石墨烯含量对Al-15Si-4Cu-Mg组织及摩擦磨损性能的影响

利用金相显微镜(OM)、摩擦磨损试验机、扫描电镜(SEM)对Al-15Si-4Cu-Mg复合材料微观组织形貌、摩擦磨损性能、磨痕表面形貌进行表征和分析。研究添加不同含量石墨烯对Al-15Si-4Cu-Mg复合材料微观组织及摩擦磨损性能的影响。结果表明,随石墨烯含量增加,复合材料中硅颗粒形貌逐渐变得圆钝且尺寸减小,复合材料的硬度有所增加,摩擦系数减小,耐磨性能显著提高;加入0.3%石墨烯的复合材料磨损机制为磨粒磨损,当石墨烯的含量达到0.7%时复合材料的磨损机制以轻微的粘着磨损为主并有少量的磨粒磨损。     

Cu对Al-15Si合金的高温摩擦磨损行为的影响

研究了Al-15Si-xCu合金高温(400℃)摩擦磨损行为.采用Pandat软件计算了Al-15Si-xCu系合金平衡相图.利用光学显微镜和扫描电镜研究了Al-15Si-xCu系活塞合金不同铜含量下400℃摩擦磨损行为.研究结果表明:活塞合金经T6热处理后,随着Cu含量的增加,摩擦因数逐渐减小,磨损失重量减少,其高温耐磨性能得到明显提高;w(Cu)含量为4.5和5.5时,活塞合金的摩擦磨损性能差异较小,这与合金中高温稳定相(Q相、ε相、θ相)密切相关;w(Cu)含量为2.5和3.5的活塞合金,其磨损机制主要是粘着磨损,而对于w(Cu)含量为4.5和5.5的合金,其磨损机制主要是磨粒磨损.     

Mg-8Zn-4Al-0.3Mn-xRE合金的时效析出过程及其动力学

采用金相显微分析和DSC分析了Mg-8Zn-4A1-0．3Mn-x RE含金时效析出过程及其动力学，结果表明，未添加RE元素的Mg-8Zn-4A1-0．3Mn合金的时效析出过程为：过饱和固溶体→细小弥散析出相→再结晶软化和析出相的聚集长大；添加RE元素的Mg-8Zn-4A1-0．3Mn合金的时效析出过程为：过饱和固溶体→细小弥散析出相→析出相的聚集长大．人工时效后，与未加RE的合金相比，合金2，3，4显微硬度峰值提高分别达5．6％，9％，13．4％；随着RE元素含量的增加，合金的析出相形成激活能呈逐渐增大的变化规律．     

石墨铝复合材料的研制及摩擦磨损

本文叙述了一种制备共晶型铝硅合金-石墨颗粒复合材料的方法,即采用盐溶液对石墨颗粒进行预处理。通过液体旋涡技术将石墨颗粒加入到共晶型铝硅合金中;对石墨铝复合材料在无润滑条件下的磨损特性进行了研究,探讨了法向载荷、滑动速度及复合材料中的石墨含量对石墨铝复合材料摩擦系数和磨损速率的影响。     

三元Pb-Sb-Sn合金的快速凝固及组织特征

实现了三元Pb-12%Sb-4%Sn和Pb-15%Sb-10%Sn合金在深过冷条件下的快速凝固,实验中获得的最大过冷度分别为65 K(0.13TE)和70 K(0.13TL)。XRD分析表明,这两种合金在实验过冷度范围内均由(Pb)固溶体、(Sb)固溶体和SbSn金属间化合物三相组成。在小过冷条件下,Pb-12%Sb-4%Sn共晶合金的三相以层片状交替分布,协同生长。随着过冷度增大,(Sb)作为初生相以小平面方式生长,且三元层片共晶组织显著细化。对于Pb-15%Sb-10%Sn合金,其凝固组织由初生相、二相共晶和三元共晶组成,初生SbSn相以具有小平面特征的枝晶方式生长。在实验基础上,对三元Pb-Sb-Sn合金的形核特征和生长规律进行了理论分析。     

Fe-2.3Si-3.7C合金中渗碳体的石墨化

为了探索白口铁的石墨化机理,研究了Fe-2.3Si-3.7C合金中石墨化形核及长大过程.通过电子显微分析、光学金相分析发现,石墨可以在奥氏体中、渗碳体中、渗碳体/奥氏体的相界面上形核,但在奥氏体中的形核几率最大.石墨化形核速度很快,硅在渗碳体的石墨化过程中起到异乎寻常的促进作用.渗碳体的石墨化是通过渗碳体溶解、熔断,碳原子长程扩散,石墨形核并且不断长大的过程.     

微量元素对特殊黄铜组织和耐磨性能的影响

利用电子探针、磨损试验机等试验手段，研究了微量元素对特殊黄铜的组织和耐磨性能的影响．结果表明，微量元素的加入可以提高α相的数量，促使耐磨质点Mn3Si3的形成，调整α相及Mn5Si3质点的形态、分布、大小，在摩擦磨损过程中这些变化有利于阻止裂纹形核和扩展，同时微量元素的加入可以在磨损区的表层形成致密的氧化物或微量元素的化合物，减轻粘着磨损，从而提高材料的耐磨性．     

原位合成V8C7颗粒增强铁基复合材料的结构和性能

利用粉末冶金技术,在真空状态下使（Fe-V合金+石墨）体系进行碳化反应原位合成V8C7铁基复合材料,采用SEM和XRD分析复合材料的组织结构和相组成,用MM200磨损实验机对复合材料进行耐磨性实验。探讨原位合成V8C7的机理。结果表明,石墨的存在降低了σ-（FeV）相的稳定性,促使其在1073 K就分离出少量α-Fe相和金属V。此复合材料主要由增强相V8C7和α-Fe相组成,在重载干滑动磨损条件下显示出很好的耐磨性能。     

短纤维增强铝硅合金梯度复合材料耐磨性能的研究

采用挤压铸造技术制备短纤维增强铝硅合金梯度复合材料,研究了这类材料的凝固组织和耐磨性能.结果表明,在复合材料中,基体组织细小,纤维与基体结合良好,并呈梯度状无序分布;梯度复合材料的耐磨性能优异.     

低温低压下石墨对金刚石钻头胎体摩擦性能的影响

为了更加科学地设计低温低压无冲洗介质条件下的金刚石钻头胎体,基于金刚石钻头干钻时出现高温摩擦热的现象,采用向胎体中添加石墨作为润滑剂的方案,以减小胎体的摩擦因数,降低摩擦热.研究石墨的体积分数、粒度对胎体力学性能和不同环境下对胎体摩擦性能的影响,结果表明:随着石墨体积分数的增加,胎体的硬度,抗弯强度,常温常压、低温低压下的摩擦因数逐渐减小,磨损量先减小后增大,当石墨体积分数增加到7.5%时,磨损量达最小值.随着胎体中石墨粒度的减小,胎体的抗弯强度和常温常压、低温低压下的摩擦因数逐渐减小,胎体的硬度和磨损量逐渐增大.摩擦磨损后胎体的形貌分析表明,加入石墨后,胎体在不同环境下的磨损均减轻,可实现对钻头胎体的润滑作用.     

过共品铸造Al-Si—Cu—Mg—Fe合金组织性能研究

通过正交试验和单因素试验,考察了Cu、Mg、Zn、Ni和Fe对Al—18Si过共晶铝硅合金室温及高温（350℃）力学性能的影响规律,利用光学金相显微镜（OM）、扫描电镜（SEM）、能谱分析仪（EDX）对合金中富Cu相、富Fe相的组织组成进行了分析．结果表明：Cu、Mg是提高AI-18Si过共晶铝硅舍金室温及高温强度的主要因素;Zn含量增加明显降低合金350℃时的高温强度,改善合金的室温和高温延伸率;Fe降低合金的室温强度,显著提高合金的高温强度;当Cr：Fe=0．35：1,Mn：Cr=2：1,含铁0．8％～1．2％时,Al-18Si-4．0Cu-0．7Mg-0．2Zn-1.0Ni-（0．8～1．2）Fe合金力学性能σb（25℃））310MPa,延伸率受（25℃）≥0．75%,σb（350℃）〉130MPa,延伸率δs（35℃）〉1．5％;合金中富铜相主要以块状Al。Cu相和白灰色花卉状A15Si。cu2Mg8相存在,富铁相主要以三叶草状、树枝状和棒状Al5Si（Cr,Mn,Fe）相存在．     

Cu含量对汽车车身板用Al-1.0Mg-1.0Si-0.6Mn合金显微组织的影响

采用金相、SEM/EDS、XRD等研究了Cu含量对汽车车身用Al-1.0Mg-1.0Si-0.6Mn（in wt.%）铝合金结晶相及合金板材晶粒的影响规律.结果表明：Al-1.0Mg-1.0Si-（0.1~0.7）Cu-0.6Mn合金中主要存在部分可溶的浅灰色不规则条块状Al8（FeMn）2Si和黑色条块状或骨骼状结晶相Mg2Si,及完全可溶的球状或椭球状主要含Al1.9CuMg4.1Si3.3多相共晶产物;随着Cu含量增加,铸态合金中主要含Al1.9CuMg4.1Si3.3的共晶产物数量逐渐增多,而Mg2Si和Al8（FeMn）2Si结晶相变化不明显;同时,固溶后合金板材的再结晶晶粒变得越来越细,尽管Cu含量对合金冷轧板的晶粒尺寸影响不明显.     

熔体温度处理对磷铜变质Al-20%Si组织的影响

研究熔体温度处理工艺（包括熔体混合及熔体过热处理）与磷铜变质对Al-20%Si合金中硅相形态的影响。结果表明：在本试验条件下,单纯添加磷铜变质剂的Al-20%Si合金,当添加其合金质量的0.4%时,初晶硅由未变质前的97μm减小到65μm,减小了33%;当将熔体温度处理工艺与磷变质处理相结合时,此时Al-20%Si合金中的初晶硅尺寸减小至36μm,减小了62%,且钝化现象显著,弥散分布于α-Al基体上,共晶硅也由未变质前的长针状变为短纤维状和点状。     

稀土Er对Al-Si-Cu钎料显微组织与性能的影响

为了研究微量稀土元素Er对Al-7Si-20Cu钎料合金性能的影响,进行了不同wEr对Al-7Si-20Cu合金熔化温度、润湿性能及力学性能的试验研究.结果表明,添加微量Er对Al-Si-Cu钎料合金的熔化温度无显著影响,但显著提高Al-Si-Cu钎料合金对被焊基体铝合金(LF21)的润湿能力,尤其是当wEr为0.05%~0.1%时最为显著.显微组织分析表明,随着wEr的增加,钎料显微组织细化,特别是针状共晶Si的长度逐渐减小.     

Microstructure and mechanical propertiesof spray-deposited Al-Si-Fe-Cu-Mg alloy containing Mn

Al-20Si-5Fe-3Cu-1Mg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray deposited hypereutectic Al-Si alloy were studied using optical microscopy, scanning electron microscopy, X-ray diffraction, TEM (Transmission Electron Microscope) and HREM (High-resolution Electron Microscope), DSC (Differential Scanning Calorimetry), microhardness measurement, and tensile tests. The effects of Mn on the microstructural evolution of the high-silicon aluminum alloy after extrusion and heat treatment have been examined. The results show that two kinds of phases, i. e. S (Al2CuMg) and σ(Al5Cu6,Mg2), precipitated from matrix and improved the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). The tensile test results indicate that the spray-deposited Al-20Si-5Fe-3Cu-1Mg alloy has better strength than the powder metallurgy processed Al-20Si-3Cu-1Mg alloy at elevated temperature.     

Effect of P/M value on the preforms and microstructures of spray formed 70Si30Al alloy

A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.     

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.     

Pressureless infiltration of Si3N4 preforms with an Al-2wt%Mg alloy

The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms, The growth of the composite with useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope. During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AIN. The silicon produced during the growth consumed in the formation of MgSiAIO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms, First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase （AlON）, The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.     

Influence of rare earth (Ce and La) addition on the performance of Al-3.0 wt%Mg alloy

The influences of rare earth elements (cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.