Molecular Dynamics Simulation of Interaction between Edge Dislocation and MnNi-rich Precipitate in α-Fe

The interactions of the 1/2〈111〉110 edge dislocations with a MnNi-rich precipitate were investigated by molecular dynamics method. It is found that the increase of precipitates size enhances their obstacle strength, while, the rise of temperature causes the reducing of obstacle strength. The results indicate that the critical resolved shear stress of the MnNi-rich precipitate is larger than that of Cu precipitate. For 2 nm and 3 nm MnNi-rich precipitates, the effect of Mn atoms on dislocation slip is greater than that of Ni atoms, and Mn atoms tend to assemble in the dislocation segment and play the role of dragging dislocation motion. In addition, it will happen to the phase transformation from body centered cubic structure to face centered cubic and close-packed hexagonal structure in 4 nm MnNi-rich precipitate, improving the resistance of dislocation movement. With the increase of temperature, the drag effect of Mn atoms on the dislocation fragment is weakened, and the phase transformation degree of the precipitates decreases. These result in a significant decrease of the critical shear stress of the MnNi-rich precipitates, showing significant temperature dependence. In summary, MnNi-rich precipitates are stronger obstacles for the motion of dislocations than pure Cu precipitates, greatly facilitating the irradiation hardening in α-Fe matrix.