Molecular Dynamics Simulation Of The Effect Of Twin And Stacking Fault On The Mechanical Behavior Of Nanocrystal Metal

As a new type of material, nanomaterials have attract the attentions all over the world due to its superior force, electrical, magnetic, optical and chemical macroscopic properties in the aerospace, electronics, metallurgy, chemical, biological and medical fields. Compared with the ordinary coarse crystalline metal, nanocrystalline metal has many different properties and excellent performance. Normally, a material with good toughness, or high strength, but difficult to both, is generally the higher the strength of the material, the worse of the toughness; while the toughness is good, the strength is generally low. For a material, the cost of improving the strength is reducing its toughness. Recently, some research results show that when the nano-scale grain is refined, the high strength and toughness can be combined due to the different mechanism of plastic deformation. High strength and high toughness can be reached by keeping some microcrystalline. So in the deformation process, material in nano-scale may have high strength, and microcrystalline can stabilize the plastic deformation of the metal. Therefore, the understanding of the relationship between the nanocrystalline metal microstructure and its mechanical properties, as well as the reveal of the deformation mechanism from microcosmic, may have fundamental significance for the design of material for certain application requirements.Firstly, we investigate the mechanical properties for face centered cubic (FCC) aluminum, including:the single-crystal, twin with different twin spacing (TB), stacking fault with different spacing and its effect on material, the influence of temperature. We simulated the tips above in order to reveal:the mechanism of the interaction between the dislocations and the grain boundaries, dislocation and the stacking fault, dislocations and TB and so on.Secondly, we investigate the influence of crack on the nanotwinned aluminum, including:single-crystal with crack and nanotwinned, the crack with different initial crack orientation (the crack orientation is parallel with the coherent twin boundary (CTB) and the crack orientation is perpendicular to the CTB). We simulated the tips above in order to demonstrate the deformation mechanism, the interaction between the dislocations and the grain boundaries, the dislocation and the twin boundary, the twin boundary and the crack and so on.