Effect of bifilm defects on Microstructure and Tensile properties of A356 secondary alloy for the recycling of machining chip scrap
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With the growing demand for aluminum alloys, interest in recycling aluminum is increasing due to economic and environ-mental reasons. In order to evaluate the recyclability of machining chip scrap, microstructural analysis and tensile tests of A356 cast alloys with different scrap fraction of 0, 20, 40, 60, 80, and 100% were conducted. The secondary dendrite arm spacing increased from 26.21 to 36.34 μm as the scrap content increased. The microstructure comprised an α-Al matrix, eutectic Si, α-Al8Fe2Si, β-Al5FeSi, and π-Al8Mg3FeSi6, which possess similar microstructures to those of commercial A356 cast alloys. The test results showed that the size and number of pores increased with the increasing scrap content. When the scrap content was higher than 40%, the pore area fraction increased significantly up to 5.97% for 100% scrap. It was shown that increasing the scrap content decreased the average tensile strength, yield strength, and elongation to 94.34 MPa, 72.10 MPa, and 5.22%, respectively. The porosities and tensile strengths of A356 alloy without scrap content were considered to have similar values to 20% scrap contents. Pores were found on the fracture surfaces under all the conditions.
Abstract
With the growing demand for aluminum alloys, interest in recycling aluminum is increasing due to economic and environ-mental reasons. In order to evaluate the recyclability of machining chip scrap, microstructural analysis and tensile tests of A356 cast alloys with different scrap fraction of 0, 20, 40, 60, 80, and 100% were conducted. The secondary dendrite arm spacing increased from 26.21 to 36.34 μm as the scrap content increased. The microstructure comprised an α-Al matrix, eutectic Si, α-Al8Fe2Si, β-Al5FeSi, and π-Al8Mg3FeSi6, which possess similar microstructures to those of commercial A356 cast alloys. The test results showed that the size and number of pores increased with the increasing scrap content. When the scrap content was higher than 40%, the pore area fraction increased significantly up to 5.97% for 100% scrap. It was shown that increasing the scrap content decreased the average tensile strength, yield strength, and elongation to 94.34 MPa, 72.10 MPa, and 5.22%, respectively. The porosities and tensile strengths of A356 alloy without scrap content were considered to have similar values to 20% scrap contents. Pores were found on the fracture surfaces under all the conditions.
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