Fabrication of controlled expansion Al-Si composites by pressureless and spark plasma sintering

A combination of low coefficient of thermal expansion (CTE) and decent thermal conductivity (TC) is the reason for the Al-high vol% Si system to become popular for electronic packaging material. In the present work, two process routes, firstly conventional powder metallurgy and then spark plasma sintering (SPS) were utilized for the fabrication of Al-20-60 wt.% Si composites. In addition, effect of small fraction of CNT addition on the CTE of Al-20 wt% Si was studied. Effect of process parameters on the consolidation of the composites in terms of densification, microstructure evolution along with fractographic analysis and strength was studied. CTE and TC of the sintered composites were measured and correlated with the densification, percentage of Si and morphologies of the sintered products. Overall, better densification could be achieved in SPS and the Al-30% Si and Al-40% Si composites SPSed at 550 degrees C showed average CTE values of 14.52 x 10 (6)/K and 13.36 x 10 (6)/K, respectively, in the temperature range of 30-200 degrees C, which were better than some of the existing alloys with higher Si content. Simultaneously, TC values were 114.4 W/mK and 107.12 W/mK, respectively, for the above two SPSed composites. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.