Thermal analysis of in-situ Al 2 O 3 /SiO 2(p) /Al composites fabricated by stir casting process

• DOI: 10.1016/j.tca.2016.08.009
• Publication Date: 2016-08-25T22:23:28Z
• Authors: Kang Wang; Wenfang Li; Jun Du; Lu Yang; Peng Tang
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract The in-situ fabricated Al 2 O 3 /SiO 2(p) /Al composites were produced by adding different quantities of SiO 2 particles (viz. 0, 3, 6 and 9 wt.%) into molten commercial purity Al at 750 °C. Newtonian thermal analysis was conducted to investigate the solidification behaviors of these molten composites prepared by the stir casting process. The microstructure and phase identification were achieved via optical microscope, SEM (equipped with EDS) and X-ray diffraction. Results showed the dendrite arm spacing of α-Al grain decreased with the increase of SiO 2 addition. The SEM image showed the special duplex phase with Al 2 O 3 layer formed around SiO 2 particle in Al matrix. The Si concentration in Al matrix increased with increasing in the SiO 2 addition, resulting in the decrease of liquidus temperature of the melts. Compared with the purity Al melt, one more stage related to the exothermic Al-Si phase transformation was revealed in the cooling curves of these molten composites. Cooling rate of the purity Al melt was lower than that of the melts with SiO 2 particles addition. The difference in solidification behaviors of these melts was ascribed to the effect of SiO 2 /Al reaction on the effective heat capacity and different amounts of latent heat released from phase transformation process.