钛硅共晶系合金结晶过程与微观形貌

Study on Crystallization Process and Microstructure of Ti-Si Eutectic Alloy Systems

观察和分析了钛硅共晶系合金的共晶结晶过程以及微观组织中Ti5Si3相的典型形貌。结果表明,亚共晶与共晶钛硅合金中Ti5Si3相在共晶析出时均生长成棒状甚至颗粒状。更细致的观察发现,Ti5Si3相的截面形貌为六角形,具有光滑的120°夹角界面,而且中心部位嵌有非共格的球形α-Ti颗粒。同时,Miedema理论计算结果表明,Ti5Si3相比β-Ti相具有更负的生成热,是钛硅共晶系合金中两相共晶时的领先相。

The eutectic crystallization processes of Ti-Si eutectic alloy systems and the types of Ti5Si3 phases involved in the microstructure have been investigated. The results show that the Ti5Si3 phases precipitated in the hypoeutectic and eutectic Ti-Si alloys form with rod-like or grain-like ones. More careful observation prove that the section shape of Ti5Si3 phase formed in the eutectic reaction is of smooth hexagon with an angle of 120° between the interfaces, and sphere-like α -Ti phase is found in the center of some Ti5Si3 bodies. The calculated results based on Miedema model revealed that the formation enthalpy of Ti5Si3 phase is more negative than that of β -Ti phase. Thus, the Ti5Si3 phase is the one to form firstly during the eutectic precipitation of Ti-Si eutectic alloy systems.