Microstructure and mechanical properties of Al₂ O₃/Y₃Al₅O₁₂/ZrO₂ ternary eutectic materials

Directionally solidified fibers and rods have been grown from the ternary Al₂O₃/Y₃Al₅O₁₂ /ZrO₂ system using micro-pulling-down method. Fiber diameter could be varied 0.3 mm-2 mm at pull-rates ranging 6-900 mm/h and 500 mm in length. The ternary eutectic fibers had homogeneous colony patterned eutectic microstructures. The interlamellar spacing λ exhibited an inverse-square-root dependence on the growth speed v according to λ = 8 × v^-1/2, where λ has the dimension of μm and v is in μm/s. The tensile strength was recorded 1730 MPa at 25 °C and 1100 MPa at 1200 °C for a fiber crystals grown at a growth speed of 900 mm/h. Eutectic rods having 5 mm of diameter and up to 80 mm in length were also successfully grown by the micro-pulling-down method. The eutectic rods showed 1400 MPa of mechanical strength by compressive mode at 1500 °C with homogeneous colony microstructures.