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

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.

Effects of Pulsed Magnetic Fields of Different Intensities on Dislocation Density, Residual Stress, and Hardness of Cr4Mo4V Steel

“…The result is that the covalent bond is much easier to break. The atomic mobility is enhanced and the atom-migration-related processes are prompted [34]. Thus, the mobility of vacancy or impurity atoms increases so that the dislocation depinning could occur under the original stress field and leads to the dislocation movement.…”

“…This vibration provides energy for the dislocation movement. It should be emphasized that the thermal energy induced by a magnetic field with an intensity of several Teslas is ignorable [34]. As the total processing time is only 55 s, the temperature of the Cr4Mo4V steel sample hardly changes.…”

Effect of P10 Cemented Carbide Cutting Tools Subjected to Electromagnetic Coupling Field Treatment on the Surface Roughness of Machined 45 Steel

“…We note that the peak values of the EPR spectra increased by 7.28% at the signal crest and 29% at the signal trough after EMCFP treatment. Magnetic eld can increase the number of unpaired electrons which can change the state of free radical form (Singlet) S to (Triplet) T [7,19]. The combine energy of electron pair is strong in S state, but weak in T state.…”

“…Under the combined impacts of the electro-plastic effect [21,22] and the magnetostriction effect [23], the EMCFP treatment increased dislocation mobility by decreasing the activation energy of dislocation movement, which promoted internal stress release. In addition, the EMCFP process provides the necessary energy for dislocation motions to occur, resulting in the homogenization of the dislocation distribution in the material [7]. Simultaneously, applied electric elds reduce entanglement between dislocations, which removes obstacles toward dislocation slippage, so that the material exhibits higher plasticity [24].…”

“…The results indicated that the optimum magnetic eld enhanced coating properties, resulting in a reduced friction coe cient and increased wear resistance. Zhang et al [7] applied a magnetic eld during the processing of a titanium alloy, and the tensile stress was observed to be decreased by 24% owing to the homogenization of the residual stress via the excitation of dislocation relaxations by the magnetic eld. Xu et al [8] investigated the in uence of pulsed magnetic eld treatment on the microstructure of TC4 titanium alloy.…”