ZrO2–Al2O3 eutectic plates produced by laser zone melting

This paper describes a procedure for preparing large surfaces of eutectic composites directionally solidified from the melt, with very fine and uniform microstructures. Large surface plates of the Al2O3–ZrO2 eutectic, with thickness up to 250 μm, have been grown by solidification using a modified laser zone melting method suitable for the preparation of large area samples. The surface of a ceramic precursor is scanned with a rectangular CO2 laser beam of 20×0.5 mm2 size which induces surface melting. The resulting microstructure is colony free and it consists of fine and alternating interpenetrating Al2O3 and ZrO2 single crystal lamellae. This microstructure is the basis for improvement of mechanical behaviour in the processed material. The interspacing, crystal structure and orientation relationship between the phases has been determined. Solidification fronts were studied as a function of the processing conditions. A mapping of the residual stresses has also been performed along the transverse plate sections using micro-luminescence techniques.