α-Fe中刃型位错和富MnNi析出物相互作用的分子动力学模拟研究

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

本文采用分子动力学方法对α-Fe中1/2〈111〉{110}刃型位错和富MnNi析出物的相互作用进行了系统性研究。发现体系的临界剪切应力随析出物尺寸的增加而增大,随温度的升高而降低。富MnNi析出物和位错相互作用的临界剪切应力大于纯Cu析出物的。对于2 nm和3 nm富MnNi析出物,Mn原子对位错滑移的影响作用大于Ni原子的,Mn原子倾向于聚集到位错段,起拖拽位错运动作用。4 nm富MnNi析出物出现了体心立方相转变为面心立方和密排六方相现象,进一步提高了析出物对位错滑移的阻碍作用。随着温度的升高,Mn原子对位错段的拖拽作用减弱、析出物的相变程度降低,导致富MnNi析出物对应的临界剪切应力降低,呈较显著的温度依赖性。总而言之,相比于纯Cu析出物,富MnNi析出物表现出对位错滑移更强的钉扎作用,增强了基体的辐照硬化程度。

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 inα-Fe matrix.