Abstract
The microstructures of high-Si Al alloy cylindrical simples produced by rheological squeeze-casting with bottom-up filling were investigated. The effect of process parameters on the distribution of hard phases (primary Si and Fe-rich phase) was evaluated, and flow characteristics of semi-solid slurry of high-Si Al alloy were investigated. Differences in volume fractions (VFs) of hard phases between the middle and upper layers of cylindrical samples decreased as the squeezing speed increased. Moreover, the flow state of the semi-solid alloy slurry transitioned from laminar to turbulent flow as the squeezing speed was increased. Movement of gases throughout the semi-solid alloy slurry filling process was analysed under different process parameters. The results provide insights for improving rheological casting of high-Si Al alloy and other Al matrix composites.
Highlights
IntroductionHigh Si Al alloys (hypereutectic Al-Si alloys) are alloy systems with Al and Si as the main elements, for example, the commonly used commercial alloy A390
High Si Al alloys are alloy systems with Al and Si as the main elements, for example, the commonly used commercial alloy A390
Evaluation of Microstructural Characteristics of High-Si Al Alloy Cylindrical Samples Produced by Rheological Squeeze Casting with Bottom-Up Filling and Flow State Analysis of the Alloy Semi-Solid Slurries compact, in specimens obtained using a final pressure of 160 MPa
Summary
High Si Al alloys (hypereutectic Al-Si alloys) are alloy systems with Al and Si as the main elements, for example, the commonly used commercial alloy A390 Solidification microstructures of this series of alloys are mainly comprised of primary Si, primary α-Al, and eutectic phases[1,2]. Hypereutectic alloys have a wide temperature range in which the Si phase and liquid phase can coexist, and this can lead to gas and shrinkage porosity during squeeze casting or die-casting[8]. These distinct material characteristics and material forming properties greatly limit the commercial application of high Si Al alloy
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