基于二维连续位错动力学模型的超声软化机制研究

Research on ultrasonic softening mechanism based on 2D continuum dislocation dynamics model

基于位错动力学理论,通过研究位错间的相互作用,建立了二维连续位错动力学模型。基于此模型,以纯铝400℃恒应变速率下的变形为研究对象,对位错密度、位错组态和流动应力随时间的演化进行了模拟,分析了变形过程中各种位错花样的形成原理。结果表明,较大的应变速率会增大材料流动应力和位错密度,强化位错墙结构,细化位错胞结构,通过与文献中的实验数据进行对比,验证了模型的可靠性。在此模型的基础上,考虑了施加超声振动外场的影响,通过模拟位错组态演化,对超声软化作用和晶粒细化现象进行了定量预测,结果表明,施加超声振动后,材料流动应力、位错密度和晶胞尺寸均降低。

Based on the theory of dislocation dynamics,a 2 D continuum dislocation dynamics model was established by investigating the interaction between dislocations.Based on this model,taking the deformation of pure aluminum at 400℃and constant strain rate as the research object,the evolution of dislocation density,dislocation configuration and flow stress with time was simulated and the formation mechanism of various dislocation patterns during the deformation process was analyzed.The results show that larger strain rate can increase the flow stress of material and dislocation density,strengthen the structure of dislocation wall and refine the structure of dislocation cell.By comparison with experimental data in the literature,the reliability of the model was verified.On the basis of this model,considering the influence of applying external ultrasonic vibration field,the ultrasonic softening effect and grain refinement phenomenon were quantitively predicted by simulating the dislocation configuration evolution.The results show that after applying ultrasonic vibration,the flow stress of material,dislocation density and cell size decrease.