Papers by Keyword: Al-Ti-C Grain Refiner

Abstract: The application of ultrasonic field in the preparation of Al-Ti-C refiners can lead to the the homogenous distribution of the second phase TiAl₃ and the particle phase TiC in the matrix, thus enhancing the refinement effect. In this paper, the Al-Ti-C grain refiner was successfully prepared by the ultrasonic coupling method, and its microstructure was observed. The prepared refiner was added to pure Al to verify the refining performance, and the refining mechanism was analyzed. The results indicate that the Al-Ti-C grain refiner prepared by ultrasonic field has excellent refining performance, which reduces the grain size of Al to 100 μm, and the optimum activation refining time is 3 min. The reason is that the morphology and size of the second phase TiAl₃ and TiC in Al-Ti-C are changed by cavitation effect, acoustic streaming effect and thermal effect caused by high intensity ultrasonic, and the α-Al nucleates effectively under the synergistic of TiC and TiAl₃ particles.

Abstract: SHS technique and conventional melting and casting technology were combined and used for the preparation of Al-Ti-C grain refiner alloy. Experimental results show that when SHS reaction occurs to the Al, Ti and C powder reactant in Al melt and the composition proportion factor, n , is between 4 and 10, the effect of composition on the initial temperature of SHS reaction is small and its initial temperature ranges from 810 to 815°C. However, the highest temperature of the melt increases with increasing n values and increases gradually from 845 to 1370°C. In the meantime, when the composition proportion factor for Al, Ti and C powder reactant, n, is greater than 5.95, its adiabatic temperature Td>1800K which conforms to the empirical criterion proposed by Merzhanov et al. The SHS reaction of reactant can accomplish by self-maintenance.

Abstract: The microstructural characters and refining property of Al-Ti-C grain refinement alloy prepared by ultrasound coupling method were studied by analytical means such as SEM, and the reaction synthesis mechanism of Al-Ti-C grain refinement was discussed. Experimental results show that the Al-Ti-C alloy refiner using “thermite reduction method” under high-energy ultrasound was prepared experimentally. Its microstructure character is that master alloy has smaller size of TiC, its quantities are larger and are dispersed. Melt reaction is generally that the source of titanium releases Ti atoms under high temperature of ultrasonic. Ti atoms react with aluminum to generate TiAl3, and react with carbon to generate TiC.

Abstract: Al-Ti-C grain refiners have been prepared by combining self-propagating high-temperature synthesis (SHS) technique and melting-casting method. Effects of Al powder size and C/Ti ratio on the microstructures and grain-refining efficiency of Al-Ti-C grain refiners were studied by OM, XRD, SEM and EDS. The results show that when Al powder size is fine, and C/Ti ratio is 1: 8, SHS reaction among the mixed powders can easily carry on in the melt. As a result, the prepared grain refiner consists of blocky Al3Ti and fine TiC particles distributed in Al matrix, and exhibits excellent grain refining performance on commercially pure Al.