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Weight loss of alumina and zirconia targets during PLD

: Aden, M.; Kreutz, E.W.; Voss, A.


Journal of Physics. D. Applied Physics 28 (1995), S.2595-2599
ISSN: 0022-3727
Fraunhofer ILT ()
high power laser; laser radiation; phase transition; vaporisation; weight loss; zirconia

The weight loss due to laser-induced vaporization of aluminia and zirconia is investigated both theoretically and experimentally. To calculate the weight loss of the target under laser irradiation a model is used describing the laser-induced vaporization and the dynamics of the vapour/plasma state including the absorption of laser radiation. The weight loss is not an increasing function of the fluence over the whole range but has a local maximum due to absorption of laser radiation in the plasma state. The energy deposited in the plasma state due to the absorption of laser radiation is calculated and compared to the weight loss data. Different pulse shapes of laser radiation influence the maximum value of the weight loss but leave the principal dependence on the fluence unaltered. Furthermore, it is shown that increasing the back pressure from 0.06 to 100 mbar leads to considerably smaller weight losses. The software tool for process planning of laser beam welding CALAS is presented. I ts structure, handling and simulation capabilities are described in detail. Furthermore a connection to a commercial laser database and the integration into the overall laser processing strategy is shown for laser beam welding. The software tool connects a physical process model with an interactive man-machine interface by simulation and visualization. It shows on-line the effect of the process parameters on the geometry of the weld seam. It also provides a 3-dimensional visualization of the keyhole and the melt pool. Besides typical parameters also the beam characteristics and material properties like surface tension and heat transfer capability are included in the calculation. By using CALAS process planning will become much more efficient and the materials processing results show better quality because of the prediction of the seam geometry.