(1. 重庆理工大学 机械工程学院，重庆 400054；
2. 合肥工业大学 材料科学与工程学院，合肥 230009)
摘 要: 采用分子动力学方法研究了单轴拉伸载荷下扭转晶界(Twist boundary, TB)扭转角和晶向对含微缺陷的纳米镍双晶断裂的影响机理。结果表明：扭转角和晶向决定了扭转晶界处失配位错密度大小，影响位错的形核与发射。随着扭转角的增加，晶界处位错形核与发射增多，裂纹扩展加快，孔洞变形变小，镍双晶断裂从0°时由孔洞导致变为45°时由裂纹扩展导致。对含有不同晶向扭转晶界的镍双晶，(110)扭转晶界镍双晶相比于(010)和(111)扭转晶界镍双晶具有更大的裂纹扩展速率，塑形变形的集中也让孔洞长大不明显，并在应变达到0.3之前就已经完全断裂。而(110)与(111)扭转晶界镍双晶裂纹扩展较难，孔洞长大明显，并在应变达到0.3时也未发生完全断裂，因此拥有更好的延展性。
关键字: 镍双晶；分子动力学；扭转晶界；扭转角；晶向；孔洞；裂纹
（1. College of Mechanical Engineering, Chongqing University of Technology, Chongqing 400054, China;
2. College of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China）
Abstract:The molecular dynamic simulation was conducted to analyze the influences of twist angle of twist boundary (TB) and orientation on fracture of nano-nickel bicrystal with micro-defects under uniaxial tensile loading. The result shows that the twist angle and orientation determine the density of misfit dislocations at the twist boundary, affecting the nucleation and emission of dislocations in nickel bicrystal. With the increase of twist angle, the nucleation and emission of dislocation at grain boundaries gradually increase, the cracks propagate forward more quickly, and the deformation of the void becomes smaller, so that the fracture caused by void growth at 0° changes to the fracture caused by propagation of the cracks at 45°. For nano-nickel bicrystal with twist boundaries in different crystal directions, (110) twist boundary nickel bicrystal has a greater crack growth rate compared to (010) and (111) twist boundary nickel bicrystals, the concentration of plastic deformation also makes the void growth not obvious, and it is completely fractures before the strain reaches 0.3. However, the crack propagation of the (110) and (111) twist boundary nickel bicrystals is more difficult, and the void growth is more obvious. And the (110) and (111) twist boundary nickel bicrystals not completely fracture when the strain reaches 0.3, so they have better ductility and malleability.
Key words: nickel bicrystal; molecular dynamics; twist boundary; twist angle; orientation; voids; crack
