Hot deformation behavior and optimization of processing parameters of a high-strength Mg-Gd-Nd-Zn-Sn-Zr alloy
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ORIGINAL ARTICLE
Hot deformation behavior and optimization of processing parameters of a high-strength Mg-Gd-Nd-Zn-Sn-Zr alloy Zehua Yan1,2 • Yandong Yu1,2 Yiming Yao1,2
•
Jiahao Qian1,2 • Yanchao Sang1,2
•
Received: 22 February 2020 / Accepted: 14 July 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract Aiming at the forward extrusion forming and its parameter optimization of high-strength and heat-resistant Mg-9Gd-3Nd-1Zn-1Sn-0.5Zr alloy, the isothermal compression stress–strain behavior was investigated. The hightemperature plastic deformation constitutive equation and the microstructure evolution of the alloy were obtained. According to the results of variation of stress–strain with strain rates and processing temperatures, a thermal processing map of the alloy was constructed, to obtain a safe processing area where the material is not prone to be unstable. Based on the results of thermal processing map, the experiments were carried out with the punching speed of 2 mm/s, the temperatures of 400 °C, 425 °C and 450 °C and the extrusion ratio of 12. The results showed that the best comprehensive properties of the alloy were obtained at the extrusion temperature of 425 °C. In addition, our findings were in good agreement with the prediction of the thermal processing map. Keywords Mg-9Gd-3Nd-1Zn-1Sn-0.5Zr alloy Microstructure Constitutive equation Thermal processing map Extrusion
& Yandong Yu [email protected] 1
Department of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, People’s Republic of China
2
Key Laboratory of Advanced Manufacturing and Intelligent Technology, Ministry of Education, Harbin 150040, People’s Republic of China
1 Introduction Casting is one of the remarkably important part in magnesium alloy forming method [1–3]. However, solidification defects and poor room temperature plasticity of as-cast magnesium alloys make them unsuitable to be applied in structural materials [4, 5]. High-temperature plastic deformation methods, such as extrusion, forging, rolling and other processes, are effective to prepare magnesium alloy products with improved mechanical properties and eliminating casting defects [6–13]. Meanwhile, elevated temperature can provide energy for activating the non-base surface slip and grain boundary slipping, and thus the plasticity of magnesium alloys is improved [14]. Relevant studies show that magnesium alloys are sensitive to strain rate and deformation temperature; therefore, deformation parameters are important to obtain more outstanding comprehensive performance of the products [15, 16]. Recently, various heat-resistant magnesium alloys have been successfully developed to meet the requirements of high strength, such as WE43 alloys, which have already been brought in to commercial use. With the development of Mg-RE alloys, lots of new alloys have been developed, especially for those with high Gd content [17–23]. However, addition of RE in magnesium alloy will increase costs. Considering that adding an appropri
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