Characterizations of precipitation behavior of Al-Mg-Si alloys under different heat treatments

• Published in: China foundry Vol. 15; no. 2; pp. 89 - 96
• Main Authors: Li, Hui, Wang, Jia-yi, Jiang, Hai-tao, Lü, Zheng-feng, Zhu, Zhen-feng
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01-03-2018; Foundry Journal Agency; College of Engineering, Yantai Nanshan University, Yantai 265700, China; National Engineering Research Center for Plastic Working of Aluminum Alloys, Shandong Nanshan Aluminum Co., Ltd., Yantai 265713, China%Institute of Engineering Technology, University of Science and Technology Beijing, Beijing 100083, China%National Engineering Research Center for Plastic Working of Aluminum Alloys, Shandong Nanshan Aluminum Co., Ltd., Yantai 265713, China%College of Engineering, Yantai Nanshan University, Yantai 265700, China
• Subjects: Al-Mg-Si alloy; Alloys; Analysis; Electric properties; electrical resistivity; Engineering; Hardness (Materials); heat treatment; Machines; Manufacturing; Materials Engineering; Metallic Materials; Metals (Materials); precipitation behavior; Processes; Research & Development; Specialty metals industry; Al-Mg-Si alloy; A; precipitation behavior; heat treatment; electrical resistivity
• ISSN: 1672-6421; 2365-9459; 1672-6421
• DOI: 10.1007/s41230-018-7055-0

The solidification-precipitation behavior of Al-Mg-Si multicomponent alloys has long been an absorbing topic. Experiments were carried out to analyze the precipitation behaviors of Al-Mg-Si alloys under different heat treatments. All specimens were homogenized at 570 °C for 8 h, and then solution treated at 540 °C for 55 min. Subsequently, the specimens were age treated for different times at temperatures of 100 °C, 150 °C and 180 °C, respectively. The experimental results show that the occurrence of dispersed free zones (DFZ) is caused by the uneven distribution of dispersed phase. During the aging process, pre-β" phases form at the initial stage and an aging temperature of 100 °C is too low to complete the transformation of pre-β" to β". At 150 °C, the precipitation sequence is concluded as ssss-pre-β"-pre-β"+β"-β"-β'-β. Moreover, changes in sizes and densities of the pre-β", β"and β' phases during the aging process has an important influence on the evolution of microhardness and electrical resistivity. The microhardness peak value of 150 °C is similar to that of 180 °C, which is -141 HV. While, at 100 °C, the microhardness increases slowly, and the attainable value is 127 HV up to 19 days. When the aging temperature is 100 °C, the electrical resistivity has the highest average value. When the aging temperature exceeds 100 °C, with the occurrence and growth of P'and P', the resistivity has a distinct decrease with prolonged aging time.