晶界Bi偏聚对＜110＞取向Cu三晶断裂行为的影响

INFLUENCE OF Bi SEGREGATION ON THE FRACTURE BEHAVIOR IN <110> TILT Cu TRICRYSTAL

研究了＜１１０＞取向倾侧Ｃｕ－Ｂｉ三晶晶界脆性与结构的关系，晶界Ｂｉ偏聚对Ｃｕ三晶形变和微观断裂过程的影响，并与＜１１０＞取向对称倾侧Ｃｕ－Ｂｉ双晶结果进行比较，结果表明：Ｂｉ的选择偏聚使Ｃｕ三晶中各晶界的脆性不同，这与双晶中的结果相似，但三晶的晶界在形变断裂中表现的特性，还与晶界和应力轴的取向关系及晶界间的相互作用有关．

he tension test and SEM observation of <110> tilt Cu-Bi tricrystal are done, in order to investigate the relation of embrittlement and structure for grain boundary as well as the influence of Bi's segregation in grain boundaries on the microprocess of deformation and fracture in tricrystal,and made a contrast with that of Cu -Bi bicrystal. The results indicate that the selective segregation of Bi atoms in different grain boundaries produce different degree embrittlement in each grain boundary. There is three kinds of fracture modes in tension test.Σ33a and 46°radom boundary fracture intergranularly while being main grainboundary and have the lowest fracture stress, showing the highest embrittlement; Σ11 tear intergranularly.showing less embrittlement;Σ3 fracture transgranularly. showing no embrittlement. this is similar to the results in Cu- Bi bicrystal. The difference in tricrystal and bicrystal is that the feature for grain boundary in tricrystal showing in fracture behavior relate to not only segregation of Bi atoms in grain boundary. but alsoorientation between the grain boundary and the stress axle as well as interaction between the grain oundaries, so that. the same grain boundary in the same tricrytal has different deformation and fracture mode whenstress axle orientation is changed. and the same grain boundary has different deformation and fracture modein tricrystal and bicrystal. Such as Σ33a fracture intergranularly while it being main grain boundary.but fracture transgranularly while Σ11 or Σ3 being main grain; Σ33b. which fracture transgranularly in bicrystal, tearintergranularly in tricrystal Σ33+Σ1+Σ3. A discussion based on atom simulation of these grain boundarieshas been taken.