Effects of Solution Treatment Time on Mechanical Properties of Cast Al-Si-Mg Alloy at Low Temperature
The low temperature tensile test of cast Al-7Si-0.3Mg alloy was carried out.The effect of solid solution time on the mechanical properties and microstructures of Al-7Si-0.3Mg alloy at 20 ℃,-20 ℃ and-60 ℃was investigated,and the effect of Si on the fracture behavior and its mechanism were analyzed.The results showed that with prolonging in the solution time,the yield strengths,tensile strengths and elongations of the alloys at 20 ℃,-20 ℃ and-60 ℃ increased firstly and then decreased,and the maximum value could be obtained with the solution time of 10 h.With prolonging in the solution time,the size of Si phase and the ratio of length to width decreased.When the solid solution time was 10 h,the smaller Si phase in the alloy exhibited mainly granular shape,and with increasing the solution time to 15 h the size and length-width ratio of Si phase were increased.With the decrease of the test temperature,the number of slip bands near the Si phase showed a decreasing trend,and there were more fracture Si phases near the fracture surface at low temperature.Fracture Si exhibited the smaller cracks when the solid solution time was 10 h,the fracture is dominated by small cleavage plan and dimple.The toughness was better than that of ones without solution.
Al-7Si-0.3Mg alloysolution treatmentSi phaselow temperature tensile
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