Hot Deformation Behavior and Processing Maps of As-Cast Hypoeutectic Al-Si-Mg Alloy
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JMEPEG https://doi.org/10.1007/s11665-019-04229-2
Hot Deformation Behavior and Processing Maps of As-Cast Hypoeutectic Al-Si-Mg Alloy Zhenglong Liang, Qi Zhang, Liqun Niu, and Wei Luo (Submitted October 30, 2018; in revised form March 1, 2019) The hot deformation behavior of as-cast hypoeutectic Al-Si-Mg alloy has been investigated through hot compression tests at temperatures between 573 and 773 K and the strain rate of 0.001-1 s21. A modified Hansel-Spittel constitutive model is proposed, which takes the effect of strain rate on strain hardening into account. The processing maps are established based on the dynamic material model and the Murty criterion. Microstructure observations show that dynamic recovery dominates the dynamic softening behavior, and recrystallized grains are found in the sample tested at 773 K with strain rate of 0.01 and 0.001 s21. The size of Si particles decreases by about 64.73% with the effective strain increasing from 0 to 1.2. The optimal hot processing parameters of as-cast hypoeutectic Al-Si-Mg alloy are established based on the processing maps. Keywords
dynamic recovery, Hansel-Spittel model, hot deformation behavior, hypoeutectic Al-Si-Mg alloy, processing maps
1. Introduction Hypoeutectic aluminum alloys with silicon amount of 7-9% are the most widely used foundry alloys in automotive and aerospace applications due to their high strength-to-weight ratio, good castability and possibility of precipitation strengthening (Ref 1-4). The mechanical properties of those alloys greatly depend on the morphology and distribution of Si phase and primary aluminum dendrites as well as casting defects (Ref 5, 6). Severe plastic deformation methods, such as friction stir process (Ref 7), hot extrusion (Ref 8), equal channel angular pressing (Ref 9) and casting-forging process (Ref 10, 11), were found to be effective in refining casting features and eliminate casting defects, thereby enhancing mechanical properties (Ref 12). In order to acquire uniform and defect-free microstructure, it is quite necessary to investigate hot deformation behavior and evaluate workability of those alloys for optimizing the forming parameters of the processes. Constitutive model is an effective method to depict the relationship between the deformation behavior and external loadings, such as strain, strain rate and temperature. In recent years, many constitutive models have been proposed to delineate the hot deformation behavior of those alloys (Ref 13). Haghdadi et al. proposed a strain-compensated Arrhenius-type constitutive model for modeling the flow behavior of A356 alloy at elevated temperature (Ref 14). A modified Johnson-Cook constitutive model for Al-Si-Mg alloy which takes the effect of strain rate on thermal softening into account was developed by Liang Ref 15. Lin et al. established a Zhenglong Liang, Qi Zhang, Liqun Niu, and Wei Luo, School of Mechanical Engineering, XiÕan Jiaotong University, XiÕan 710049, China. Contact e-mail: [email protected].
Journal of Materials Engineering and Performance
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