Strain Rate Dependence of Material Strength in AA5xxx Series Aluminum Alloys and Evaluation of Their Constitutive Equation

Hiroyuki Yamada,Ryota Mori,Minemitsu Okada,Tomoyuki Kudo,Tsuyoshi Kami

doi:10.3390/met8080576

Abstract

The effect of strain rate on the mechanical properties of AA5xxx series aluminum alloys containing solute Mg atoms (AA5005, AA5021, AA5082 and AA5182) and pure aluminum (A1070) was investigated within a wide strain rate range of 1.0 × 10−4 to 1.0 × 103 s−1 at room temperature. The A1070 exhibited a positive strain rate dependence of material strength at the investigated strain rates. However, the AA5xxx series aluminum alloys primarily exhibited the negative strain rate dependence of material strength and serration caused by the Portevin-Le Chatelier effect on the Mg content and strain rate. As a result of using the material constitutive equation for the negative strain rate dependence, it was found that the flow stress may change in the dynamic strain rate range. However, it was found that the strain rate dependence of material strength differed in the AA5082 and the AA5182 alloys. It would be caused by less solute Mg of the Al phase in the AA5182 alloy than in the AA5082 alloy, because more Mg2Si compounds precipitated on Mn bearing particles as precipitation sites in the AA5182 alloy.

Highlights

Many constitutive equations have been proposed for the strain rate and temperature effect [1].In these equations, the flow stress is expressed as a function of various parameters, as follows:σ = f ε, n, Y, ε, T (1)where ε is the strain, n is the work hardening rate, Y is the yield stress, ε is the strain rate, and T is the testing temperature
The thermal activation theory became the dominant mechanism because the Mg atoms could not migrate to the dislocation at such high strain rate
We investigated commercial pure aluminum (1070) and commercial aluminum alloys with different Mg content amounts (5005 alloy, 5021 alloy, 5082 alloy, and 5182 alloy) and obtained their tensile properties within a wide strain rate range of 1.0 × 10−4 to 1.0 × 103 s−1 under room temperature

Summary

Introduction

Many constitutive equations have been proposed for the strain rate and temperature effect [1]. In these equations, the flow stress is expressed as a function of various parameters, as follows:. It is necessary to conduct experiments within a wide strain rate range and testing temperature. Experiments have been conducted by using a universal testing machine for the quasi-static strain rate in the range of 10−5 to 10−1 s−1 , and the split Hopkinson pressure (SHB) method [2,3] for the high strain rate. Material properties at the dynamic strain rate in the range of 100 to 101 s−1 have barely been investigated because it is difficult to measure the dynamic tests in principle by using the SHB method. The material properties at those strain rates are important

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Conclusion