不同结构金属中疲劳裂纹扩展机理的原子模拟

Atomic Simulation of Fatigue Crack Propagation in Metals of Different Structures

采用分子动力学的方法模拟了铁(BCC)和镍(FCC)在常温下的疲劳裂纹扩展行为,对比分析了裂纹在不同结构的金属中尖端微观结构的演变。研究结果表明单晶铁中[001](010)裂纹扩展时表现出韧性开裂,裂纹尖端主要的变形机制为剪切滑移带和钝化效应,滑移系为[111](110);铁中[110](110)裂纹表现出脆性断裂,滑移系为[110](110);对于[112](111)裂纹,位错是疲劳裂纹尖端主要的变形机制。而在单晶镍中,[001](010)裂纹在常温下以钝化效应开始萌发,而在裂纹扩展中,驻留滑移带是裂纹前端主要的变形机制,滑移系为[110](111);镍中[110](110)裂纹尖端的主要变形为位错线,并且在(111)面形成了滑移带;而[112](111)裂纹尖端的滑移带却沿着[123]和[132]方向滑移,滑移面为{111}面。

Molecular dynamics is adopted to simulate the fatigue crack propagation of the iron (BCC) and nickel (FCC) at room temperature. The microstructure evolution at crack tip is analyzed in metals of different structures. The results showed that the [001](010) crack presents toughness crack in single iron, and the main deformation mechanisms of crack tip are shearing slip bands and the slip system is{110}, and the [110](110) crack of iron shows brittle fracture and the slip system is{110}. For the [112](111) crack of iron, the dislocations are the main deformation mechanism at crack tip. But in the single nickel, the [001](010) crack germinates as the effect of blunting, and propagates with slip bands in the crack propagation and the slip system is [110](111). In the [110](110) crack of nickel, the main deformation mechanism is the dislocation line, and forming slip band along (111) plane. For the [112](111) crack in single nickel, the slip bands are along the [123] and [132] direction in {111} plane.