Structure and tensile／wear properties of microarc oxidation ceramic coatings on aluminium alloy

Thick and hard ceramic coatings were prepared on the Al-Cu-Mg alloy by microarc oxidation in alkali-silicate electrolytic solution. The thickness and microhardness of the oxide coatings were measured. The influence of current density on the growth rate of the coating was examined. The rnicrostructure and phase composition of the coatings were investigated by means of scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Moreover, the tensile strength of the AI alloy before and after microarc oxidation treatment were tested, and the fractography and morphology of the oxide coatings were observed using scanning electron microscope. It is found that the current density considerably influences the growth rate of the microarc oxidation coatings. The oxide coating is mainly composed of α-Al2 O3 and γ-Al2O3, while high content of Si is observed in the superficial layer of the coating. The cross-section microhardness of 120μm thick coating reaches the maximum at distance of 35μm from the substrate/coating interface. The tensile strength and elongation of the coated AI alloy significantly decrease with increasing coating thickness. The rnicroarc oxidation coatings greatly improve the wear resistance of AI alloy, but have high friction coefficient which changes in the range of 0.7-0.8. Under grease lubricating, friction coefficient is only 0. 15 and wear loss is less than 1/10 of the loss under dry friction.     

铸件热节变化与冒口位置的分析

热节是铸件凝固慢的节点或区域,可分为几何热节、物理热节、接触热节和流动热节.热节的位置、大小受铸件结构、铸型材质和浇冒口系统的开设位置所影响.冒口的开设应使接触热节、流动热节与几何热节分离.     

铸造高合金不锈钢在稀硫酸水砂介质中的冲刷腐蚀行为

采用电子探针和扫描电镜等手段研究了不同成分Cr-Ni-Mo合金对铸造高合金不锈钢金相组织的影响，采用自制的冲刷腐蚀试验机比较了不同Cr-Ni-Mo成分高合金不锈钢和25．20不锈钢在模拟的强冲刷弱腐蚀介质条件（0．1MH2SO4＋10％si02）中的冲刷腐蚀行为。结果表明，Cr、Mo合金元素促进组织中σ相的析出，Ni抑制σ相的析出；高合金不锈钢的冲刷腐蚀特征均表现为纯冲刷作用为主，腐蚀为辅，同时腐蚀与冲刷之间有很强的交互作用；or相没有降低高合金材料的耐蚀性，但明显提高了其抗冲刷腐蚀性能。     

铝合金表面等离子喷涂Al2O3-3%TiO2复合涂层工艺参数优化的研究

目的 通过优化等离子喷涂工艺参数，提高铝合金表面等离子喷涂Al2O3-3%TiO2复合陶瓷涂层的结合强度和涂层表截面硬度。方法 用正交试验法，对影响喷涂涂层结合强度和硬度的4个关键喷涂参数进行优化，分别得到喷涂粘结底层Ni-5Al和工作表层Al2O3-3%TiO2的最佳优化参数。结果 通过正交试验确定影响Ni-5Al涂层综合指标的因素由主到次是喷涂电流、喷涂距离、辅气流量、主气流量，最优水平数为2、3、2、1；影响Al2O3-3%TiO2涂层综合指标的因素由主到次是喷距、辅气流量、电流、主气流量，最优水平数为2、3、2、1。Ni-5Al涂层的最佳喷涂工艺参数为：喷涂距离120 mm，喷涂电流520 A，主气流量42 L/min，辅气流量7.5 L/min。Al2O3-3%TiO2复合涂层最佳喷涂工艺参数为：喷涂距离90 mm，喷涂电流530 A，主气流量46 L/min，辅气流量7.8 L/min。最佳工艺下制备的Ni-5Al底层与基体的结合强度为25.2 MPa，Al2O3-3%TiO2复合涂层与Ni-5Al底层的结合强度为17.8 MPa，且其截面硬度在1000HV0.5以上。结论 对喷涂工艺参数进行优化可以得到质量高且稳定的Al2O3-3%TiO2复合喷涂涂层，与非最佳工艺参数喷涂涂层相比，各指标均有较大提高。     

AN APPLICATION OF SPI TECHNIQUE FOR STUDING STRA DISTRIBUTION AT CRACK TIP

A computerized digital speckle-interferometry(SPI)system has been set up to determinethe in-plane distribution of displacement and strain at crack tip of CF specimens.Theprinciple and the experimental method of this technique are described in detail.Theeffect of corrosion factors on plastic deformation at crack tip in CF process has beenexamined by comparing the near-tip strain fields of steel A537 before and after hydrogencharging,and of pure copper before and after applying an anodic current in 3.5% NaCl.The results shows that the clasic finite element mathematical models are not suitable todescribe the near-tip deformation under the experimental conditions.Hydrogen chargingmade the crack tip plasticity decreased for steel A537 and the anodic dissolution enhancethe near tip deformation of pure copper specimen.     

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 文章分析了连铸坯表面纵向裂纹的成因，并提出与化学成份和保护渣质量有很大关系。     

板式降膜蒸发器自控系统中存在的问题及改进

中铝山西分公司的板式降膜蒸发器投产以来，控制系统运行平稳。但在运行中也暴露出一些问题：该系统保护连锁存在缺陷；现场主要一次仪表的腐蚀损坏严重，威胁设备的稳定运行。本文针对存在的问题。进行分析提出解决的方案。并且对瑰场仪表提出了几种保护措施。     

潭水河流域预报方案构建探索

针对潭水河流域荆山水文站,首先进行了暴雨洪水特点及难点分析,介绍适用的新安江模型、单位线法、降雨径流相关法3种方法的原理及适用条件,然后通过应用以上3种方法建立潭水河荆山站洪水预报方案,使用201415"海鸥"暴雨径流过程进行方案检验。分析结果表明,荆山站资料齐备,使用新安江模型预报更为可靠。     

小型水电站电气自动化应用探讨

随着计算机技术的快速发展及自动化控制技术的日趋成熟,水电站电气自动化控制逐步得到应用。本文对古黄河水利枢纽水电站自动化控制系统进行介绍,该系统实现了电站的现代化管理,节约了人员成本,提高了工作效率,确保了水电站安全经济运行。     

五元系数法-改进熵权法在水质评价中的应用

为了使水质监测值和水体划类标准值之间关系更紧密,利用五元联系数方法建立了各水质评价指标与评价标准的五元联系数;同时在传统熵权计算的基础上,采用秩比法设定偏好校正系数,得到改进的熵权重;最后将五元联系数ui和改进的熵权重WRi相结合获得五元综合联系度,据此对水质进行评价,这是一种主客观结合的、符合实际情况的水质评价新方法。以贵州贵阳市河流断面监测数据为例,评定样本点所在河段水质等级,分析了该河流水质变化趋势,验证了五元系数法-改进熵权法水质评价方法的实用性。