Molecular dynamics simulation of Ashby-Verrall superplasticity model for nano-crystal

The deformation of Ashby-Verrall multi-crystal superplastic model is studied through molecular dynamics (MD) simulation using Al nano-crystal as an instance. Under 0 K-400 K, the grain boundaries with large tilt angle are easy to slide and the results agree well with Ashby-Verrall model; however, grain boundaries with small tilt angle are difficult to slide. When the simulating temperature is up to 600K, the interfaces melt and tiny liquid phases exist on them. Grain boundaries with small tilt angle can also start moving with the flowing of the liquid phase. At the same time, the grains rotate to the orientation is advantage to the deformation, and the Ashby-Verrall movement is accomplished. The deformation mechanism of single crystal in the model fits the Gifkins' 'center-surface' model.