| Alumina ceramic materials having become a kind of being widely used and most needed materials because their excellent properties,such as higher strength,higher hardness,higher temperature resistance,higher corrosion resistance and higher chemical stability.However,some common problems,such as fragihty nonuinformity,lower heat shock ability and worse fracture toughness property,have been found during their untility.Up till now,there are many way to improve the properties of ceramic materials;for example,changing sintering technique,toughening by adding second fase,improving by adding other particles or crystal whisker or modifying by coating some metals and so on.These methods above also can bring some other issuts accompanying their improving the Al2O3 ceramic materials yet,as inducing brittlences or reducing purity as well.As for crucible material for high purity aluminum alloyes smelting,high purity crucible is used generally,but it cataclastic corundum failure severely caused by heat shock as its being used in the condition of heat up and cooling down sharply.Aim at this question,this article studied the technology for preparation AI/Al2O3 cermet frome power metallurgy and oxidation sintering technology,thus is,by using A1 and Al2O3 powder as raw material,mixing and grinding,model and sintering to fabricat the Al/Al2O3 ceramic materials.The metal Al will be oxided to form integrated Al2O3 ceramic with the Al2O3 added in raw material;the remaining Al will be as binding agent between the Al2O3 ceramoc grains and preventing the Al2O3 ceramic combing to from airew crystalisation,so as to improve the strength and heat shock properties.This article studied the composition of the Al and Al2O3 powder,mixing and grinding,the condition of modeling,the technology of sintering technology systemically.The results of these researchs are obtained as follow:(1)The composition of the raw materials has great influence on the material performance and microstrucfure,and the low aluminum content can cause the maternal tissues loose and low strength,due to its lack of adequate oxidation activity in the blank;in the other hand,the too high aluminum confent will can not be oxidation completely.The content of Al/Al2O3 cermet is suitable in the range of 30wt.%?60wt.%.(2)The porosity,mechanical property and microstrucfure analysis shwed that:the sintering temperature to preparation the Al/Al2O3 cermet by using Oxidation-Sintering technology can not lower than 1100?,the sintering time has great influence on the microstrucfure of the materials and the time 4h will conducire to the growth of grain and shrinkage of porose,so that the infernal structure of the material is homogeneous.The heat rafe also affects the microstrucfure of the material,and the rapidly heating rate during the low temperature is favord for growth of the crystal and the contraction stomafa.(3)The oxidation rate of the metal Al contained in the sample preliminarily evalnated;and the influence of the sintering temperature on the oxidation was found when the temperature below 1300?,the oxidation rate of Al is significantly quick rate of the specimen with the Oxidation-Sintering time is identical regression cure,when the sintering temperature is during 1000 ??1450?.(4)The test results showed that the sample having no significant change after 35 repeatedly hot shock.The bending strength value of the sample after being treated 35 times is 70.4%prior to processing and this result suggest that the Al/Al2O3 cermet material preporaed metallurgy-Oxidition-Sintering technology behaves good hot shock proportion.Accoding to performance analysis,this material can take place of the traditional high pure alumina crucible for the smelting of high purity aluminum alloy. |
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