Barothermography and microstructure of the hypoeutectic and eutectic alloys in Al–Si system
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Differential barothermal analysis (DBA or HP-DTA) of the phase transformations in hypoeutectic Al-10 at.% Si and eutectic Al-12 at.% Si alloys was carried out at 100 MPa of argon pressure and at temperatures up to 700 °C. Liquidus temperature of Al-10 at.% Si is reduced during melting and crystallization by 3–4 °C as compared with the atmospheric pressure data. Increase in the eutectic transformation L → (Al) + Si temperature up to 580–581 °C during heating was found for the Al-10 at.% Si and Al-12 at.% Si alloys. According to the barothermography data, a slight thermal effect at 553 °C is detected for both alloys, which was identified as the decomposition of aluminum-based solid solution and precipitation of silicon particles. The improvement of silicon phase morphology for Al-10 at.% Si and Al-12 at.% Si alloys after hot isostatic pressing (HIP) at the pressure of 100 MPa and temperature of 550 °C was found. No porosity in the alloy has been established after HIP treatment. After HIP thermal expansion, coefficients of the alloy are noticeably decreased by 25 (Al-10 at.% Si) and 50 % (Al-12 at.% Si).
KeywordsAluminum alloys Silumins Thermal analysis Hot isostatic pressing Microstructure Thermal expansion coefficient
The research was supported by Russian Foundation for Basic Research, Grant No. 11-03-00689-a, and by the Program for Basic Research of Russian Academy of Sciences Department of Chemistry and Materials Science.
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