The Research About Grain Refining Property And Preparation Of Al-Ti-B Master Alloy

The process of preparation about Al-Ti-B master alloy grain refiner was studied by means of orthogonal test and single one. Al-Ti-B master alloy of different ratio of Ti and B was produced. In the various condition of solidification and remeltment, variational laws about pattern, size and distribution of the second phase were attained. The refining specialities of Al-Ti-B master alloy refiner were researched, the comparison to refining effect of refiner self-produced, inland refiner and import one were analysed by the refining test of pure aluminum.The effects and the influenced degree of superheating temperature of aluminum melt, The methods of addition, the time of reaction, holding time, casting temperature, thickness of overlay and stirring on the morphology, size, distribution of the second phases in the Al-Ti-B master alloy preparated were discussed in the preparation test. The results indicated superheating temperature of melt was the major factor, the other factors were the ordinary ones. Mixed addition and casting of middle and low temperature(about 800C),It can improve the absorbing rate of boron. Stirring, superheating temperature and casting temperature had affected morphology, sizes and distribution of Al-Ti-B master alloy.Variational laws of Al-Ti-B master alloys morphology were discussed: in the common solidification condition, with the improvement of remelting temperature, the size of small block-like TiAl3 become larger and the number of ones become smaller, variational tendency of bulky needle and flak-like appeared reverse change. While the morphology of TiB2 hardly was affected in the condition of superheating, the size of TiAl3 would become small and the distribution of TiB2 would become more even with the hoisting of superheating temperature in the condition of rush solidification.Forming mechanism and thermal conditions about the second phases of Al-Ti-B master alloy in the different addition methods were analysed by the thermal theory of melt reaction and experimental methods (SEM, XRD and EMPA), meantime dynamics mould was come up with three kinds of addition methods.The optimum additional quantity, the optimum contacting temperature and the optimum contacting time of Al-Ti-B were researched in the condition of grain refining test of pure aluminum. The result indicated that 0.2 percent of aluminum melt weight was the optimum additional quantity, the optimum contacting temperature was about 700C-750C, grain refining effect was good when the holding time of melt was 2 to 30 minute, but with the extending of holding time, the grain refining effect declined. The tensile strength of pure aluminum refined increased by 62.65% and elongation of pure aluminum refined increased by 131.11 %, the refining ability of Al-Ti-B master alloy of self-made touched the ones of import grain refiner. The grain refining mechanism of Al-Ti-B master alloy was discussedelementarily by analyse about nucleus of pure aluminum and the existing theories.