Predicting model on ultimate compressive strength of Al_2O_3-ZrO_2 ceramic foam filter based on BP neural network

In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template （F）, centrifugal acceleration （v） and sintering temperature （T）, while the only output was the ultimate compressive strength （（7）. According to the registered BP model, the effects of F, v, T on 0 were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.

Theoretical Analysis on Tensile Strength of ZA22/Al_2O_3 Short Fiber Composite Added with Ce

The tensile strength of squeeze casting ZA22/Al 2O 3 short fiber composite was measured with autograph AG 10TA universal testing machines made in Japan. The experimental results were analysed with the rule of mixture(ROM) model modified by Friend. The theoretical analysis agree well with the experimental results. Under the test condition of this study, the strengthening critical fiber volume fraction predicted is 34 5%. Because fiber volume fraction in the composite is under this value, the tensile strength of the composite is lower than that of ZA22 alloy matrix.

Preliminary Study on Combining K2O-Al2O3-SiO2 System Dental Glass Ceramic with Al2O3 Ceramic

Relationship between K2O-Al2O3-SiO2 system dental glass ceramics and Al2O3 ceramics was investigated. 4 groups of glass ceramic with the same components but different thickness（0.8, 1.2, 1.6, and 2.0 mm） were sintered on Al2O3 base ceramics according to the same thermal treatment system of leucite micro-crystallization reported in previous literatures. The products of each group were analyzed by polarizing microscope, X-ray diffractometer, and an INSTRON material testing machine. Under the thermal treatment system, leucite crystals were formed in samples of each group, and dispersed evenly. Meanwhile, the compressive strengths of group 3 and group 4 were higher than those of group 1 and group 2. Samples of group 3 showed better mechanical properties than others. The conclusions are drawn that Leucite crystals can be controlled in K2O-Al2O3-SiO2 system glass ceramic-Al2O3 ceramic composite material, and the thickness of glass ceramic has a notable influence on the compressive strength of this ceramic composite material.

Alumina/Polyimide Composite Porous Nanosolid:Dielectric Characteristics and Compressive Strength

Al2O3 porous nanosolid was prepared via solvothermal hot-press（SHP） method.The dielectric constant of Al2O3 porous nanosolid is as low as 2.34,while its compressive strength is very poor.In order to improve the compressive strength and maitain low dielectric constant,polyimide was introduced to prepare Al2O3 /polyimide composite porous nanosolid.Compared to Al2O3 porous nanosolid,Al2O3 /polyimide composite porous nanosolid possesses much higher compressive strength,which reaches its saturation value when the mass loading of polyimide is 7.75%.In addition,the in situ Fourier transformation infrared（FTIR） monitoring result reveals that Al2O3 /polyimide composite porous nanosolid is stable up to 400 °C.

7A52铝合金封接Al2O3陶瓷工艺

采用钎焊对7A52铝合金和直径∅10 mm表面镀镍的氧化铝陶瓷球进行封装,研究了加热温度和保温时间对显微组织特征、特征点成分和抗剪强度的影响。结果表明,采用硅镁焊料的7A52铝合金和Al 2 O 3(Ni)陶瓷封接的最佳工艺参数:加热温度为590℃,压力2 MPa,保温时间1 h,反应层厚度在10~27μm,接头达到的最大抗剪强度为24.8 MPa,接头界面结构为Al 2 O 3陶瓷/Al-Ni金属间化合物/Al-Si共晶/7A52铝合金。

Fabrication of Aluminium Matrix Composite Using Thixoforming Process for High Strength Material Components

Aluminium-based MMCs(metal matrix composites)have many potential applications in the automotive manufacturing industry,aerospace and military because the aluminum has a low density.Aluminum as a matrix with Al2O3 reinforcement has attracted interest to be developed in order to improve the mechanical property.The study carried out the formation of Al-5%Cu-4%Mg matrix with the reinforcement of Al2O3 by thixoforming process.In this paper,we studied the effect of semisolid thixoforming process on strength of Al-5%Cu-4%Mg matrix.The matrix used here was doped by Al2O3 with the volume fraction from 5%to 20%.It is found that strength of MMCs significantly increases with increasing volume fraction of Al2O3 reinforcement from 5%to 20%.This is due to a good wettability in interface region such as formation of spinel MgAl2O4 phase.Moreover,toughness of MMCs increases by process of semisolid thixoforming due to evolution of microstructure such as globular and fine grain structures.These results indicate that the thixocasting process conducted in this study could increase the value of the matrix hardness and tensile strength,so that such process opens up opportunity for application in the manufacturing industry.

Effects of Y_2O_3 on Thermal Shock of Al_2O_3/TiCN Composites

Thermal shock resistance of Al2O3-TiCN(30%)-Y2O3(0.2%) composite was studied by hot pressing(HP) method at different temperatures. The study shows that thermal shock resistance of the material is determined by its microstructure and reinforced mechanism. According to SEM and calculation of thermal shock, the fractured surface of Al2O3-30%TiCN-0.2%Y2O3 composite is undulate. The residual strength of Al2O3-30%TiCN-0.2%Y2O3 is higher than Al2O3-30%TiCN at 200～800 ℃ after thermal shock. Cracks initiation resistance (R′)and cracks propagation resistance (R″″)of Al2O3-30%TiCN-0.2%Y2O3 composite increases 12% and 5% respectively compared with that of Al2O3-30%TiCN. It matches with experimental results. The addition of Y2O3 forms YAG that inhibits crystal growth, and increases fracture stress, fracture toughness, cracks initiation resistance and cracks propagation resistance. Therefore, thermal shock resistance increases. The fracture work of Al2O3-30%TiCN and Al2O3-30%TiCN-0.2%Y2O3 composites are 132 and 148 J·m-2 respectively.

Oxidation of Al_2O_3-30%TiCN-0.2%Y_2O_3 Composite

The oxidation behavior of Al2O3-30%TiCN-0.2%Y2O3 composite and its effect on high temperature bending strength was studied. The result indicates that the mass gain during static oxidation of the material under normal atmosphere follows the parabolic law. Oxide increases with increasing temperature and prolonging time. It has good oxidation resistance. The product of oxidation of the material is TiO2. Therefore, the volume of the material expands. The oxide film is destroyed because residual stress inside the oxide film is released. Proper oxidation is beneficial to the improvement of bending strength of Al2O3-30%TiCN-0.2%Y2O3 composite. The strength increase is up to 4.5%.

用Y_2O_3Al_2O_3SiO_2Si_3N_4钎料连接氮化硅复相陶瓷

研究了用Ｙ２Ｏ３Ａｌ２Ｏ３ＳｉＯ２Ｓｉ３Ｎ４ 钎料对氮化硅复相陶瓷的连接． 对连接界面进行ＳＥＭ、ＥＰＭＡ和ＸＲＤ分析．接头强度随着保温时间、连接温度的增加而逐渐增加． 在达到峰值后，连接强度逐渐降低．在ＹＡＳ钎料中添加氮化硅， 可以降低接头界面的热应力，改善接头强度． 微观分析表明：接头强度的变化主要与界面反应和界面孔洞损伤有关．

THE STUDY ON BEHAVIOR OF Al_2O_3-C BRICK FOR BLAST FURNACE AT HIGH TEMPERATURE

In experimental conditions simulating reducing atmosphere in Blast Furnace, the samples of Al 2O 3 C brick were heated at high temperature. Their microscopic structures were observed by Scanning Electric Telescope and rupture and compressive strength measured before and after heating observed the changes. According to these measurements, the reasons causing the changes were analyzed.

Multilayer aluminum composites prepared by rolling of pure and anodized aluminum foils

Experimental results on processing,structural and mechanical characterization of a multilayer composite based on commercially pure aluminum foils were presented.A multilayer composite was produced by hot-rolling of anodized and non-anodized aluminum foils alternately sandwiched.In addition,the same process was applied for bonding of non-anodized foils.In both cases,obtained multilayer composites were compact and sound.In order to study composites microstructural evolution and mechanical properties,optical and scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),X-ray diffraction(XRD)analysis,hardness,tensile and three-point flexural tests were performed.Microstructural characterization confirmed that the rod-like particles distributed in parallel rows in the composite aluminum matrix with anodized foils correspond to Al2O3.Maximum and minimum peaks of oxygen and aluminum,respectively,suggest that after the final hot-rolling of composite with non-anodized foils,a small amount of coarser particles were formed at boundaries between foils.Hardness,strength,modulus of elasticity and flexural strength of both multilayer composites were much higher than those of pure aluminum,whereas ductility was significantly less.The composite with anodized foils exhibited the highest strength and modulus of elasticity,but lower ductility compared to composite processed from non-anodized foils.Fracture failure corresponded to the change of ductility.

Al_2O_3-SiO_2纤维增强ZL109合金复合材料的强度特性

用低成本的Ａｌ２Ｏ３－ＳｉＯ２系纤维作为增强相，通过加压铸造法制作ＺＬ１０９合金复合材料，并对该复合材料（Ｖｆ２０％）和ＺＬ１０９合金进行不同温度下的时效处理和压缩试验．通过ＤＳＣ和ＴＥＭ分析认为：复合材料中的基体具有和ＺＬ１０９合金一样的时效硬化特性，所以纤维对ＺＬ１０９合金的增强效果明显．在高温下或在高温下长期保温后的基体材料中时效硬化作用消失，所以纤维的增强作用更为显著．