The Preparation And Refining Performance Research Of Al-Ti-C Master Alloys

Al-Ti-C grain refiner was prepared by a new craft in which the aluminum liquid adding into the mixture of graphite and K2TiF6 in medium frequency inductance furnace. The refining effects of Al-Ti-C grain refiner were examined by adding it into pure aluminum. Al-Ti-C grain refiner has the most potential in the field of aluminum and aluminum alloys refining, and has the important significance for enhancing the quality of aluminum and aluminum alloys casting.By some testing methods, such as OM,SEM-EDS,EPMA etc,the influences of choice of carbon sources,ways to add graphite,reactive temperature and holding temperature on chemical composition and microstructure of Al-Ti-C master refiner were studied; In the experiment to check the refining effects on pure Aluminum, the Ti/C ratio,additional magnitude,holding time and casting temperature were studied during the preparation of Al-Ti-C master refiner. The comparison of refining effects was made between Al-Ti-C grain refiner and Al-Ti-B grain refiner produced in England or domestic. The results showed that, when the stuff added at 850℃and the holding temperature at 1100℃for 10 minutes, the Al-Ti-C grain refiner made by this craft has a prime performance and it's refining effects on pure aluminum was better than Al-Ti-B grain refiner produced in England or domestic.The Al-Ti-C master alloys of several compositions and different Ti/C ratio were prepared by the craft, such as Al-6Ti, Al-5Ti-0.25C, Al-5Ti-0.02C, Al-8Ti-2C, Al-8Ti -0.4C, Al-12Ti-0.45C etc. The reactive mechanism of TiC and TiAl₃ phases in preparation were studied and the thermodynamic conditions of the compounds were analyzed. Additionally, the growth kinetic model of TiC was proposed. Moreover, Al-Ti-C ternary phase was studied and the heterogeneous nucleus mechanism forα-Al was investigated. The research results showed that, flake-shape TiAl3 and fine TiC particles were found in casting structure of Al-Ti-C master alloys and most TiC particles distributed homogeneously in substrate.Through the preparation experiment and refinement experiment, singular TiC and TiAl₃ can only play limited role, the joint of TiC and TiAl₃ was the essential condition to realize the pure aluminum refined effectively when aluminum and alum- inum alloys were refined by Al-Ti-C master alloys .