Study on interfacial thermal stability of SiCf/TC25G composites
The prolonged exposure of TMCs to high temperatures results in severe interfacial reactions between the matrix and the fiber,leading to a degradation in the mechanical properties of the compos-ites.In this study,SiCf/TC25G composites were prepared using a magnetron sputtering precursor wire method followed by hot isostatic pressing process.The interface reaction and thermal stability of the composites were investigated.Specifically designed interfacial thermal stability experiments under dif-ferent thermal exposure conditions were conducted based on the service temperature of TC25G titani-um alloy.The resulting interfacial morphology and products of the composites under hot isostatic pres-sure and hot exposure were analyzed using various techniques including SEM,TEM,EPMA,XRD,and EBSD techniques.The primary product of the interface reaction layer in SiCf/TC25G composites under hot isostatic pressure is validated as TiC,and the silicides in the reaction layer near the matrix side and the matrix precipitate in the form of(Ti,Zr)6Si3.As thermal exposure temperature and holding time in-creased,both the thickness of the interface reaction layer increases while that of the C coating decreases.Based on these observations,a growth law for SiCf/TC25G composite was summarized.The activation energy for the growth of the interfacial reaction layer in SiCf/TC25G composites is 50.53 kJ/mol,and the exponential factor for the reaction layer growth is 1.23×10-7 m/s12.