SUPERPLASTICITY OF A SiC_w/2024 Al COMPOSITE MADE BY PRESSURE INFILTRATION

The superplastic characteristics of the β-SiC whisker reinforced 2024 aluminum composite, fabricated by pressure infiltration and hot-rolling after extrusion, were investigated. The composite has a fine grain size of about 1μm, and exhibits a maximum tensile elongation of 370% in the initial strain rate of 3.3×10-3s-1 at 788K.The superplastic deformation mechanism of the composite is thought to be grain boundary (interface) sliding accommodated by grain boundary diffusion of aluminum atom and an appropriate amount of liquid phase.     

碳纤维表面电镀铜

研究了碳纤维表面进行镀铜处理的镀液组分及工艺条件。电镀前先在马弗炉中600～800℃下对碳纤维进行氧化处理。镀液采用水浴加热,温度控制在35～40℃,电流密度为0.5～2.5A·dm-2,最佳pH值为9.0±0.5。采用本实验工艺在碳纤维表面镀铜,效率高,镀层均匀,厚度为1.5～2.0μm,基本上消除了“黑心”现象。     

Deposition of cerium contained conversion films on LC4 alloy with square wave pulse method

Cerium contained conversion films were deposited on LC4 aluminum alloy using square wave pulse (SWP) in aCeCl3 solution with KMnO4 as the oxidant. Energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) were adopted to study the composition and the morphology of the film. It is found that the film is composed of Al, Zn, Cu,and small amount of cerium. The polarization curves of the specimens treated with SWP technique measured in 3.5% (mass fraction) NaCl solution reveal that the film thus formed inhibits both the anodic and cathodic process of the corrosion of the specimen. The immersion tests of treated specimens in 3.5% NaCl solution indicate that the corrosion resistance of the SWP treated specimen is better than that of the untreated and is equivalent to or even better than that of the traditionally electro-chemically treated specimens.     

High cycle fatigue and fracture behavior of 2124-T851 aluminum alloy

The high cycle fatigue properties and fracture behavior of 2124-T851 aluminum alloy were investigated roundly, including the fatigue crack growth rate, fracture toughness and fatigue S--N curve. Furthermore, the fatigue crack growth rate was analyzed by fitting the curves. And the microstructure of the alloy was studied using by optical microscopy, transmission electron microscopy and X-ray diffractometry, scanning electron microscop1/2 The results show that the fatigue strength and the fracture toughness of 2124-T851 thick plate are 243 MPa and 29.6 MPa.m at room temperature and R=0. 1, respectively. At high cycle fatigue condition, the characteristics of fatigue facture were observed obviously. And the higher the stress amplitude, the wider the space between the fatigue striations, the faster the rate of fatigue crack developing and going into the intermittent fracture area and the greater the ratio between the intermittent fracture area and the whole fracture area.     

胶凝时间、pH值变化和水玻璃有机酯目硬砂性能的关系

将水玻璃混合液的胶凝时间、pH值变化与水玻璃有机酯自硬砂性能相比较表明：胶凝时间、pH值变化可间接反映自硬砂的性能。     

预氧丝在氧化镁/炭复合材料中的原位碳化及其强化作用

研究了碳纤维前驱体即预氧丝在氧化镁／炭复合材料中原位碳化及其强化作用。在氧化镁／炭复合材料中存在铝、镁添加剂时，预氧丝原位碳化后具有碳纤维的强度和强化效果。预氧丝在添加硅粉的氧化镁／炭材料中原位碳化时因与硅反应失去强度，在无抗氧化添加物的氧化镁／炭材料中原位碳化后，预氧丝因氧化失去强度，对基体无强化作用。     

超声改性水玻璃砂的初步研究

在实验室条件下，较系统地研究了超声改性水玻璃砂的性能。结果表明：超声改性可有效改善水玻璃砂初强度、干强度和溃散姓，且能使水玻璃的加入量由８％降至４％左右。     

AlSi7Mg合金半固态压铸件热处理强化机理研究

对AlSi7Mg合金(A356)半固态压铸件和液态压铸件进行了不同工艺的固溶与时效热处理，分析了其显微组织与疏松度，测定了硬度、拉伸强度及延伸率等力学性能。实验得出，铝合金半固态压铸件原始态的力学性能优于液态压铸件，并且半固态压铸件时效强化效果尤其明显，拉伸强度可达330MPa以上，延伸率10％以上。这主要是由于半固态压铸件比液压件具有更加致密，且为球状的非树枝晶组织。铝合金半固态压铸件时效强化，机理主要归于弥散析出Mg2Si强化相。     

Al2O3/Al基复合材料与基体结合强度物理意义分析

测定了Al2 O3 /Al基复合材料与基体材料间的结合强度 ,探讨了结合强度的物理意义。其物理意义是 :界面抗拉强度与试样达到断裂应变时基体中的应力分别与纤维体积分数和基体体积分数的加权平均值。并根据测定的结合强度的值结合有限元分析得出几种Al2 O3 /Al基复合材料的界面抗拉强度值     

短纤维增强复合材料的仿生模型──Ⅰ 哑铃状短纤维增强复合材料的应力分析

受生物体构件的启发，提出了哑铃状短纤维增强复合材料的模型．分析了带球短纤维和基体中的应力分布，发现端头半径粗化将改善纤维中轴向应力分布，使之趋于均匀化，同时可减少纤维端部界面的剪应力．研究表明纤维长径比对纤维端头应力影响较小．讨论了纤维－基体模量比对纤维轴向最大拉伸应力和界面最大剪应力的影响．