Fabrication of Short Carbon Fiber Reinforced AZ91D Alloy by Infiltration-Extrusion Integrated Technique

Short carbon fiber reinforced AZ91D alloy (Csf/AZ91D) was fabricated by the infiltration-extrusion method. The short carbon fiber preform was infiltrated with melted AZ91D alloy under the assistant of gas pressure. The extrusion processing was applied following the infiltration processing directly. The tensile property and microstructure of the Csf/AZ91D and that of the die-casting and extruded AZ91D alloy was compared. The results show that the short carbon fiber reinforced AZ91D alloy present excellent te...     

Wear Behavior of the Uniformly Dispersed Carbon Nanotube Reinforced 6061Al Composite Fabricated by Milling Combined with Powder Metallurgy

The uniformly dispersed carbon nanotubes(CNTs) reinforced 6061Al composites(CNT/6061Al) with diff erent CNT concentrations were fabricated by powder metallurgy technology. It was found that the friction coe ffi cient as well as wear rate decreased fi rst and then increased as the CNT concentration increasing under 15 N as well as 30 N, and the minimum wear rate was achieved at the CNT concentration of 2 wt%. Adhesive wear and abrasive wear were the dominated wear mechanisms for the 1–2 wt% CNT/6...     

挤压态AZ61镁合金磨损性能研究

主要研究了挤压态AZ61镁合金在不同载荷和滑动摩擦速度条件下的磨损性能。采用SEM对磨损面进行显微组织观察与分析,讨论了不同载荷下材料的主要磨损形式。结果表明,磨损质量损失随着滑动摩擦速度和载荷的增加而增加。挤压态AZ61镁合金的磨损机制主要分为轻微磨损和严重磨损。轻微磨损主要是擦伤磨损、氧化磨损与剥层磨损,在磨损面上形成的擦痕与裂纹,其磨损程度较轻,磨损面积小;当载荷增加到100N和120N时,塑性变形和熔化在磨损面形成的磨痕较深且磨损面积大,表现为严重磨损。     

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     

三维连续镍-铝(骨架)增强铝基复合材料的磨损行为

采用真空吸铸和真空热处理技术制备了三维连续镍-铝(骨架)增强铝基复合材料,研究了其在干摩擦条件下的磨损行为.结果表明,复合材料的耐磨性能远优于基体合金.主要是由于硬的Ni2 Al3金属间化合物(骨架)裸露在磨损表面,成为微凸体,起承载作用,抑制或延迟了基体从轻微磨损向严重磨损的转变时间.同时将载荷分散至各个方向,抑制了磨损面基体合金因塑性变形产生的流失.基体合金的磨损机制为严重粘着磨损,复合材料的磨损为以磨粒磨损为主和轻微的粘着磨损.     

纳米碳管增强镁基复合材料应力传递有限元分析

结合有限元的分析方法,建立了一个简化模型来模拟纳米碳管增强镁基复合材料在拉伸试验过程中的变形,研究了基体、增强体的应变和应力分布,以及界面对复合材料力学行为的影响,探讨了纳米碳管增强体与基体间的应力传递机制和断裂机理。模拟结果表明,纳米碳管整体上受力比较均匀,在轴向上的界面处出现应力集中;基体与纳米碳管在两端面的接触部位出现明显的应力集中,应力分布呈火焰状,中心大,逐渐向外围减小,在基体的其余部位应力大小则是相对均匀的,这说明复合材料的破坏是从界面处开始的,其破坏机制是界面脱开。     

纳米碳管增强镁基材料的复合工艺及性能研究

采用正交试验方法研究了碳纳米管加入量、复合温度、搅拌时间等工艺参数对用铸造方法制备纳米碳管增强镁基复合材料过程的影响,并探讨了这些工艺参数对复合材料力学性能和显微组织的作用.试验结果表明:碳纳米管(CNTs)能明显细化复合材料的晶粒组织,提高复合材料的抗拉强度、伸长率.在3个工艺参数中,CNTs对材料的力学性能影响最大,其含量约为1%时对力学性能最为有利;其次是加热温度,温度取低值(680 ℃)较好;搅拌时间在3 min时,其综合性能较好.影响材料拉伸强度的3个因素最优组合为A 2B 1C 3,影响伸长率的3个因素的最优组合为A 2B 1C 3.     

碳（石墨）纤维增强镁基复合材料的界面研究

采用透射电子显微技术及高分辨技术，对Ｃ／Ｍｇ复合材料界面的显微结构进行了研究，发现在纤维与基体的界面上存在着Ａｌ元素的偏聚；碳纤维的石墨化程度不同，界面形态不同，石墨化程度较低时，界面处有一层约１μｍ厚的细晶粒层存在，石墨化程度较高时，界面处平直光滑；界面处有析出物γ－Ｍｇ１７Ａｌ１２存在；近界面区存在着大量晶体缺陷，主要为位错和孪晶，并有残余应变层存在；当碳纤维表面有ＳｉＣ涂层时，在涂层与基体间     

Influence of Voltage on the Corrosion and Wear Resistance of MicroArc Oxidation Coating on Mg-8Li-2Ca Alloy

Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca_5(PO_4)_3(OH) and CaH_2P_2O_5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.     

Enhancing Wear Resistance of A356 Alloy by Adding CNFs Based on Ultrasonic Vibration Casting

A356–carbon nanofibers(CNFs) composites with different contents of CNFs were fabricated by ultrasonic vibration casting to investigate the effect of CNFs in the matrix on the mechanical properties and wear resistance. The worn surfaces were investigated using scanning electron microscopy(SEM). As the CNFs content was increased, strength,hardness and wear resistance were significantly enhanced and the coefficient of friction was extremely reduced. The nanocomposite containing 1.2 wt% of CNFs exhibited more than 109 HV in hardness and less than 0.35 in the coefficient of friction. Compared with the as-cast matrix, the wear rate of the optimal composite was less than one-third of the matrix sample and the microhardness exhibited about 47% enhancement of the matrix. Meanwhile, steadier and lower friction coefficient was also achieved by the composite. CNFs were observed to be either partially or fully crushed forming a carbon film that covered the surface and acted as a solid lubricant, enhancing the wear behavior significantly.     

7075铝合金的磨损行为及其机理探讨

在干摩擦条件下,以外加载荷和环境温度为变量,对7075铝合金的磨损行为进行研究.结果表明,7075铝合金随着载荷增加,出现从轻微磨损到严重磨损的转变,并且随温度的升高磨损转变的临界载荷大大减小.7075铝合金在常温～150℃下的磨损率明显小于200℃以上的磨损率.轻微磨损时,以磨粒磨损和氧化剥层磨损为主;严重磨损时,以热软化、粘着磨损及疲劳剥落为主.7075铝合金的磨损与其表面生成的机械混合层(MML)密切相关.当MML不被完全破坏时,其磨损率很低;一旦MML消失,就转变为严重磨损.     

原位增强Al-4.5Cu合金的高温干摩擦磨损行为研究

采用混合盐反应法制备了（TiB2＋Al3Ti）／Al-4．5Cu原位复合材料，研究了高温下载荷和温度对该复合材料同球磨铸铁对磨时干摩擦磨损行为的影响。结果表明，高温下（100—250℃）（TiB2＋Al3Ti）／Al-4．5Ca复合材料的耐磨性优于基体合金；200℃、载荷低于30N时，复合材料的磨损量增长缓慢，但随载荷增大至60N，其磨损量增长迅速；载荷为30N、试验温度超过200℃时，复合材料的磨损量大幅度上升。复合材料在于摩擦条件下较适宜在低于200℃下工作。     

炭纤维增强镁基复合材料的制备

对炭纤维进行了表面化学镀镍处理并通过扫描电镜(SEM)评价了炭纤维化镀层。利用粉末冶金热挤压方法制备了短切炭纤维增强镁合金复合材料并通过超景深金相显微镜观察了纤维在复合材料中的分布。研究了材料中炭纤维含量为0～4%时对复合材料的影响。结果表明,镀镍炭纤维在复合体中均匀分散,炭纤维质量分数为4.0%的镁预制体采用压制压力为420MPa,烧结温度为550℃,保温0.5h后在480℃用280MPa的压力进行热挤压得到的复合材料力学性能较佳。     

莫莱石短纤维增强ZL107合金复合材料的时效特性

采用宏观硬度测定及差热分析法（ＤＳＣ）研究了莫莱石短纤维增强ＺＬ１０７合金复合材料的时效特性，结果表明，复合材料中ＧＰ区的形成因增强相的加入在一定程度上被抑制，在１４０℃时效初期基体合金表现出较快的硬度增加趋势；在２０５℃时效，复合材料表现时效加速现象。随纤维加入量的增加，基体中二次Ｓｉ的析出加快。     

转速对压铸镁合金AZ91D摩擦磨损特性的影响

采用MM-200型磨损试验机研究了转速对压铸镁合金摩擦磨损性能的影响,同时对其磨损机理进行了探讨。结果表明,转速越高,压铸镁合金的磨损损失越大、摩擦因数越小。低转速时,材料的磨损机制以磨粒磨损和氧化磨损为主;高速条件下,随着磨损时间的增加,其磨损机制已转化为以剥落磨损和熔化磨损为主。T6热处理改善了高速磨损条件下镁合金材料的耐磨性能。     

短切石英纤维增强氮化物基复合材料的微观结构及强韧化机理

采用先驱体聚合物浸渍裂解法（Preceramic polymer impregnation pyrolysis，PIP）制备了短切石英纤维增强氮化物基透波复合材料（SiO2f／Si3N4-BN），对复合材料的显微结构和界面特性进行了研究，探讨了短纤维增强氮化物基复合材料的强韧化机理。力学性能测试表明复合材料弯曲强度、断裂韧性和断裂应变分别达到56．6MPa，2-3MPa．m^1/2和0．462％，介电性能优良。扫描电镜（SEM）及选区能谱（EDS）分析结果表明，氮化物基体与短切石英纤维没有发生界面反应，界面结合适中，短纤维以纤维拔出及裂纹偏转的形式使基体增强和增韧。     

硅酸铝纤维增强铝基复合材料的抗拉强度及其影响因素

研究了基体合金化,硅酸铝纤维处理方法以及不同粘结剂对硅酸铝纤维增强的铝基复合材料室温强度的影响。结果表明：基体为ＺＬ１０９铝合金的复合材料的强度高于以其它铝合金为基体的铝基复合材料;用莫来石硅酸铝纤维增强的铝基复合材料的抗位强度高于用γ型三氧化二铝纤维增强的铝基复合材料;     

高强度锌铝合金摩擦磨损特性的试验研究

采用ＭＭ２００磨损试验机，测定和对比了铸造锌铝合金（ＺＺｎＡｌ２７Ｃｕ２Ａ和ＺＺｎＡｌ２７Ｃｕ２Ｄ）和工业上常用铜合金（ＺＣｕＳｎ６Ｚｎ６Ｐｂ３，ＺＣｕＡ１１０Ｆｅ３和ＺＣｕＺｎ３３Ｍｎ２Ｐｂ２）的摩擦磨损特性。试验测定了合金在不同载荷和转速条件下的摩擦系数和磨损量及其对配对材料的磨损，结果表明，锌铝合金是一种更适于在重载低速条件下使用的减摩材料     

镁合金及镁基复合材料的高温蠕变研究进展

综述了目前镁合金及镁基复合材料的高温蠕变研究现状,介绍了镁合金的高温蠕变机理及性能提高方法,同时阐述了镁基复合材料的制备工艺及蠕变参数之间的关系、蠕变断裂机制、界面反应规律等方面的研究进展,并展望了镁基复合材料的应用前景与研究方向。     

Si对原位自生镁基复合材料摩擦磨损性能的影响

采用原位法制备Mg2Si/AM60复合材料,研究了不同质量分数的Si粉对Mg2Si/AM60复合材料摩擦磨损性能的影响。结果表明,Si质量分数增加,复合材料硬度增加,其磨损量随之减小,磨损性能得到显著加强。外加载荷增大,复合材料磨损量持续增加。与基体AM60相比,Mg2Si/AM60复合材料有效推迟微量磨损向严重磨损转变的时间。