Microstructure, Fracture Mechanism, and Constitutive Analysis of Spray-Formed and Extruded Al-12Zn-2.4Mg-1.1Cu-0.3Zr All
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Microstructure, Fracture Mechanism, and Constitutive Analysis of Spray-Formed and Extruded Al-12Zn-2.4Mg-1.1Cu-0.3Zr Alloy Li Yang, Wangzhang Lu, Yaocheng Zhang, Zheng Liu, Di Wei, Feng Xu, Song Pang, and Ruifeng Li Submitted: 9 August 2020 / Revised: 28 September 2020 / Accepted: 11 October 2020 The microstructure, hot flow stress behavior, and fracture mechanism of spray-formed and extruded (SFEed) Al-12Zn-2.4Mg-1.1Cu-0.3Zr alloy were investigated by uniaxial tensile stress over temperature range 523-673 K and strain rate range 0.00005-0.05 s21. The interaction among activation energy and deformation parameters was analyzed. An Arrhenius-based constitutive equation was proposed to determine the peak flow stress of SFEed Al-12Zn-2.4Mg-1.1Cu-0.3Zr alloy. The results reveal that the recrystallization degree and MgZn2 phase content as well as dislocation density for various deformation conditions are vital for peak flow stress. The studied alloy exhibits superior peak flow stress by the high alloying elements and RRA heat treatment. The transformation of fracture mechanism from void coalescence to intergranular fracture is mainly caused by the interaction between dislocation and MgZn2 phase. Low activation energy on the case of high temperature is contributed by the reduction of energy barrier for dislocation motion caused by microstructure evolution. The proposed constitutive equation can determine the peak flow stress with reasonable precision by analysis of standard statistical parameters. Keywords
activation energy, constitutive equation, fracture mechanism, peak flow stress, SFEed Al-12Zn-2.4Mg-1.1Cu-0.3Zr alloy
1. Introduction Al-Zn-Mg-Cu alloys have been extensively applied for the structural compounds in aerospace applications and mobile manufacturing because of superb specific strength, excellent stress corrosion cracking resistance, and processability (Ref 13). The researches of Al-Zn-Mg-Cu alloys focused on enhancing both ductility and strength in the past decades, and the strength of Al-Zn-Mg-Cu alloys was improved by adding alloying elements to produce solid-solution strengthening and precipitation hardening, such as Zn (Ref 4, 5), Mg (Ref 6, 7), Li Yang, School of Mechanical Engineering, Guilin University of Aerospace Technology, Guilin 541004, PeopleÕs Republic of China; and Jiangsu Key Laboratory of Recycling and Reuse Technology for Mechanical and Electronic Products, Changshu Institute of Technology, Jiangsu 215500, PeopleÕs Republic of China; Wangzhang Lu, School of Mechatronic Engineering, China University of Mining and Technology, Jiangsu 221000, PeopleÕs Republic of China; Yaocheng Zhang, Di Wei, and Feng Xu, Jiangsu Key Laboratory of Recycling and Reuse Technology for Mechanical and Electronic Products, Changshu Institute of Technology, Jiangsu 215500, PeopleÕs Republic of China; Zheng Liu, School of Mechanical Engineering, Guilin University of Aerospace Technology, Guilin 541004, PeopleÕs Republic of China; Song Pang, Shanghai Spaceflight Precision Machinery Inst
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