Evaluation of the effect of grain refiners on the solidification characteristics of an Sr-modified ADC12 die-casting alloy by cooling curve thermal analysis

Abstract

The influence of grain refinement - with the addition of 6 mass% Al-5Ti-B and 10 mass% Al-3Ti-B master alloys - on the temperature-based parameters of a commercial ADC12 die-casting alloy, modified with 0.04 mass% Sr, was investigated using computer-aided cooling curve thermal analysis. Results show that the addition of grain refiners caused the reaction area of the aluminium dendrite to shift up. With the addition of refiner reagents, the nucleation temperature and growth temperature for the evolution of the primary Al dendrite increased, while the recalescence temperature decreased. The dendrite coherency temperature (T DCP), time (t DCP), temperature (T N-T DCP), and time (t N-t DCP) interval for dendrite coherency and solid fraction at coherency point increased with the addition of Al-3Ti-B and Al-5Ti-B grain refiners. Nevertheless, the growth temperature of the eutectic aluminium-silicon phase remained at the modified range (563.5-565 °C) even after the addition of grain refiners. A grain-refined and modified structure was obtained after the addition of refiners, but no obvious mutual effect was found in terms of the coarsening of grain size or silicon demodification in the range of concentrations used in this study