Research on precipitation of second phases for Al-Ti-B master alloy refiner

An Al-Ti-B master alloy was prepared by the reaction of complex halide salts with molten aluminum at high temperature and the thermodynamics principle was analyzed. The effect of extrusion process on microstructure was studied by comparing the microstructure after squeezing with the as-cast microstructure. It is found that TiAl₃ blocks become smaller and smoother after extrusion, and recrystallization happens when squeezing, which results in homogeneous distribution of TiB₂ particles. Besides, the precipitation of TiAl₃ and TiB₂ in aluminum melt was investigated by stewing experiment and the factors affecting deposition were described. The methods to slow or impede precipitation of second-phase particles were put forward, and the optimized extrusion process and the addition of proper rare earth were emphasized.