A Study On Al-Ti-C Grain Refiner Fabricated By SHS Technology

Compared with conventional Al-Ti-B master alloy, Al-Ti-C grain refiner has little limitations existed in Al-Ti-B master alloy. For example, Al-Ti-B grain refiner has the larger TiB2 particles. In addition, TiB2 particles also tend to be poisoned by elements Zr, Cr or Mn in aluminum melt and to lose their refining effectiveness. Therefore, it has been generally accepted that Al-Ti-C master alloys with TiC particles are considered to be the most promising grain refiner for aluminum and its alloys, But because of poor wettability of carbon with molten aluminum, the grain refiner can not been fabricated steadily by the way of ecumenical melting. Studying new preparation technology of the grain refiner is always the seeking target by people. In order to reach the target, the paper puts forward a new technics of fabricating the grain refiner -Self-propagating high-temperature synthesis (SHS) technology. The reaction energetics of Al-Ti-C system have been theoretically analyzed and calculated based on solution thermodynamic theory at first. The results indicate: Al-Ti-C perform dipped into the melt can be ignited the combustion synthesis reaction by the inherent heat of an elevated temperature Al-melt. And can gain needed Al3Ti and TiC of grain refiner. Fabricating Al-Ti-C master alloys grain refiners based on self-propagating high-temperatuer synthesis (SHS) technology in molten Al is promising. Al-Ti-C grain refiners have been fabricated by the direct self-propagating high-temperature synthesis (SHS) technology and self-propagating high-temperatuer synthesis (SHS) technology in molten Al. The effects of the temperature of the melt and the composition of the mixture on the microstructrues of the fabricated master alloys were studied systemically. The research results indicate that Al-Ti-C grain refiners synthesized directly by SHS technology consist of Al matrix and submicron-sized TiC particles, whereas the grain refiners fabricated by SHS in molten Al contain three phases of Al, Al3Ti and TiC. The refining performances for commercially pure aluminum and resistance to grain refining fading of the Al-Ti-C master alloys fabricated respectively by above two techniques have been compared by refining experiments. The refining experiments indicate the grain refiners fabricated respectively by above two techniques exhibit excellent grain-refining performances for commercially pure aluminum and high resistance to grain refining fading. However, in view of production cost and technical features of the grain refiners, it is found that SHS technique in molten Al is more suitable for the industry producing of the grain refiners.