This paper deals with recent activities at the Laser Zentrum Hannover e.V. regarding a new visualization system based on frequency selective lighting and observation of dynamic melting pool behavior of an aluminum diecast alloy during short-time laser interaction.
Experimental measurements have been performed for the visualization of the temporal and spatial development of phase transitions during the melting and solidification process due to changes in reflection and backscatter properties of the material surface. The main aim of the work is the elaboration of an experimental set-up for the generation of image data for the quantitative determination of process parameters relevant for rapid solidification of aluminum alloys, e.g. melting and solidification front velocity. From this experimental data, estimations concerning grain textures dependent on material properties, and actual laser beam and processing parameters can be obtained. The aluminum alloy is remelted using an Nd:YAG solid-state slab laser system (λ=1064 nm), providing pulse durations in the μs-range and high pulse peak power. Frequency selective lighting of the processing zone is realized by using a frequency doubled Q-switched Nd:YAG laser system at a wavelength of 532 nm and pulse durations of 10 ns. Image data related to the temporal development of the solid and liquid isotherms are compared to the results of numerical calculations using the finite difference method (FDM) [1].