Acta Metallurgica Sinica (English Letters) ›› 2023, Vol. 36 ›› Issue (2): 281-294.DOI: 10.1007/s40195-022-01471-x

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Abnormal Twinning Behavior and Constitutive Modeling of a Fine-Grained Extruded Mg-8.0Al-0.1Mn-2.0Ca Alloy under High-Speed Impact along Various Directions

Fei-Yang Chen1,2, Peng-Cheng Guo1,3(), Zi-Han Jiang1, Xiao Liu4, Tie-Jun Song3, Chao Xie2()   

  1. 1College of Mechanical and Electrical Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
    2College of Mechanical Engineering and Mechanics, Ningbo University, Ningbo, 315211, China
    3College of Mechanical Engineering, Xiangtan University, Xiangtan, 411105, China
    4College of Material Science and Engineering, Hunan University of Science and Technology, Xiangtan, 411201, China

Abstract:

To understand the mechanical and twinning behaviors of a fine-grained extruded Mg-8.0Al-0.1Mn-2.0Ca alloy under high-speed impact, impact tests were carried out using a split Hopkinson pressure bar, and microstructures at strains of 0.05, 0.10 and 0.20 were obtained using a series of stop rings manufactured by high-strength steel. The stress response and twinning behavior are closely related to loading direction and applied strain rate. The true stress-true strain curves are s-shaped in extrusion direction (ED) and c-shaped in transverse direction (TD), showing apparent anisotropy, while the yield strength is insensitive to loading direction. Almost identical strain-rate sensitivity is demonstrated by the stress in ED and TD. Interestingly, de-twinning is apparent as the applied strain increases to 0.20, and it is enhanced with increasing the applied strain rate. In contrast, the twin density in ED samples is clearly higher than that in TD samples. By modifying the terms of strain hardening and strain rate hardening in the classical JC model, an optimized model is built, which can accurately predict the stress response behavior of the studied alloy under high-speed impact along ED and TD. The correlation coefficient (R) and average absolute relative error (AARE) are 98.63% and 0.0199 for ED, and 96.88% and 0.0202 for TD, respectively.

Key words: High-speed impact, Magnesium alloy, Twinning behavior, Constitutive model, Anisotropy