An energy based modeling for the acoustic softening effect on the Hall-Petch behavior of pure titanium in ultrasonic vibration assisted micro-tension
An energy based modeling for the acoustic softening effect on the Hall-Petch behavior of pure titanium in ultrasonic vibration assisted micro-tension
复制标题
基于能量的超声振动辅助微张力下纯钛 Hall-Petch 行为的声软化效应建模
DOI：
10.1016/j.ijplas.2020.102879
复制
发表时间：
2021-01-01
影响因子：
9.8
通讯作者：
Shan, Debin
中科院分区：
文献类型：
--
作者：
Wang, Xinwei;Wang, Chunju;Shan, Debin
在过去的几十年里，人们对金属塑性变形过程中的声软化效应进行了广泛的研究。然而，这种声学可塑性的机制仍然存在争议。因此，从应力叠加理论、热激活理论、晶体塑性理论和其他与位错演化相关的机制出发，提出了几种模型来解释声软化效应。在本研究中，我们提出了一种在超声振动辅助(UVA)变形过程中非热位错动力学在微观水平上发生非均匀变化的机制。具体地说，将位错弹出晶界所需的功可能会被晶内位错和晶界位错的声能吸收差异所改变。通过在位错弹出功中引入声能密度的幂函数，模拟了声软化效应对Hall-Petch行为的影响。为了验证所建立的模型，对纯钛试件进行了UVA微拉伸试验。结果表明，超声振动引起的Hall-Petch斜率减小，随着塑性变形的增加，超声引起的Hall-Petch斜率减小的幅度增大。注意，我们的模型预测与低应变下的实验结果吻合得很好，提供了一种对Hall-Petch行为的声学软化效应的另一种洞察。微观组织分析表明，在微张力作用下叠加超声振动可以延缓钛箔织构的演化，导致位错密度降低，位错密度降低，位错密度增加，位错密度降低。这在一定程度上支持了我们的模型假设，即声能依赖性降低位错密度，增强位错喷射，从而改善塑性相容性。
The acoustic softening effect in metals during plastic deformation has been widely investigated in the past decades. However, the mechanism of such an acoustic plasticity remains controversial. As a result, several models were proposed to understand the acoustic softening effect in terms of stress superposition, thermal activation theory, crystal plastic theory and other mechanisms associated with dislocation evolution. In this study, we proposed a mechanism that the athermal dislocation dynamics may heterogeneously change at microstructure level during ultrasonic vibration assisted (UVA) deformation. Specifically, the work required to eject dislocations from grain boundaries may be altered by the acoustic energy absorption difference of a dislocation in the grain interior and one in the grain boundary. As a result, the acoustic softening effect on the Hall-Petch behavior was modeled by incorporating a power function of acoustic energy density into the dislocation ejection work. To validate the developed model, UVA micro-tension tests were conducted on pure titanium specimens. Results showed that the Hall-Petch slope decreased due to ultrasonic vibration, and the ultrasound-induced decrease of the Hall-Petch slope increased with plastic deformation. Note that our model predictions matched well with the experimental results at the lower strains, providing an alternative insight into the acoustic softening effect on the Hall-Petch behavior. Microstructure examinations showed that the superimposed ultrasonic vibration in micro-tension could lead to the retardation of texture evolution, the decreases in kernel average misorientation (KAM) value, low-angle grain boundary (LAGB) fraction and dislocation density in titanium foils, which somewhat supported our model assumptions in terms of the acoustic energy dependent reduction in dislocation density and the enhanced dislocation ejection causing the improvement of plastic compatibility.