Effects of Magnetic Field on the Residual Stress and Structural Defects of Ti-6Al-4V

Xu Zhang,Jiluan Pan,Qian Zhao,Zhipeng Cai

doi:10.3390/met10010141

Abstract

In this work, the influences of a magnetic field of 2.4 T on the macro residual stress and the status of structural defects, including grain boundaries, dislocations and the Fe-rich clusters of Ti-6Al-4V were investigated by X-ray Diffraction (XRD), Electron Backscatter Diffraction (EBSD) and magnetic measurement. The XRD test results show that the applied magnetic field can cause the relaxation and homogenization of macro residual stress. The maps of Kernel Average Misorientation (KAM) values obtained by EBSD tests present a significant dislocation multiplication caused by a magnetic field, and the rise of dislocation density was estimated to be about 32% by XRD tests. The EBSD test results also show an increase in the fraction of Coincidence Site Lattice (CSL) grain boundaries and a decrease in the fraction of low-angle grain boundaries. The results of magnetic measurement show that Ti-6Al-4V has mixed magnetism consisting of paramagnetism and weak ferromagnetism, and that the ferromagnetic saturation magnetization decreased after exposing the alloy to the magnetic field, which suggests the dissolution of the Fe-rich clusters in the alloy. These magnetically-induced changes are related to magnetoplastic effects, a kind of phenomena on which there have been some research, and the possible mechanism of them is discussed in this paper.

Highlights

Ti-6Al-4V is the most widely used titanium alloy in aerospace, biomedicine and the petrochemical industry because of its excellent performance, such as high specific strength, fine corrosion resistance, outstanding tissue compatibility and good weldability [1,2,3,4], and various advanced technologies to further enhance its performances have attracted increasing attention [5,6,7]
As a result of the changes that take place under the magnetic field, besides the simultaneous effects, there are residual effects which will remain after switching off the field [9,18,19,21]
Scanning Electron Microscope (SEM) micrographs of the alloy are shown in Figure 1a,b, from which we can see that the SEMdistributes micrographs of Distribution the the alloyα are in chemical

Summary

Introduction

Ti-6Al-4V is the most widely used titanium alloy in aerospace, biomedicine and the petrochemical industry because of its excellent performance, such as high specific strength, fine corrosion resistance, outstanding tissue compatibility and good weldability [1,2,3,4], and various advanced technologies to further enhance its performances have attracted increasing attention [5,6,7]. Magnetoplastic effects refer to the phenomena that the mobility of dislocations in materials and the macro plasticity of materials increase in a magnetic field. With the development of the relevant research, various influences of a magnetic field on the mechanical properties and the status of the structural defects of materials are all usually referred to as magnetoplastic effects [9,20]. As a result of the changes that take place under the magnetic field, besides the simultaneous effects, there are residual effects which will remain after switching off the field [9,18,19,21] This is a potential method worth exploring to improve the service behavior of Ti-6Al-4V using magnetic field

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Conclusion