(1. 重慶理工大學 機械工程學院，重慶 400054；
2. 合肥工業(yè)大學 材料科學與工程學院，合肥 230009)
摘 要: 采用分子動力學方法研究了單軸拉伸載荷下扭轉晶界(Twist boundary, TB)扭轉角和晶向對含微缺陷的納米鎳雙晶斷裂的影響機理。結果表明：扭轉角和晶向決定了扭轉晶界處失配位錯密度大小，影響位錯的形核與發(fā)射。隨著扭轉角的增加，晶界處位錯形核與發(fā)射增多，裂紋擴展加快，孔洞變形變小，鎳雙晶斷裂從0°時由孔洞導致變?yōu)?5°時由裂紋擴展導致。對含有不同晶向扭轉晶界的鎳雙晶，(110)扭轉晶界鎳雙晶相比于(010)和(111)扭轉晶界鎳雙晶具有更大的裂紋擴展速率，塑形變形的集中也讓孔洞長大不明顯，并在應變達到0.3之前就已經完全斷裂。而(110)與(111)扭轉晶界鎳雙晶裂紋擴展較難，孔洞長大明顯，并在應變達到0.3時也未發(fā)生完全斷裂，因此擁有更好的延展性。
關鍵字: 鎳雙晶；分子動力學；扭轉晶界；扭轉角；晶向；孔洞；裂紋
（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
