Constitutive Equation and Hot Compression Deformation Behavior of Homogenized Al-7.5Zn-1.5Mg-0.2Cu-0.2Zr Alloy.

Weiweng Zhang,Wen Zhang,Jianliang He,Datong Zhang,Cheng Qiu

doi:10.3390/ma10101193

Abstract

The deformation behavior of homogenized Al–7.5Zn–1.5Mg–0.2Cu–0.2Zr alloy has been studied by a set of isothermal hot compression tests, which were carried out over the temperature ranging from 350 °C to 450 °C and the strain rate ranging from 0.001 s−1 to 10 s−1 on Gleeble-3500 thermal simulation machine. The associated microstructure was studied using electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results showed that the flow stress is sensitive to strain rate and deformation temperature. The shape of true stress-strain curves obtained at a low strain rate (≤0.1 s−1) conditions shows the characteristic of dynamic recrystallization (DRX). Two Arrhenius-typed constitutive equation without and with strain compensation were established based on the true stress-strain curves. Constitutive equation with strain compensation has more precise predictability. The main softening mechanism of the studied alloy is dynamic recovery (DRV) accompanied with DRX, particularly at deformation conditions, with low Zener-Holloman parameters.

Highlights

7000 series Al–Zn–Mg–Cu alloys have a combination of high strength-to-density ratio, high hardness, and good resistance to stress corrosion, which have been widely used as structure materials in automotive and aerospace industries [1,2,3]
It can be found that the strain rate and deformation temperature have great influence on the flow stress level
The flow stress increases with increasing strain rate or decreasing deformation temperature

Summary

Introduction

7000 series Al–Zn–Mg–Cu alloys have a combination of high strength-to-density ratio, high hardness, and good resistance to stress corrosion, which have been widely used as structure materials in automotive and aerospace industries [1,2,3]. In order to reduce CO2 emission, light-weight cars have drawn great interests around the world. Application of high-strength aluminum alloys is an important way to reduce the weight of automobile. The limited workability is one of the main obstacles for extensive application of high-strength 7000 series alloys. With the contents of alloying elements increasing, the strength of 7000 series alloys increase, and the workability turn worse. To improve the workability and plasticity of these alloys, methods such as composition optimization, grain refinement, and deformation processing optimization, etc., can be used

Methods

Results

Conclusion