Formation causes and preventive measures for MgO defects of 7075 aluminum alloy rolled sheet
Luo Chaoqing;Zheng Xu;Yao Xiang;Tan Zimeng;He Kezhun;Guangxi Alnan Aluminium Co., Ltd.;Guangxi Key Laboratory of Aluminum Alloy Materials and Processing;
Ultrasonic testing equipment was used to inspect the 7075 aluminum alloy before and after rolling, and the defects were analyzed by optical microscope, scanning electron microscope and energy dispersive spectroscope. The analysis results showed that the defects were MgO inclusions. The ultrasonic testing of the ingot conformed to the ASTM B594-2019 A standard, but the quality was not acceptable after the ingots were rolled into sheets and solution quenching, indicating that the ultrasonic equivalent of this defect increased after hot working. Mg is an easily oxidizable element. During the melting and casting process of aluminum alloys, the surface of the high-temperature aluminum liquid contacts the air to undergo an oxidation reaction to form MgO, which enters the ingot during the casting process to form MgO inclusions. During the casting process, control measures should be taken to avoid the generation of MgO inclusions, such as controlling the stirring intensity, raising the casting temperature, controlling the amount of Ar-Cl_2 mixed gas injection and adopting a filtering device.