Small scale deformation behavior of powder HPT-deformed Au – influence of production routes and temperatureThursday (29.09.2016) 15:30 - 15:45 Part of:
Small scale testing techniques are widely used for assessing local mechanical properties in order to shed more light into small scale deformation processes under ambient but also non-ambient conditions. Especially at elevated temperatures, a careful experimental setup is required in order to get reliable and reproducible data, since thermal drift issues play an important role and can dominate the apparent material characteristics.
In this work, the thermally activated deformation behaviour of Au was studied by applying different nanoindentation testing techniques from room temperature up to 400 °C. While for single crystalline Au the determined indentation properties, especially in terms of hardness and modulus, agree well with literature, the highly deformed ultrafine grained (ufg) Au sample shows a surprisingly low modulus at temperatures exceeding 200 °C. In order to better understand this phenomenon different other fcc materials such as Cu and Ag produced by both, bulk as well as powder HPT-fabrication, were additionally tested up to 400 °C. It is shown that for all materials the modulus of the powder deformed samples exhibits a pronounced reduction at higher temperatures, while for the bulk derived ufg-states the modulus behaves according to literature. The presented phenomenon is still not fully understood, however, it might be explained by a higher concentration of vacancies at the grain boundaries, with additional creep effects, or even with some changes in the sink-in formation due to different work hardening behaviours.