Tensile and bending behavior of melt growth Al₂O₃/YAG composite at ultra high temperatures (1773-2023K)

The deformation and fracture behavior at 1773-2023K of the unidirectionally solidified eutectic Al₂O₃/YAG (Yttrium-Aluminum Garnet with the composition of Y₃A₁₅O₁₃) ceramic composite was investigated. The stress-stain curve and strength of unnotched and notched specimens, measured by bending and tensile tests, showed that (a) both unnotched and notched specimens fractured in a brittle manner at low temperatures and at high displacement speeds, but in a ductile manner at high temperatures and at low displacement speeds, and (b) the notched strength increased, reaching maximum, and decreased with increasing temperature and decreasing displacement speed. The increase in the notched strength with increasing temperature and decreasing displacement speed up to the maximum value was accounted for by the increase in plastic zone size ahead of the notch, and the decrease with further increasing temperature and decreasing displacement speed by the loss of the stress carrying capacity of the yielded ligament, based on the finite element analysis.