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Effects of Solidification Pressure and Heat Treatment on the Microstructure and Micro-Hardness of AlSi9CuMg Alloy

1
School of Material Science and Engineering, Beihang University, Beijing 100083, China
2
Material Department, AVIC Manufacturing Technology Institute, Beijing 100024, China
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(14), 2229; https://doi.org/10.3390/ma12142229
Received: 12 June 2019 / Revised: 2 July 2019 / Accepted: 5 July 2019 / Published: 10 July 2019
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Abstract

The effect of high pressure (135 MPa) and the following heat treatment on the microstructure and micro-hardness of the squeezing cast AlSi9CuMg alloy is investigated, using optical microscopy (OM), Vickers tester, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicate that the application of high pressure can increase under-cooling and the cooling rate during solidification and cause the refinement of the microstructure. The enhanced melt flow resulting from high pressure can also break the dendrite to form the spherical and elliptical primary α (Al) grains during the early stage of solidification. The winter-sweet flower-shaped primary α (Al) phases can also be formed through plastic deformation caused by the flow of the partially solidified melt. The ageing treatment results showed that a maximum (peak) micro-hardness value was obtained for each of the three ageing temperatures at different ageing times, and the highest peak value was achieved at 175 °C for 480 min. The micro-hardness change of the sample under different ageing processes was attributed to the variation of type, density, and size of the precipitates. View Full-Text
Keywords: squeezing casting; high pressure; melt flow; solid solution; strengthening squeezing casting; high pressure; melt flow; solid solution; strengthening
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Wei, L.; Han, B.; Ye, F.; Xu, Y.; Wu, S. Effects of Solidification Pressure and Heat Treatment on the Microstructure and Micro-Hardness of AlSi9CuMg Alloy. Materials 2019, 12, 2229.

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