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Material model optimization for dynamic recrystallization of Mg alloy under elevated forming temperature

마그네슘 합금의 온간 동적재결정 구성방정식 최적화

  • Cho, Yooney (Department of Mechanical engineering, Hanyang University ERICA campus) ;
  • Yoon, Jonghun (Department of Mechanical engineering, Hanyang University ERICA campus)
  • 조윤희 (한양대학교 ERICA 캠퍼스 기계공학과) ;
  • 윤종헌 (한양대학교 ERICA 캠퍼스 기계공학과)
  • Received : 2017.02.21
  • Accepted : 2017.06.09
  • Published : 2017.06.30

Abstract

A hot forming process is required for Mg alloys to enhance the formability and plastic workability due to the insufficient formability at room temperature. Mg alloy undergoes dynamic recrystallization (DRX) during the hot working process, which is a restoration or softening mechanism that reduces the dislocation density and releases the accumulated energy to facilitate plastic deformation. The flow stress curve shows three stages of complicated strain hardening and softening phenomena. As the strain increases, the stress also increases due to work hardening, and it abruptly decreases work softening by dynamic recrystallization. It then maintains a steady-state region due to the equilibrium between the work hardening and softening. In this paper, an efficient optimization process is proposed for the material model of the dynamic recrystallization to improve the accuracy of the flow curve. A total of 18 variables of the constitutive equation of AZ80 alloy were systematically optimized at an elevated forming temperature($300^{\circ}C$) with various strain rates(0.001, 0.1, 1, 10/sec). The proposed method was validated by applying it to the constitutive equation of AZ61 alloy.

Keywords

AZ80;AZ61;dynamic recrystallization;material model;optimization;thermo-mechanical flow curve

Acknowledgement

Supported by : 한국연구재단

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