In Situ Observation of Laser‐Induced Melting and Solidification Behavior of ZrB 2 –SiC Composites
Shuntaro Ida, Kohei Morishita, Teiichi KimuraABSTRACT
Additive manufacturing of ultrahigh‐temperature ceramics, such as ZrB 2 –SiC composites, remains challenging owing to limited understanding of laser‐induced melting and solidification behavior across a wide composition range. We investigated the melting and solidification behavior of ZrB 2 –SiC powder compacts during laser irradiation using microstructural analysis and in situ synchrotron radiation x‐ray imaging. Laser irradiation formed melted and sintered regions. A partially melted region containing both melted and sintered microstructures was observed between these regions. The eutectic composition of the laser‐melted ZrB 2 –SiC composites was estimated to lie between ZrB 2 –57.5 mol% SiC and ZrB 2 –60 mol% SiC. Compositions far from eutectic, such as ZrB 2 –50 mol% SiC and ZrB 2 –70 mol% SiC, exhibited cracks and voids, whereas such defects were rarely observed in near‐eutectic composition melted regions. In situ transmission imaging revealed melting, solidification, and void formation during laser irradiation and subsequent cooling, consistent with post‐process microstructure observations. ZrB 2 in eutectic microstructure exhibited a blocky morphology with its primary growth direction <0001> approximately parallel to the solidification direction, whereas SiC formed a rod‐like morphology with the <110> primary growth direction approximately parallel to the solidification direction. Thus, near‐eutectic compositions in the ZrB 2 –SiC system enable effective densification and microstructural control through laser‐induced melting and solidification.