2219-O铝合金声软化效应建模与预测

Modeling and prediction of acoustic softening effect of 2219-O aluminum alloy

超声振动辅助加工技术目前已广泛应用在金属的塑性成形过程中,已有研究表明超声振动的引入会令塑性成形过程出现声软化效应。对超声辅助拉伸条件下的形变材料进行电子背散射衍射(EBSD)观测时发现其晶粒尺寸有所增大。针对此现象推导了与超声振幅相关的应变-晶粒尺寸关系式,并基于Hall-Patch关系建立了晶粒尺寸变化对应力-应变曲线影响的模型,使用粒子群算法开展参数识别,利用所建模型对高超声振幅拉伸过程的声软化效应进行预测。通过2219-O铝合金的超声拉伸试验及EBSD微观结构组织观测验证了模型的正确性,进一步分析表明随应变增加,拉伸过程形变材料会出现硬化现象,而超声能量的引入会在一定程度上抵消拉伸过程中出现的硬化,且抵消的效果强度与超声振幅大小正相关。随超声振幅升高,晶粒尺寸增大的趋势更为显著,且在相同的应变条件下流动应力会随晶粒尺寸增大而降低。通过模型预测定量分析发现相同应变条件下,超声振幅每提高3μm,拉伸应力下降约6.5%。

The ultrasonic-assisted technology has been widely used in the metal manufacture process based on the softening effect of ultra-sonic energy.It was found by Electron Backscattered Diffraction(EBSD)observation that the grain size of the deformed materials under ultrasonic-assisted uniaxial tensile was increased.In view of this phenomenon,a strain-grain size relationship related to ultrasonic amplitude was established,and a model for the effect of grain size on the stress-strain curve was established based on the Hall-Patch relationship.The particle swarm optimization algorithm was used to identify parameters.Then,the model was used to forecast the acoustic softening effect of high ultrasonic amplitude uniaxial tensile process,and was verified by the ultrasonic uniaxial tensile test and EBSD observation of the 2219-O aluminum alloy.Further analysis shows that with the increase of strain,the tensile material would harden.The introduction of ultrasonic energy could offset the hardening in the uniaxial tensile process to a certain extent,and the offset effect was positively correlated with the ultrasonic amplitude.With the increase of ultrasonic amplitude,the grain size increased more significantly.Besides,under the same strain,the flow stress decreased with the increase of grain size.The quantitative analysis of model prediction shows that the tensile stress decreases about 6.5%when the ultra-sonic amplitude increased by 3μm under the same strain.