The effect of Al-5 wt%Ti-0.2 wt%B on the solidification characteristics of 55 wt%Al-Zn-1.6 wt%Si alloy in hot-dip coating

In order to research the mechanism which grain refinement of 55 wt%Al-Zn-1.6 wt%Si alloy by Al-5 wt%Ti-0.2 wt%B (master alloy), the effect of different amount of master alloy on the microstructure and characteristic value of solidification for 55 wt%Al-Zn-1.6 wt%Si alloy were studied using thermal analysis. Important solidification events evaluated using the first and second derivative-cooling curve. The results show that the onset temperature of solidification increased from 560.1 to 572.2 degrees C, namely, the temperature of nucleation for primary alpha-Al increased from 560.1 to 572.2 degrees C after adding master alloy, latent heat of solidification which calculated by Fourier method increased from 16836 to 185.61 KJ and agreed with the result of phase diagram (CALPHAD) calculation. Then, the microstructure and phase composition of cooling samples was analyzed. The results show that the microstructure was composed of primary alpha-Al, binary eutectic of Al-Si, ternary eutectic of Al-Zn-Si and agreed with the thermodynamic calculation. (C) 2016 Elsevier B.V. All rights reserved.