Ultrasonic compression hardening

Influence of ultrasonic on the compression hardening behavior of metallic materials

Ultrasonic vibration can lead to an improvement in manufacturing process and therefore optimizing the process. Blaha and Langenecker researched the basis of the effect in the 1960s, firstly. They found that the flow stress in a tensile test dropped, when ultrasonic vibration is superimposed during the tensile test. Some materials display a temporary or a residual hardening after the ultrasonic treatment. The cause of the so called acoustic softening and hardening is not fully understood. The literature describes different tests and explanatory ideas for the acoustic softening, while the residual hardening has received little attention in the literature so far. The most commonly investigated materials are face centered cubic (aluminum alloys) or hexagonal (zinc) materials, while a lot of technical application is focused on steels. The project aims to systematically investigate under which condition acoustic softening and hardening occurs for a ferritic, body centered cubic and an austenitic face centered cubic steel. Therefore, it is necessary todevelope a new quasi-static compression test setup, which allows the introduction of ultrasonic pulse at a specific point during the test with variable ultrasound amplitudes and durations to the specimens. The tests will be performed on both materials, analyzing how an initial dislocation density and the ultrasonic parameters like amplitude or power interact with the acoustic softening und hardening. The mechanical material reaction are measured during and after the superimposed ultrasonic treatment. The microstructure changes are characterized with SEM, EBSD images and local instrumented hardness/indentation tests. The aim is to deduce a metal physical explanation for the ultrasonic softening and hardening from these results. It is the main aim to find out the metal physical mechanism for the acoustic softening and hardening.

Contact person: M. Sc. Markus Burmeister