Preparation and Characterization of Al-B and B-Rich Al-Ti-B Master Alloys for the Grain Refinement of Al-7Si Alloy

摘要

The present paper reports on the preparation and characterization of Al-B and B-rich Al-Ti -B master alloys and their performance in the grain refinement of Al-7Si alloy. The grain refining efficiency of Al-7Si alloys has been studied in detail with these indigenously prepared binary (Al-Ti, Al-B) master alloys with conventional as well as higher addition levels. Binary Al-3B and ternary Al-1 Ti-3B master alloys have been made by the reaction of halide salts (K_2TiF_6 and KBF_4) with molten Al. A number of master alloys have been prepared by varying the process parameters such as reaction temperature and reaction time. After optimizing the reaction temperature and time various binary Al-3Ti, Al-3, 5, 7B and ternary Al-3Ti-1B, Al-1Ti-3B, Al-5Ti-1B and Al-1Ti-5B master alloys have been prepared and characterized by chemical analysis, particle size analysis, XRD and SEM/EDX microanalysis. The present results suggest that, a minimum of reaction time of 60min was found to be essential in order to reach the completion of the reaction within the experimental conditions studied in the present investigation. Similarly, the optimum reaction temperature was found to be 800 deg C. Results also suggest that, the reaction between molten Al and K_2TiF_6 is quite intense and as a result high Ti recovery with large Al_3Ti particles within the reaction time studied at a reaction temperature of 800 deg C. Under similar conditions the reaction of molten Al and KBF_4 is rather sluggish and is more so in presence of K_2TiF_6 and results in low B recovery and formation of comparatively small AlB_2/AlB_12 particles. In addition, the present results suggest that, high B containing (Al-3B and Al-1Ti-3B) master alloys are more efficient grain refiners for Al-7Si alloy, both at short and long holding times, when compared to conventional grain refiners (Al-5Ti-1B) and high Ti containing (Al-3Ti and Al-3Ti-1B) master alloys.