Research On Microstructures Of Magnesium Alloys Heat Treated Under High Magnetic Fields And The Preparation Of Mg-Ti Thin Films

As an important branch of electromagnetic processing of materials, the application of high magnetic fields has attracted widespread attention in recent years, especially on the study of the solidification process of alloys and the preparation of grain-oriented materials under magnetic fields. High magnetic fields heat treatment, as a novel heat treatment method, mainly takes advantage of the differences of magnetization energy between different compositions or solute elements during the solid-state phase transformations, thereby changing the process and effectiveness. This paper introduced a10T high magnetic field in the heat treatment process of Mg-Gd-Y-Zn-Zr alloys. The Mg-9Gd-3Y-0.6Zn-0.5Zr (wt.%) alloy and the Mg-8Gd-5Y-2Zn-0.5Zr (wt.%) alloy were heat treated respectively under0T and10T. And their microstructures were analyzed to research the effect of high magnetic fields heat treatment on the microstructures and grain orientation of the alloys. The results show that:(1) High magnetic fields heat treatment induces the preferred grain orientation of the a-Mg matrix, while it may have a weak influence on the alignment of the LPSO phase. Due to the high grain boundary migration rate in the process of heat treatment, a driving force will effect on the grain boundary migration with the addition of high magnetic fields, which makes the c-axis of a-Mg grain aligned perpendicular to the direction of the high magnetic fields.(2) High magnetic fields heat treatment can promote the formation of the long period stacking ordered structure (LPSO) phases. During the process of heat treatment under high magnetic fields, the magnetization energy originates from the differences of solute element contents between the grain boundaries and interiors. It may provide a driving force to make the solute elements diffuse from the grain boundaries to the grain interiors. Thus, it contributes to the formation of the LPSO phase and the growth from the grain boundaries to the interiors.Magnesium-based hydrogen storage films have been a hot spot with its low density, large surface area and high hydrogen storage capacity. The performances of films can be greatly improved if films have a specific texture, which may be controlled by high magnetic fields. The second part of this paper mainly prepares films for the study of the effect of the high magnetic fields heat treatment on the texture of films. Mg-Ti films were prepared by magnetron sputtering method. And the analysis of the microstructures of the films shows that:(1) The composition of the MgxTi1-x films is mainly associated with the sputtering power of targets. When the sputtering power ratio of the Mg and Ti targets is7:11, the composition of the films is Mg80Ti20.And the thin film will present a porous morphology on its surface, which may improve the hydrogen storage performance.(2) Sputtering pressure can significantly affect the cross-section morphology of the multiple films. When the sputtering power ratio is7:11and the sputtering pressure is0.3Pa, the Mg80Ti20/Mg multilayer films will have clear demarcation between layers.