Preparation and Performance of SiC Foam Ceramic/Fe Matrix Co-continuous Phase Composites

Abstract

SiC foam ceramic/Fe based co-continuous phase composites were prepared by squeeze casting method using oxidized SiC foam ceramic.Then the prepared composites were annealed.The influence of preparation process and SiC volume fraction on microstructures and mechanical properties of the composites were investigated.Results show that a SiO2 barrier film of 1 mm in thickness on the surfaces of SiC foam can form after oxidizing at 1250°C for 48 h,which then can efficiently prevent the formation of a brittle intermetallic compound Fe3 Si at the interface of Fe matrix and SiC during the preparation of composites.As a result,the flexural strength of composites was increased by 100% and compressive strength by 18%.The thickness of SiO2 film was increased after oxidizing at 1250°C for 72 h,and a thicker SiO2 film may induce mismatch of thermal expansion coefficient between SiO2,Fe and SiC,which thereby resulted in the increase of residual stress.Therefore,the mechanical properties of composites were decreased slightly.The residual stress could be relieved after annealing of composites at 600°C for4 h,which improved the mechanical properties of composites.The function of bridging and deflecting crack of metal matrix is big for the composite with small SiC volume fraction,which is in turn beneficial to the enhancement of the flexural strength and flexural strain.For the composite with the higher SiC volume fraction,the size of SiC skeleton became bigger and the load- carrying capacity was strengthened,thereby its compressive strength was increased.