TiAl合金细小全层片组织断裂机理

对多重热处理得来的铸造Ｔｉ－４６．５Ａｌ－２．５Ｖ－１．０Ｃｒ－０．２Ｎｉ（原子分数，％）合金细小全层片（ＦＦＬ）组织断裂韧性试样侧面和断口形貌及裂纹区位错、孪晶结构进行了观察分析．发现ＦＦＬ组织具有和ＦＬ组织相同的断裂特征，即多重断裂和裂尖区充分形变．但层片团尺寸的大幅度减小使得单个剪切带对应变能的消耗减小较多，且使裂纹扩展中总的变形体积减小，从而减弱了剪切带的韧化作用，使ＦＦＬ组织具有相对ＦＬ组织较低的断裂韧性．

FRACTURE MECHANISMS OF FFL MICROSTRUCTURE IN TiAl ALLOY

The observations of the crack morpholgies on the side faces and fracture surfaces of the fracture toughness specimens and the TEM analyses of deformed structure around crack were conducted for the FFL microstructure which was obtained from the cast Ti-46.5 Al-2.5V-1.0Cr-0.2Ni(atomic fraction,%) alloy by a designed multiple heat treatment.The fracture characterizations of the FFL microstructure are similar to that of the FL microstructures.The functions of each shear ligment and total deformed volume accompanying the crack in the FFL microstructure were much smaller due to the significant decrease of the lamellar colony size.This led to a descent of fracture toughness of the FFL microstructure compared to the general FL microstructure.