An Accurate Constitutive Model for AZ31B Magnesium Alloy during Superplastic Forming

Guangwen Dai,Fahrettin Ozturk,Jamal Sheikh-Ahmad,Firas Jarrar,Zemin Li

doi:10.3390/met9121273

Guangwen Dai, Fahrettin Ozturk + Show 3 more

Open Access

https://doi.org/10.3390/met9121273

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Abstract

Accurate constitutive material models are essential for the realistic simulation of metal forming processes. However, for superplastic forming, mostly the material models found in the literature are based on fitting of the simple power law equation. In this study, an AZ31B constitutive model that takes into account microstructural evolution is introduced. This model takes into account grain growth and cavity formation in addition to strain and strain rate hardening. The model parameters were calibrated using the results of high temperature bulge forming tests and microstructural analysis. The Taguchi optimization method was used in the fitting process. In order to verify the model, simulations of the superplastic forming of two different geometries were carried out, and the results were compared with those obtained experimentally. Results show that the proposed model can accurately predict the formed geometry and thickness distribution.

Highlights

The ability of certain materials, under certain conditions, to undergo large uniform plastic strains is known as “superplasticity”
The goal here is to form an AZ31B part with a primary and a secondary feature
Complexity in the material behavior, makes constitutive modeling of such materials a hard a constitutive model for AZ31B was established based on a comprehensive numerical-experimental challenge

Summary

Introduction

The ability of certain materials, under certain conditions, to undergo large uniform plastic strains is known as “superplasticity”. This phenomenon had been applied in the manufacturing of the Damascus steels from 300 B.C. to the late nineteenth century [1,2,3]. Magnesium (Mg) alloys have many advantages, such as high specific strength and specific stiffness, excellent thermal conductivity, outstanding shock absorption, and strong electromagnetic shielding. Because of their typical hexagonal close packed crystal structure, they exhibit low ductility at Room Temperature (RT), making their sheet applications greatly limited.

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Conclusion