In-situ synthesis of SiC particles by the structural evolution of TiC_x in Al-Si melt

摘要

A facile method has been developed to in-situ synthesize SiC particles utilizing the structural instability and evolution of TiC_x in Al-Si melt. It is considered that the synthesis of SiC particles occurs via the gradual reaction between TiC_x and Si atoms, whilst Si content plays the crucial role in this approach. If the Si content in the melt is above 30%, TiQ, directly reacts with Si and Al to form SiC, but the needle-like TiAl_xSi_y phase formed simultaneously will do harm to the mechanical properties of the composites. Thus, it is proposed to add B element in the melt to transform the TLAl_xSi_y into TiB_2 particles. Therefore, the SiC and (SiC + TiB_2) hybrid-particles reinforced Al-18Si composites were successfully prepared using the method. In the composites, the SiC particles have the size range from 2.5 to 7.5 μm and a block-like morphology. Furthermore, the mechanical properties of base alloy, including the wear resistance and macro-hardness, have been obviously improved by the in-situ SiC particles. Besides, the relevant underlying mechanisms are also discussed.