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

Laser direct material deposition (LDMD) as a new fabricate method, can rapidly fabricate the complex part without mold. To research the microstructure characterizatic of deposit structure, the thin-wall structure of different powder weight ratios were fabricated by using LDMD. The porosity of different regions of different powder ratios was discussed. The microstructure characteristic and phase composition were analyzed by the scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. The result showed that the macro-defects mainly appeared in the central region of deposit structure. Macro-cracks appeared in the central region of H₁ hypoeutectic and H₂ hypereutectic deposit structure. The macro-pores and contraction cavities appeared in the upper and central region of deposit structure. With the content of ZrO₂ increased, the pore morphology in the central region transformed into the irregular pore connection from the regular pore. However, the size and number of pore in the frontier region decreased with the content of ZrO₂ increased. The microstructure characteristic of different regions of different powder ratios was similar to the pore morphology characteristic. The ratio of eutectic microstructure and the grain size in the central region were larger than that of the frontier region. The grain size decreased with the content of ZrO₂ increased. The results of this research provide the basis for attaining good quality Al₂O₃-ZrO₂ ceramics by laser direct material deposition.