Effects of Ag addition on mechanical properties and microstructures of Al-SCu-0.5Mg alloy

The mechanical properties and microstructures of Al-8Cu-0.5Mg alloy with and without Ag addition were studied at both room- and elevated-temperatures. The results show that the alloy with Ag is strengthened by a homogeneous distribution of coexistent θ＇ and Ω precipitates on the matrix （001） and （111） planes, respectively, whereas the alloy without Ag by θ＇ precipitates only. The small size and high volume fraction of θ＇ and Ω precipitates in the Ag-containing alloy improve the tensile strength and yield strength, especially those at the elevated temperatures. However, it is also responsible for the decrease in elongation, compared with the alloy without Ag, which is due to the microcracks initiated from the inherent incompatibility between the particles and the AI matrix during deformation.     

纳米掺杂Ag（SnFe）O2电接触合金的研究

利用化学共沉淀、高能球磨技术及热压烧结等方法制备出纳米掺杂Ag（SnFe）O2触头合金，通过X射线衍射（XRD）、透射电镜（TEM）和冷场发射扫描电镜（FESEM）等对合金触头及其燃弧性能进行了分析。结果发现：Fe元素的加入，使Sn02纳米颗粒在550℃以下焙烧制粉和750℃以下块体烧结成型时都未明显长大，保持在20nm左右，制备的触头合金呈现纳米第二相弥散均匀分布在Ag基体中。在模拟电弧侵蚀试验中，该合金电弧阴极斑点铺展在较大区域，形成多点燃弧形貌，有效降低燃弧时间和电弧电流，分散电弧能量，使阴极斑点没有明显的液体喷溅、Ag的蒸发和第二相的分解，同时非晶的纳米第二相与Ag的润湿性更好，可进一步增加熔体粘度，提高耐电弧侵蚀性能。     

低碳低合金铸钢力学性能的研究

利用Olympus光学显微镜、扫描电镜(SEM)及能谱分析(EDAX)探讨了等温淬火工艺对低碳低合金CrMnSi铸钢力学性能的影响,并通过XRD定量分析了相的组成.结果表明,合适的等温淬火工艺,可获得一定数量的贝氏体和残余奥氏体(约6%)的复合组织,冲击断口形貌由解理刻面变为韧窝状,铸造成形无缺口试样(10 mm×10 mm×55 mm)的冲击韧度由ακ≤30 J/cm2增加至ακ≥170 J/cm2,硬度HRC≥40,具有较高硬度和冲击韧度的配合.     

光亮碱性Zn-Al合金电镀工艺研究

在碱性锌酸盐镀锌液中加入铝盐，研究成功了一种光亮碱性锌铝合金电镀工艺。采用霍尔槽试验探讨了镀液成分和工艺条件对镀层质量的影响，检测了镀液和镀层性能。研究结果表明：镀液阴极电流效率达到80%以上，镀液分散能力和复盖能力好，镀层中铝含量为1．5％左右，所形成的Zn-Al合金镀层结晶细致、光亮度好、结合力好、耐蚀性优良，适用于作高耐蚀性镀层。     

Effect of electric pulse treatment on solidification structure of an A1-15%Si alloy

The effect of electric pulse modifying on the solidification structure of an Al-15%Si alloy was investigated. The result shows that the primary silicon disappears sometimes and the eutectic phase is refined after the treatrnent of EP （electric pulse） though there are different modalities in different treating durations. DSC （differential scanning calorimetry） analysis indicates that the super-cooling texture decreases and the freezing range narrows evidently after the electric pulse treatment.     

Al-Ti-C对纯铝晶粒细化效果的研究

添加本院研制的Al Ti C中间合金,通过对细化条件的调整和控制,使工业纯铝的平均晶粒度降低到96μm,且时间延长到2h后平均晶粒度仍在110μm左右。表明本院研制的Al Ti C中间合金具有优异且稳定的细化作用。     

Ti-22Al-25Nb合金ISM熔炼过程中的成分控制

采用X荧光光谱(XRF)分析水冷铜坩埚真空感应炉熔炼(ISM)加入和不加入稀土Y的Ti-22Al-25Nb合金铸锭成分,分析结果表明,在保证获得成分均匀的合金铸锭的情况下,Al的挥发烧损在28.94%～33.88%之间;加入at为0.5%～1%Y,Y的挥发烧损在w为17.20%～34.26%;采取提高熔化温度降低保温时间的措施可以降低Al的挥发烧损.     

Aging Behavior of Cu-Cr-Zr-Ce Alloy

The aging properties of Cu-0.35Cr-0.038Zr-0.055Ce alloy are studied. The results show that can obtain higher electrical conductivity and microhardness after solutioned at 920℃ for lh, and aged at 500℃. The process of precipitation of the secondary phase can be accelerated with cold deformation before aging, so properties of the alloy are improved.Upon aging at 500℃ for 30 minutes after 60% cold deformation, the values of electrical conductivity and microhardness are 69.0%IACS and 152HV respectively, but they are only 66.2%IACS and 136HV upon directly aging after solution. With the addition of a trace of rare earth element Ce, the value of microhardness of Cu-0.35Cr-0.038Zr alloy increases 18～25HV,while the value of electrical conductivity drops a little.     

Microstructures and evolution mechanism of highly undercooled Ni-Pb hypermonotectic alloy

The microstructures and evolution mechanism of the undercooled Ni-20%Pb(molar fraction) alloy were investigated systematically by high undercooling solidification technique. The experiment results indicate that the morphology of α-Ni phase and the distribution of Pb element in undercooled Ni-20% Pb alloys change with the in-crease of undercooling. The main evolution mechanisms of α-Ni are dendrite remelting and recrystallization. Pb phase in the microstructure of Ni-20% Pb hypermonotectic alloy originates from L2 phase separated from the parent melt during the cooling process through immiscible gap and L2 phase formed at the temperature of monotectic trans-formation. The solubility of Ph element in α-Ni phase under high undercooling condition is up to 5.83% which is ob-viously higher than that under equilibrium solidification condition. The real reason that causes the solubility difference is distinct solute trapping.     

Amorphous sol-gel SiO2 film for protection of Ti6Al4V alloy against high temperature oxidation

Amorphous SiO₂ thin films were deposited on Ti6Al4V alloy by sol-gel processing. Isothermal and cyclic oxidation tests of the coated and uncoated specimens were performed at 700 and 800 °C. The SiO₂ film exhibited beneficial effects on the oxidation resistance of the alloy. Titania scales formed on the uncoated specimens, and severe spallation and stratification of the scales were observed. The oxidation rates of the silica coated specimens were decreased significantly. The silica film shrunk to about a quarter in thickness, probably by mechanism of crystallization of silica and evaporation of the organic additments. The oxide scales formed on the coated specimens were multilayered. Beneath the silica film, formation of a thick rutile titania layer followed by a thin alumina layer occurred. Above the silica film, alumina plus minor titania layer formed. It is deduced therefore that the growth of the multilayered and mixed oxide scales was dominated by both outward diffusion of metal and inward diffusion of oxygen.