Constitutive model for AZ31 magnesium alloy based on isothermal compression test

Abstract

Isothermal compression tests at temperatures ranging from 523 to 723 K and strain rates from 0·01 to 10 s⁻¹ were performed on AZ31 magnesium alloy to reveal the deformation characteristics. The flow stress–strain curves show that the flow stress reaches a peak value and then decreases to steady values, which characterise a dynamic flow softening. The measured flow stress was modified by friction and temperature correction, which reflect the friction corrected flow stresses are lower than the measured ones and the effect of temperature rise on flow stress is obvious at high strain rate (≧1 s⁻¹). The corrected flow curves were employed to develop the constitutive model. The influence of strain was also incorporated in the constitutive equation by considering the effects of strain on material constants, which were identified using sixth order polynomial. The flow stress predicted by the constitutive model shows good agreement with the corrected stress, which confirmed that the proposed model is effective and accurate for the flow stress of AZ31 magnesium alloy.

Keywords:

• AZ31 magnesium alloy
• Hot deformation
• Constitutive model
• Flow stress

This research was supported by the National Natural Science Foundation of China (grant nos. 50831008 and 51105029). The authors thank the Key Laboratory for Advanced Materials Processing Technology, Tsinghua University, Beijing, China, and also Dr K. Chung at Seoul National University in Korea for his assistance in revising the manuscript.