Effects of Mold Materials on the Interfacial Reaction between Magnesium Alloy and Ceramic Shell Mold during Investment Casting

Yiwei Hao,Peixu Yang,Wenjie Zhang,Jiang Du,Jinxue Liu,Shaojun Zhang,Yang Xiao

doi:10.3390/met10080991

Yiwei Hao, Peixu Yang + Show 5 more

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https://doi.org/10.3390/met10080991

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Abstract

In order to suppress the interfacial reaction between the ceramic shell mold and the magnesium molten alloy during the investment casting process, a mold material with a high thermodynamic stability based on alkaline zirconium sol (CH4NO3Zr) binder and corundum (Al2O3) powder was prepared. The effects of the mold materials and casting thicknesses on the interfacial reaction were investigated by an optical microscope, X-ray diffraction, a scanning electron microscope, and an energy dispersive spectroscope analysis. The results suggested that the casting poured by the conventional ZrSiO4 mold has a serious reaction on the surface, and the reaction was more severe when the casting thickness was increased. The oxidation layer was approximately 300 μm in some severe areas of 45 mm thickness. The XRD and EDS results showed that the reaction interface mainly contains MgO and Mg2Si. While the casting poured by the Al2O3 mold provides a light and smooth surface, the reaction layer was only 1.5 μm on average. The reaction interface mainly contains MgO and Mg2F.

Highlights

Nowadays, the rapid development of material design and functionalization has aroused the widespread concern of scientists [1,2,3]
It is especially necessary to consider the thermodynamic stability of the shell mold, because magnesium alloy is extremely reactive in the molten state and is prone to oxidation and reacting with mold materials, resulting in serious mold-metal reactions [7]
It can be seen that the casting surface is pretty dark for the ZrSiO4 mold (Figure 3a,c)

Summary

Introduction

The rapid development of material design and functionalization has aroused the widespread concern of scientists [1,2,3]. Investment casting is one of the reasonable solutions for the near net shaping of magnesium alloys. This process has been widely used in the aerospace industry in applications such as engine valves, vanes, turbochargers, and aero-engines due to its superior dimensional accuracy and small surface roughness [4,5]. It is especially necessary to consider the thermodynamic stability of the shell mold, because magnesium alloy is extremely reactive in the molten state and is prone to oxidation and reacting with mold materials, resulting in serious mold-metal reactions [7]. The reaction would reduce the casting surface accuracy and cause a deterioration of the mechanical properties [7,8]

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