SiC_f/TC17复合材料界面热稳定性及元素扩散机理

THE INTERFACIAL THERMAL STABILITY AND ELEMENT DIFFUSION MECHANISM OF SiC_f/TC17 COMPOSITE

采用磁控溅射先驱丝法并结合真空热压技术制备SiC_f/TC17复合材料,并在973,1023,1073和1123 K进行长时热暴露实验.结果表明,在热压和热暴露过程中,界面附近的元素扩散形式主要为化学反应和浓度梯度导致的界面互扩散,以及基体相变扩散.化学反应扩散是C和Ti扩散的主要动力,也是反应层形成和长大的原因;原于浓度梯度使Si,Al,Mo,Cr,Zr和Sn在C层/反应层界面进行下坡扩散,但扩散程度有限;基体相变扩散使Al向α相偏聚,Mo和Cr向β相偏聚,Sn向Ti_3AlC偏聚,同时使这些元素的界面互扩散受到抑制.界面热稳定性研究表明,SiC_f/TC17复合材料的反应层长大激活能为138 kJ/mol,该材料界面在973 K及以下温度是长时稳定的.

SiCf/TC17 composites were fabricated by a method of precursor wire with magnetron sputtering using a vacuum hot pressing （VHP） process and then exposed in vacuum at 973, 1023, 1073 and 1123 K for different times, respectively. The results show that element diffusions include interdiffusion caused by interracial reaction and concentration gradient, and phase transformation diffusion in matrix. C and Ti growing up of reaction layer. mainly carry on reaction diffusion Si, Al, Mo, Cr, Zr and Sn carry which is the reason of formation and on downhill diffusion at interface of C-coating layer and reaction layer, but this type of diffusion is not obvious. Phase transformation diffusion in matrix lead to that A1 diffuse to a phase, Mo and Cr diffuse to/3 phase, and Sn diffuse to Ti3AlC, so the interfacial interdiffusions of these elements is suppressed. The results of the interracial thermal stability show that the activation energy of reaction lay growing up is 138 kJ/mol, and the interface of SiCf/TC17 composite is stable for long time while it is used not above 973 K.