Precipitation kinetics in Al-Si-Mg/TiB₂ in-situ composites

Abstract

Al-7Si-0.3Mg-TiB₂ in-situ composites were made by the salt-metal reaction i.e., the reaction of K₂TiF₆ and KBF₄ salts with the molten alloy. The kinetics of the formation of intermediate metastable precipitates in the process of Mg₂Si formation in Al-7Si-0.3Mg-TiB₂ in-situ composites with three different amounts of TiB₂ particles (2.5, 5 and 10 wt.%) were studied using differential scanning calorimeter (DSC) and also compared with the Al-7Si-0.3Mg base alloy. Kissinger analysis of non-isothermal DSC scans at various heating rates was carried out to evaluate the activation energies associated with the precipitation processes. The metastable precipitates were characterized by taking the solutionized samples to their respective DSC peak temperatures at a particular heating rate and the samples were then observed under a transmission electron microscopy. It was found that there is a decrease in the activation energies of the GP zones with increase in TiB₂ content.