Quench Sensitivity and Phase Transformation Kinetics of AlSi7MnMg High Pressure Vacuum Die Casting

Mengyun Liu,X.-Grant Chen,Francis Breton,Zhan Zhang,F De Geuser,P Jarry,G Salloum-Abou-Jaoude,C Sigli,L Salvo,A Deschamps,J.-C Ehrström

doi:10.1051/matecconf/202032602001

Mengyun Liu, X.-Grant Chen + Show 9 more

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https://doi.org/10.1051/matecconf/202032602001

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Abstract

The quench sensitivity of an AlSi7MnMg alloy in high-pressure vacuum die (HPVD) casting was investigated by time-temperature-transformation and time-temperature-property diagrams with an interrupted quench technique. The quench sensitive temperature range of the alloy is from 260 to 430 °C and its nose temperature is 350 °C. The mechanical strength versus cooling rates of the HPVD casting was predicted using quench factor analysis method and veriﬁed by experimental results. The critical cooling rate is 6 °C/s to remain 95% of the maximal mechanical strength. The coefﬁcientsk2-k5, related to the nucleation and precipitation kinetics of TTP curves, and phase transformation diagrams were determined. The precipitation of Mg2Si phase in the castings was observed during isothermal treatment using transmission electron microscope. Moreover, the quench sensitivity and kinetics of the phase transformation of AlSi7MnMg alloy and AlSi10MnMg alloys were compared. It reveals that the quench sensitivity and phase transformation rate of the former are lower than that of the latter.

Highlights

AlSi7MnMg (AuralTM-5) alloy has been widely applied in high pressure vacuum die (HPVD) castings due to its very good fluidity and castability, suitable for thin-wall and large complex cast structural components [1]
The AlSi7MnMg die casting alloy is heat-treatable and weldable, and its mechanical properties can be greatly enhanced through heat treatment, because the vacuum system used during the die casting process removes the entrapped air in die cavity during filling and limits the formation of blisters during solution heat treatment [2, 3]
During isothermal treatment, supersaturated aluminum matrix would decompose to form precipitates, which is corresponding to the changes in electrical conductivity (EC) of samples

Summary

Introduction

AlSi7MnMg (AuralTM-5) alloy has been widely applied in high pressure vacuum die (HPVD) castings due to its very good fluidity and castability, suitable for thin-wall and large complex cast structural components [1]. The AlSi7MnMg die casting alloy is heat-treatable and weldable, and its mechanical properties can be greatly enhanced through heat treatment, because the vacuum system used during the die casting process removes the entrapped air in die cavity during filling and limits the formation of blisters during solution heat treatment [2, 3]. Quenching is one of important steps in precipitationhardening heat treatment processes. It is important to select an optimal quenching rate in the heat treatment. Time-temperaturetransformation (TTT) and time-temperature-precipitate (TTP) diagrams are broadly used to study the quench sensitivity because these diagrams deliver important information, such as the critical time and nose temperature for precipitation during quenching [4]. An interrupted quenching technique with series of isothermal heating tests has been applied to construct

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