Ultrasonic energy attenuation characteristics in plastic deformation of 2219-O aluminum alloy

Abstract

In the ultrasonic-assisted metal forming process, the dislocations within the material are easier to move due to the absorption of ultrasonic energy, which can effectively promote material flow and improve the formability of components, this phenomenon is called the ultrasonic softening effect. The ultrasonic softening effect is generally treated as homogeneous at the whole materials for simplicity, while the attenuation of the ultrasonic energy along the propagation direction will bring inhomogeneous distribution of softening degree. In addition, the absorption of the ultrasonic energy by material is also affected by the dislocation movements in the metal plastic processing procedure, resulting in the variation of the ultrasonic attenuation characteristics in the material with the plastic deformation, the current research has little concerned it. In this paper, the ultrasonic attenuation properties in 2219-O aluminum alloy with plastic strain were investigated. The influence of the dislocations and the dislocation movements caused by plastic deformation on the ultrasonic attenuation was characterized. The pre-strain specimen was designed to indicate the degree of plastic deformation of the material, and the specimen thickness direction was defined as the propagation direction of the ultrasonic energy. The experimental results and the microstructure observation showed that the absorption of ultrasonic energy by the material increases firstly and then decreases with the plastic strain increasing, which is related to the evolution of movable dislocations within the material. In order to accurately describe the ultrasonic energy attenuation characteristics in plastic deformation, the hardening equation of 2219-O aluminum alloy considering ultrasonic propagation distance and plastic strain was built and the model accuracy was verified based on the experimental data.