Effects of Si_p size and volume fraction on properties of Al/Si_p composites

Al-12 wt.% Si alloy matrix composites reinforced with high volume fraction of Si_p were fabricated by squeeze infiltration. The effects of the compacting pressure on the volume fraction of Si_p in preforms, and the influences of Si_p size and volume fraction on the properties of Al/Si_p composites were examined through this study. Si particles were compacted at different pressure of 40-130 MPa followed by sintered at 1000 °C for 7 h to obtain preforms containing 60-70 volume fraction (vol.%) of Si_p. The sintered preforms were then infiltrated with Al-12 wt.% Si alloy at 750 °C under a 75 MPa squeeze infiltration pressure. It was found that lower coefficient of thermal expansion (CTE) and smaller density may be obtained with higher Si_p volume fraction, yet increasing Si_p volume fraction leads to higher amount of porosities in the composites and thus lowers the thermal conductivity (TC) and flexural strength. Besides, with the same Si_p volume fraction, coarse Si particles result in higher CTE and TC, while finer Si particles may lower CTE and enhance the flexural strength of the composites effectively. From the results obtained in this study, it is expected that the high volume fraction Si_p reinforced Al/Si_p composites posses good potential in electronic packaging applications.