| Eutectic oxide ceramics prepared by the solidification from the melts exhibit excellent mechanical properties,thermal stability,and oxidation resistance in atmosphere at high temperature.Therefore,they are considered appropriate candidates for ultra-high-temperature materials for aerospace.In particular,the Al2O3-ZrO2?Y2O3?system are marked because of their outstanding mechanical properties with a remarkable strength retention up to nearly the melting temperature and a suitable thermal shock resistance.The phase interface of Al2O3-ZrO2?Y2O3?eutectics played a very important role in the microstructure,orientation relationship?OR?and the grown direction of the eutectics.The ORs of the doped Al2O3/ZrO2 eutectics,of which the low index directions are not strictly parallel,has been defined approximately by the experiments results.?2 1?1?0?A//?0 01?Z and?0 1 1?0?A//?1 0 0?Z is one of the common ORs in this system,the interface is?2 1?1?0?A//?0 0 1?Z.What's more,the OR is deviated to the strict parallel relationship in the range of 0.2°to 2°.However,the analysis of others usually ignore the deviation and the effect of atomic type on interface structure.The crystallographic analysis has been used to calculate the specific OR of Al2O3-ZrO2?Y2O3?eutectics in this work.And the lattice matching is considered of the analysis of the interface matching.Furthermore,the atomic matching is also considered.Firstly,on the basis of the approximate parallel relationship of the eutectics,?g parallelism rule has been applied to get the irrational orientation relationship,[1?7?.?8??9?6.89 0]A//[1 0?0?.?1??3?]Z and[0 0 0 1]A//[010]Z.The quasi-invariant line is[1?7?.?8??9?6.89 0]A/[1 0?0?.?1??3?]Z and the interface orientation is?2?0?.?8??0??1?.?2??0?0?A//?1 0?7?.?8??9??Z.Secondly,based on the OR and the interface orientation,the lattice matching and the atomic matching are considered to confirm the periodic step structure on the interface.The steps are distributed along the quasi-invariant line,the distance between the steps is 2.04 nm,and the height of the step is 2.38?and 2.57?,the lattice plane spacing of?2 1?1?0?A and?0 0 2?Z,which is accordance in the analysis of the lattice matching,the oxygen atoms matching and the metal atoms matching.Finally,CCSL/CDSCL and O lattice theory are adopted to investigate the interface mismatch.The diffraction pattern of the lattice and the atomic structure are utilized to investigate the lattice matching and the atomic matching,because the diffraction condition of the lattice and the atoms are different.At the same time,the CCSL and CDSCL are obtained to calculate the dislocation structure on the interface.There are two set dislocations on the interface,one set is along[0 0 0 1]A/[0 1 0]Z direction,the dislocations are distributed along the quasi-invariant line,and the distance between the dislocations is 2.04 nm,with a burgers vector,61[0 1 1?0]A/41[1 0 0]Z.The other set is along quasi-invariant line,and the distance between the dislocations is 7.67 nm and 1.38 nm,separately,determined by the lattice matching and the atomic matching.The corresponding burgers vectors are115[0 0 0 1]A/61[0 1 0]Z and61[0 0 01]A/21[0 1 0]Z. |
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