热处理对Ti-6Al-2C合金中TiC枝晶形貌的影响

Effect of Heat Treatment on Morphology of TiC in Ti-6Al-2C Alloy

用熔铸法制备 Ti- 6 Al- 2 C合金 ,采用 XRD,SEM和 EPM研究了合金的铸态组织及热处理对 Ti C枝晶形貌的影响。合金的铸态组织中枝晶状 Ti C,在 12 0 0℃保温并淬火时 ,随保温时间的延长 ,Ti C枝晶逐步溶断为秃枝 ,最终成为 8～ 2 0μm大小的粒状。从微区碳浓度平衡关系研究 Ti C枝晶的溶断过程 ,建立了首先从枝晶根部溶解的粒化模型 ,Ti C的二次或三次枝晶根部表面的曲率大 ,对应基体中平衡碳浓度高 ,高温下碳的扩散破坏这种局部碳浓度的平衡 ,使大曲率处的 Ti C溶解 ,最终导致根部的溶断 ,成为粒状 Ti C。溶断过程的

Ti 6Al 2C alloy was produced using casting process The as cast microstructure of alloy and the effect of heat treatment on TiC morphology had been investigated by XRD, SEM, and EPM TiC in as cast alloy had dendritic shape and gradually transformed into bare branches after heat treated at 1200℃ and water quenched With increasing holding time, TiC dendrite finally transformed into particles with size of 8～20μm The dissolving process of dendrite TiC was studied according to C concentration balance in micro zone and in terms of the studies the granulation model was built This model indicated that the dissolving and breaking up of dendrite TiC always occur at the root sites of secondary and third dendrite arm where had larger surface curvature corresponding to higher C concentration in Ti matrix The diffusion of C at high temperature disturbed the C concentration balance, which led to the dendrite TiC to dissolve and break up into particles