The surface tension of a metal is an important property for many applications, but is rather unknown for high temperatures. Physical theories predict that surface tension is very low at vaporization temperature. However, in practice, surface tension is observable. Therefore, the purpose of the project is to explain the physical effects that influence the surface tension of evaporating surfaces.
Based on the material evaporation rate and the surface temperature, the acting forces determine the surface tension. It will be investigated how the surface reacts on the loss of evaporated particles and how this affects the surface tension. In addition, a measuring method based on laser irradiation of falling metal drops including temperature and high-speed imaging is proposed to determine metal material surface tension at surface temperatures above vaporization temperature.
The project results promise new insight in the behavior and properties of metal materials at superheated surfaces. The results are valuable for many high temperature material testing and processes using lasers, e.g. during welding, drilling, cutting or surface structuring.