Effects of Holding Conditions on Microstructure of Al-5Ti-1B and Its Refining Efficiency on Al-Cu Alloy

A series of Al-5Ti-1B master alloys were obtained via fluoride salt process by holding them between 780°C and 880°C for 10-90 min. The influence of holding temperature and time during preparation on the microstructure and its refining performance were investigated by X-ray diffractometer, optical microscopy and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The results indicated both the morphology and the distribution of TiB2₂and Al₃Ti were seriously affected by holding conditions. Inadequate TiB₂ particles were generated when holding time was short. However, Fe-containing impurity particles that aggregated along the matrix grain boundaries were found after the prolonged holding time. The refining and microhardness test results revealed that Al-5Ti-1B, the one held at 820°C for 30 min showed the optimum refining efficiency on Al-Cu alloy.