| The silicon carbide-aluminum(AlSiC)composites has high thermal conductivity(TC)and low coefficient of thermal expansion(CTE),but it is difficult to be machined and welded.The content of silicon carbide(SiC)was carried out gradient in the AlSiC composites.The SiC parts with high content can satisfy the thermal matching requirements in packaging applications,and the parts with low content can improves weldability.Therefore,the research and development of AlSiC functionally graded composites is of great significance.This paper attempts to layer the mixed powder with different SiC content.Then,AlSiC composits with SiC content gradient is prepared by hot squeeze at semi-solid temperature of aluminum alloy.Firstly,the structure and properties of AlSiC composites with high volume fraction of SiC particles were studied.7?m Si powder,20?m Al powder and SiC powder were selected as experimental materials,and the hot squeeze was carried out at600?-650?.Five kinds of AlSiC composites with high volume fraction of SiC particles were prepared,named after Al-7Si+(W14,W63,F240,F240:W14=2:1,W63:W14=2:1)SiC respectively.By adjusting the particle size and composition of SiC,the CTE of AlSiC composites is adjusted from 8.0×10-6/?to 10.0×10-6/?,and it will decrease when the volume fraction of SiC particles increases.The Change of flexural strength in the range of 259?432 Mpa.The fluctuation range of TC is between 188W/m K and 218 W/m K.20?m Al powder,7?m Si powder and 20?m SiC powder were selected as experimental materials.By adjusting the content of SiC in the mixed powder,four kinds of Al-based materials with volume fraction of 0%,10%,20%and 30%SiC were prepared by semi-solid squeeze.SiC particles distribute uniformly at macro scale,but occur segregation at micro scale.This is due to the SiC particles be extrapolated to post-solidified aluminium liquid with rich content of Si by separated out?-Al particles from composites during semi-solid sample cooling.And it resides in the final solidified Al-Si eutectic zone with network structure.The flexural strength and TC increase with the increase of SiC particle content.The CTE decreases with the increase of SiC content and fluctuates between 14.0×10-6/?and 21.0×10-6/?.Lastly,four-layer graded AlSiC composites were prepared by semi-solid hot suqeeze,which use the method of laying powder by layers.The interface between layers is in good contact and SiC particles are distributed uniformly in the layers.The interlayer infiltration of liquid aluminium alloy occurs in the process of simultaneous densification,which results in the increase of SiC content in the intermediate transition layer and a slight decrease in CTE. |
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