Superplastic Flow and Deformation Mechanism of the Rolled Al-Mg-Li-Sc-Zr Alloy with Banded Microstructure

Chengzhi Zhang,Zhipeng Liu,Zhenjie Liu,Yang Xiao,Kaijie Ma,Wenjing Zhang,Yuhan Wang

doi:10.3390/met11030404

Chengzhi Zhang, Zhipeng Liu + Show 5 more

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https://doi.org/10.3390/met11030404

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Abstract

A hot rolled Al-5Mg-2Li-0.2Sc-0.12Zr alloy sheet with an initial banded microstructure was subjected to high-temperature tensile tests in the temperature range of 450–550 °C, at strain rates ranging from 3 × 10−4 to 1 × 10−2 s−1. The microstructural evolution of the present non-ideal superplastic microstructure (banded morphology) was characterized by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the hot rolled non-ideal superplastic microstructure exhibited excellent superplasticity. The optimal superplastic forming temperature appeared at 500 °C and the largest elongation of 1180% was achieved at 500 °C and 1 × 10−3 s−1. As far as we know, this is the largest elongation for Al-Mg-Li-Sc-Zr alloys. The superplastic deformation of the present hot rolled banded microstructure can be divided into two stages: (i) dynamic globularization due to the dislocation movement and continuous dynamic recrystallization (CDRX), which is responsible for the plastic deformation in the low strain range; (ii) superplastic flow of the spheroidized equiaxed grains with a high ratio of high-angle grain boundaries (HAGBs) and random grain orientation in the high strain range, during which grain boundary sliding (GBS) plays the dominant role in influencing the superplastic deformation.

Highlights

The results show that the m values of the present hot rolled Al-Mg-Li-Sc-Zr alloy are between 0.31 and 0.57 and the average m value is 0.49
The results show that the m values of the present hot rolled Al-Mg-Li-Sc-Zr alloy are between 0.31 and 0.57 and the average m value is subjected heat,mwhereas the gauge is affected heat and strain
Because of the Sc element added to the alloy, the hard phase containing the Sc element formed, which can be proved by the energy disperse spectroscopy (EDS) analysis

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The Al-Mg-Li alloy, as a structural material, has been widely used in the field of aerospace owing to it having the advantages of a low density, high specific strength, good welding performance and excellent corrosion resistance [1,2]. It is difficult to manufacture the complex-shaped thin-walled parts using conventional processing methods because of their poor formability, high notch sensitivity, large spring-back and easy cracking during plastic deformation at room temperature [3,4,5]. Superplastic forming (SPF), as a near-net forming method, works as one of the effective methods to solve this problem and can be used to fabricate the complex-shaped structural components of the

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