Transformation dynamics, pattern selection, and mechanical properties of B₄C-TiB₂ eutectic ceramics fabricated by optical floating zone melting

Directionally solidified B₄C-TiB₂ eutectic ceramics are fabricated via optical floating zone (OFZ) method. Their microstructures and mechanical properties were analyzed by means of high-throughput characterization and image recognition analysis technology. The results show five different typical morphologies of eutectics. Quantitatively analysis based on high-throughput characterization results revealed that the width, length, length/width (L/W) ratio, area fraction of the TiB₂ second phase were inhomogenously distributed along the specimen. Three-dimensional reconstruction visualized the spatial structure of eutectics, indicating a lamellar-rod transition that many be attributed to the amplified varicose instability of lamellar eutectic; rod-like eutectic is also observed adjacent to the coarse B₄C phase within colony structure. Vickers hardness tested by indentation array exhibited a bimodal distribution with an average value of approximately 47.8 GPa. Indentation size was comparable to the eutectic phase, with higher hardness observed in B₄C lamellae especially near the TiB₂ lamellar tip and lower hardness in TiB₂ lamellae.