Takahashi Shun, Yoshida Sanichiro, Sasaki Tomohiro, Hughes Tyler
Graduate School of Science and Technology, Niigata University, Niigata 9502181, Japan.
Department of Chemistry and Physics, Southeastern Louisiana University, Hammond, LA 70402, USA.
Materials (Basel). 2021 Mar 20;14(6):1530. doi: 10.3390/ma14061530.
The deformation and fracture mechanism in 7075 aluminum alloy is discussed based on a field theoretical approach. A pair of peak-aged and overaged plate specimens are prepared under the respective precipitation conditions, and their plastic deformation behaviors are visualized with two-dimensional electronic speckle pattern interferometry (ESPI). The in-plane velocity field caused by monotonic tensile loading is monitored continuously via the contour analysis method of ESPI. In the plastic regime, the peak-aged specimen exhibits a macroscopically uniform deformation behavior, while the annealed specimen exhibits non-uniform deformation characterized by a localized shear band. The occurrence of the shear band is explained by the transition of the material's elastic resistive mechanism from the longitudinal force dominant to shear force dominant mode. The shear force is interpreted as the frictional force that drives mobile dislocations along the shear band. The dynamic behavior of the shear band is explained as representing the motion of a solitary wave. The observed decrease in the solitary wave's velocity is accounted for by the change in the acoustic impedance with the advancement of plastic deformation.
基于场论方法讨论了7075铝合金的变形与断裂机制。在各自的析出条件下制备了一对峰值时效和过时效板材试样，并用二维电子散斑干涉术（ESPI）对其塑性变形行为进行了可视化。通过ESPI的轮廓分析方法连续监测单调拉伸加载引起的面内速度场。在塑性状态下，峰值时效试样表现出宏观均匀的变形行为，而退火试样表现出以局部剪切带为特征的非均匀变形。剪切带的出现是由材料的弹性阻力机制从纵向力主导模式向剪切力主导模式的转变来解释的。剪切力被解释为驱动可移动位错沿剪切带运动的摩擦力。剪切带的动态行为被解释为代表孤立波的运动。孤立波速度的观测下降是由随着塑性变形的进展声阻抗的变化来解释的。
