Microstructure and Properties of Al-12.7Si-0.7Mg Alloy Extrusion after End-Quenching Test

Abstract:

The cooling temperature field, microstructure and properties of an Al-12.7Si-0.7Mg alloy extrusion after an end-quenching experiment at 540 ^oC were investigated by means of an end-quenching test, hardness test, electrical conductivity determination and TEM observations. The results showed that the cooling rate of the alloy extrusion decreases sharply as the distance from the end-quenching spray point increased, when the distance from the end-quenching spray point is within 70 mm. Additionally, the cooling rate of the alloy extrusion decreased slowly along the length of the alloy extrusion when the distance from the end-quenching spray point exceeded 90 mm. The cooling rate of the alloy extrusion at distances of 20 mm and 32.5 mm from the end-quenching spray point exceeded 34 ^oC/s and 24 ^oC/s, respectively. Both hardness and electrical conductivity of the alloy extrusion within 32.5 mm from the end-quenching spray point were comparable to those of the alloy extrusion of off-line quenching at over 520 °C. There was no obvious precipitate in the alloy extrusion matrix 20 mm from the end-quenching spray point, and there were few fine and heterogeneous short rod-like precipitates in the alloy extrusion matrix 32.5 mm from the end-quenching spray point. However, there were many precipitates with lengths of approximately 10 nm in the alloy extrusion matrix 45 mm from the end-quenching spray point, and the lengths of the precipitates increased to approximately 20 nm when the distance from the end-quenching spray point exceeded 57.7 mm. The critical cooling rate of the 4-mm thick Al-12.7Si-0.7Mg alloy extrusion should exceed 24 ^oC /s.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 1945-1950
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.1945
• Online since: November 2016
• Authors: Ni Tian*, Tao Hong, Gang Zhao, Fu Xiao Yu, Liang Zuo
• Keywords: Al-Si Alloy Extrusion, Electrical Conductivity, End-Quenching Test, Hardness, Microstructure

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