SURFACE TENSION DRIVEN KINETICS OF THE TRIPLE LINE OF A LIQUID METAL FREE SURFACE

Spreading kinetics of molten Al-Si alloy on both alumina and aluminum surfaces, driven by surface tension and retarded by viscosity, with or without significant impact of gravity, has been studied experimentally. Spreading takes place during a transient formation of the free liquid metal surface in a wedge-tee configuration corner between horizontal and vertical metal mating surfaces with a small Bo number. A high temperature optical dynamic contact angle measuring system has been used to monitor in real time in situ the free surface formation. Tests were performed under different oxygen concentration levels and at atmospheric pressure conditions, with a benchmark case involving ultra-high purity Nitrogen. An auxiliary study of the surface tension of the particular molten alloy considered has been performed under conditions of a large Bo number as well. These tests were performed over a flat non-wetting ceramic substrate of pure alumina (96%) using an optical sessile drop method. The former experiments resulted in capturing a 2-D configuration of the observed alloy liquid formation at elevated temperatures during a time evolution of the molten metal free surface spreading. The kinetics of the triple line movement at the vertical mating surface constitutes the main objective of the study. It is established that the triple line kinetics features a sequence of multiple, well defined spreading phases. These phases of the joint formation were identified, and the influential parameters were assessed. The power law spreading kinetics has been established. The experimental results show a good agreement with the hypothesized theoretical model.