Study On The Preparation And Properties Of Lanxide Ceramic Matrix Composites

The Al2O3/Al composite was prepared by the directed melt oxidation (Lanxide) technique from Al-5Zn-10Si alloy at 1100℃in air, and the structure evolvements during aluminum alloy oxidation growth process were observed by TG analysis and abortive growth experiments. ZnO, MgO and SiO₂ powders were covered on top of the alloy as dopants, the effects and principles of the dopants were discussed. Based these, SiC particles were made into preforms with different distribution of air holes by changing the granularity of SiC particles and the content of graphite additive, and the oxidation growth of aluminum alloy melt into the air holes within the preform was controlled to prepare SiC/Al₂O₃/Al composite with inerratic shape. And the SiC particles effect principle to the oxidation of SiC/Al2O3/Al composite was studied. The composites were analyzed by XRD, SEM and microstructure observes, and the erosion wear behavior and thermal shock resistance were carried on respectively by the slurry test rig and indentation-quick cooling method, then the reinforce principles of SiC particles were discussed.It was found that there are three periods during the directed oxidation growth of Al-5Zn-10Si alloy, which are the incubation period, rapid growth period and the complete period. The structure changes obviously in each period. The Al₂O₃/Al composite follows a typical growth way of cellular macrostructure, and the microstructure is composed of three-dimensional continuousα-Al2O3 phase as the framework, and among it there are the re mnant Al-Si and air holes.Using ZnO, MgO or SiO₂ powder as external dopant, the oxidation growth incubation period of aluminum alloy is shortened obviously, the oxidation growth speed increases, thegrowth way of the composite is improved, and the density and uniformity of the composite become better. By introducing the SiC preform, the oxidation growth incubation period of Al-Si-Zn alloy is shortened, the volume stability of SiC/Al₂O₃/Al composite is good, and the structure uniformity and density are fine.Because of the"shadow effect"and"support effect"between SiC particles and Al2O3 matrix, the erosion wear behavior of the SiC/Al₂O₃/Al composite is excellent. And due to the thermal dilatabilities of SiC particles and Al₂O₃ matrix are ill-matched, a lot of energies are consumed by the cracks deflexion during the heating-quick cooling process, so the SiC/Al₂O₃/Al composite shows a good thermal shock resistance.