Ti-6Al-2C合金中片状TiC的形成机制

Forming Mechanisms of Plate-shape TiC in Ti-6Al-2C

通过适当的高温热处理工艺 ,可改变TiCp Ti复合材料中枝晶状TiC的形态和尺寸 ,不同的热处理工艺 ,使枝晶TiC变成不同的形态。Ti 6Al 2C(w ,% )合金在 1 2 0 0℃保温 1 0 8ks可使枝晶状TiC粒化 ,但 1 1 0 0℃保温 2 1 6ks时得到平行分布的片状TiC。从理论上初步探讨了片状TiC的形成机制 ,认为TiC可在α Ti(0 0 0 1 )基面上 ,由Shockley位错运动形成的层错区直接生核。从动力学分析TiC沿 [0 0 0 1 ] α Ti方向生长时碳原子需长程扩散 ,而沿α Ti的 [1 1 2 0 ]方向生长时扩散距离很短 ,因此极短的生长时间内 ,TiC只能沿 [1 1 2 0 ] α

The size and morphology of dendritic TiC in TiC\-p/Ti alloy can be changed by adopting appropriate heat treatment processing. Under different heat treatment conditions, dendritic TiC formed in different morphologies. Dendritic TiC in Ti\|6Al\|2C( w ,%) alloy was sphericized by heat treatment at 1200℃ for 108ks. However, dendritic TiC treated in the condition of heat treatment at 1100℃ for 216ks transformed into parallel distribution plate\|shape. The forming mechanisms of plate\|shape TiC were discussed in terms of the crystal structure and atom packing theories. At the (0001) plane of α\|Ti having supersaturation C the fault formed due to Shockley dislocation motion was considered as grain cell of TiC. The growth impediment of TiC grain cell along \ direction of α\|Ti is higher than {1120} direction of α\|Ti, so TiC quickly transformed into plate\|shape along {1120} direction of α\|Ti.