si aluminum alloy. The results obtained facilitated the establishment of rational modes of melt overheating, leading to a significant change in the dispersion and morphology of structural components. In particular, with an increase in the melt overheating temperature to 900 °C with holding and subsequent rapid cooling to the casting temperature, a decrease in the average size of dendritic cells of the aluminum solid solution from 39 μm to 13 μm was observed. We also noticed the refinement of eutectic inclusions of the Mg2Si phase with compact morphology. An increased level of mechanical properties was noted; the maximum values of tensile strength and elongation reached 228 MPa and 5.24%, respectively, which exceeded the initial values by 22.5% and 52.3%, correspondingly. The microhardness of the aluminum solid solution sequentially increased from 38.21 to 56.5 HV with an increase in the temperature during melt overheating. According to the EDS linear scanning, an increase in the superheat temperature of the melt is accompanied by an increase in the degree of saturation of the solid solution with magnesium.

Highlights

It is well known that the quality of cast products made of aluminum alloys is largely determined by their structure
During the thermal-rate processing of AA 511 alloy melts, an important task is to search for modes that provide a modifying effect on both the dendritic cells of the α-solid solution and the excess phases of cryst5aollfi1-3 zation origin
During the thermal-rate processing of AA 511 alloy melts, an important task is to search for modes that provide a modifying effect on both the dendritic cells of the α-solid solution and the excess phases of crystallization origin

Summary

Introduction

It is well known that the quality of cast products made of aluminum alloys is largely determined by their structure. The mechanical and operational properties of aluminum alloys significantly depend on such structural factors like morphology, size, and distribution of structural components, including grains of an aluminum α-solid solution and various primary crystallizing phases [1,2,3] In this regard, the formation of a finegrained structure in castings is one of the ways to increase their properties and improve the quality of products from aluminum alloys [4,5,6]. From the point of view of technological implementation, the most convenient treatment is the processing of melts during melting [18]

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