Study On Ti-Mg System Alloys By Spark Plasma Sintering Method

Titanium alloys are widely used in aerospace applications because of their high strength to weight ratio and good corrosion resistance. Reducing density is the most effective way of reducing the weight of structural components and for Ti alloys this could be done by alloying with light elements such as Mg. Magnesium alloys are attractive materials in aerospace and automobile industries mainly because of their low densities and high specific resistance. Nevertheless, their use has been limited because of their poor corrosion resistance and mechanical properties. It has been observed that this resistance and properties can be improved by alloying with titanium. Therefore, Ti-Mg system alloys have synthesized by spark plasma sintering method in this paper. And their microstructure and performance have been studied.Ti-Mg alloys and Mg-Ti alloys are obtained under the sintering technical condition of 1080 C-10MPa-10min and 540 C-10MPa-10min respectively using an SPS apparatus (Dr. SINTER, SPS-1050, Sumitomo Coal Mining Co. Ltd., Japan). A constant heating rate of 100掳C/min is employed, while the applied pressure is lOMPa.The phase compositions and microstructures of Ti-Mg system alloys are mainly investigated by XRD, optical microscope, SEM and EPMA analysis. It is found that the Ti-Mg alloys are composed of a-Ti and a small quantity of MgO and TiN2. With the increasing of Mg content, -Ti appears in samples. It is because that Mg is easier to vaporize and oxidate at high temperature, subsequently there are a lot of fine pores and a small quantity of MgO existing the wall of the pores. At the same time, Ti begins to react with N2 and comes into being a bit of TijN.While Mg-Ti alloys mainly include a-Ti and Mg, its can be seen as a simple mixture system. It doesn't occur any reaction between Mg and Ti. Mg fills between Ti grains and pores, which is good at fluidity at 540 C. As a result, Mg-Ti alloys will reach high density.Subsequently, the ideal mixture model is adopted to estimate the densities, volume velocities and specific heats of Mg-Ti alloys. Relative research indicates that not only the compositions but also microstructures of the composites affect theirphysical properties.Finally, by employing mechanical properties test, it shows that the tension strength, elastic modulus and micro-hardness of Mg-Ti alloys have increased evidently with joining Ti due to the high tension strength and melting point as well as high elastic modulus of Ti. However, the tension strength will decrease when the mass fraction of Ti is overmuch. At the same time, the ductility of Mg-Ti alloy will decrease with joining of Ti.