Microstructural characterization of Al2O3-ZrO2 ceramic by laser direct material deposition

Laser direct material deposition (LDMD) as a new fabrication method can rapidly fabricate complex parts without molding. In order to research the microstructure characteristic of the deposit structure, the thin-wall structure of different powder weight ratios was fabricated by using LDMD. The porosity of different regions of different powder ratios was discussed. The microstructure characteristic and the phase composition were analyzed by scanning electron microscopy and x-ray diffraction, respectively. The result showed that macrodefects mainly appeared in the central region of the deposit structure. Macrocracks appeared in the central region of H1 hypoeutectic and H2 hypereutectic deposit structures. Macropores and contraction cavities appeared in the upper and central regions of the deposit structure. With increasing the content of ZrO2, the pore morphology in the central region transformed into an irregular pore connection from a regular pore. However, the size and the number of pores in the frontier region decreased with the increase in the ZrO2 content. The microstructure characteristic of different regions of different powder ratios was similar to the pore morphology characteristic. The ratio of the eutectic microstructure and the grain size in the central region were larger than those in the frontier region. The grain size decreased with an increase in the ZrO2 content. The results of this research provide the basis for attaining good quality Al2O3-ZrO2 ceramics by laser direct material deposition.