电场激活燃烧合成( TiB2)PNi/Ni3Al/ Ni功能梯度材料

采用电场激活压力辅助合成技术(FAPAS)制备了(TiB₂)_PNi/(TiB₂)_PNi₃Al/Ni₃Al/Ni梯度材料,主要研究电场激活燃烧合成过程中电场对材料合成及层界面扩散连接的作用。分析了梯度材料各层的界面微观组织及相组成和材料的硬度分布。结果表明,采用FAPAS 技术结合机械合金化工艺制备的(TiB₂)_PNi/(TiB₂)_PNi₃Al/Ni₃Al/Ni 功能梯度材料具有快速、简便和组织均匀密实的特点。梯度材料的陶瓷复合层、Ni₃Al层和Ni板的界面区产生成分的互扩散,形成了良好的冶金结合。从Ni板到陶瓷复合层的硬度呈梯度分布。     

Cr镀层对立方氮化硼(cBN)－玻化陶瓷复合材料界面成分、结构的作用

本文用DTA、XRD、SEM、EPMA等研究了Cr镀层与cBN晶体在600～1000℃范围的界面反应过程,以及界面成分结构特征,讨论了Cr镀层在烧结时与SiO₂-Na₂O-B₂O₃玻化结合剂的的作用。结果表明,Cr镀层与cBN晶体在600℃以上发生界面反应形成CrN,800℃以上开始形成CrB₂,这些在cBN晶体上外延生长的难熔化合物使Cr镀层与cBN牢固结合并阻止了结合剂中碱性组分对cBN的侵蚀,实现了cBN与玻化结合剂间的化学键结合。     

碳纳米管化学镀镍及镍层形貌控制研究

利用胶体钯溶液对碳纳米管(CNTs)进行活化处理,再采用化学镀的方法在碳纳米管表面沉积金属镍镀层,得到镀镍碳纳米管(Ni/CNTs)。通过场发射扫描电子显微镜(FESEM)、能量色散谱(EDS)、X射线衍射(XRD)和分光光度法对Ni/CNTs和镀液进行表征,分析了镍镀层形成的热力学条件与过程。结果表明:CNTs化学镀镍层为非晶态；CNTs浓度及反应温度对Ni²⁺沉积速率无明显影响；NaOH和NaH₂PO₂浓度与Ni²⁺沉积速率呈线性关系；镍镀层生长符合球形融合模型,通过改变CNTs浓度,可对镀层形貌进行有效调控。     

碳化硅与氧化铝界面化学稳定性研究

借助最新最权威基本的热力学数据,按化学平衡理论,分析SiC和Al₂O₃之间可能发生的化学反应,定量计算SiC中不同C活度、不同固相产物活度,不同温度下SiC和Al₂O₃间诸反应各气相产物分压和分压总和,精确分析SiC和Al₂O₃界面的热力学稳定性,提供一个大气压惰性气体环境SiC和Al₂O₃界面的热力学失稳判据,为SiC材料研究者提供可靠的参考资料。     

原始SiC颗粒表面及SiCP/Al复合材料界面化学状态的研究

本文采用X射线光电子谱(XPS)和俄歇能谱技术(AES)对原始SiC颗粒表面和粉末冶金法制备的SiC_P/Al复合材料界面的化学状态进行了研究.结果表明:原始SiC颗粒表面主要存在SiC、SiO₂、游离C、吸附氧、Fe₂O₃等;SiC_P/Al复合材料界面存在Mg偏聚和氧元素.由热力学分析可知,Mg元素能够向界面偏聚,并可能与界面处的氧反应生成MgO.     

Cr13 Ni5Si2 /γ-Ni 三元金属硅化物高温耐磨复合材料

采用激光熔化/ 连续沉积工艺制备出以Cr₁₃Ni₅Si₂ 三元金属硅化物为初生相、以γ2Ni 基固溶体为连续增韧相(基体) 的三元金属硅化物耐磨复合材料(Cr₁₃Ni₅Si₂ /γ) 。在高温滑动磨损条件下测试了Cr₁₃Ni₅Si₂ /γ复合材料的耐磨性能随温度的变化规律, 并讨论了其磨损机理。结果表明, 由于Cr₁₃Ni₅Si₂ 三元金属硅化物具有原子结合力强和硬度2温度关系反常等特点, 且Cr₁₃Ni₅Si₂ /γ复合材料具有优良的强韧性配合, 以及Cr₁₃Ni₅Si₂ /γ复合材料在高温磨损过程中磨损表面能够形成转移覆盖层, Cr₁₃Ni₅Si₂ /γ材料在高温滑动磨损条件下具有非常优异的耐磨性能, 较低的磨损温度敏感性和反常的磨损2温度关系。韧性基体γ-Ni 的加入使Cr₁₃Ni₅Si₂ 三元金属硅化物在600 ℃高温下滑动耐磨性能提高了3 倍。     

激光熔敷Cr3Si/Cr2Ni3Si复合材料涂层组织与耐磨性研究

以Cr-Si-Ni合金粉末为原料、利用激光熔敷技术在A3低碳钢表面上制得了以金属硅化物Cr₃Si为增强相,以Cr₂Ni₃Si复杂金属硅化物为基体的快速凝固Cr₃Si/Cr₂Ni₃Si复合材料冶金涂层,分析了该涂层的显微组织,并分别在干滑动磨损及二体磨料磨损条件下测试了该涂层的耐磨性能。研究结果表明,由于激光熔敷Cr₃Si/Cr₂Ni₃Si快速凝固复合材料涂层组织细小、均匀,在滑动磨损过程中不易与对偶件粘着、在磨料磨损过程中具有很高的抗切削抗剥落能力,因而在干滑动磨损及二体磨料磨损条件下涂层均具有优良的耐磨性能。     

金刚石表面的Ti、Mo、W镀层及界面反应对抗氧化性能的影响

为了提高工业金刚石的抗氧化能力,本文用XRD、SEM、DTA和TGA等方法研究了Ti、Mo、W镀层与金刚石界面反应过程、结构特征及对金刚石抗氧化性能的影响.结果表明:Ti在高于600℃、Mo在高于650℃、W在高于650℃与金刚石界面发生固相反应,通过反应扩散过程在金刚石表面外延生长成相应的TiC、MoC+Mo₂C及WC+W₂C碳化物层.该致密连续的碳化物层具有较高的抗氧化能力,延缓了金刚石表面的氧化.镀Ti、Mo、W金刚石在空气中的氧化温度达958℃、871℃和880℃.Ti、Mo、W镀层经真空碳化处理后,抗氧化温度分别达1024℃、977℃和986℃.而未镀金刚石在780℃以上即开始氧化.     

Sn-2Ag-2.5Zn低银含量合金焊料界面反应

共晶Sn-Ag-Cu无铅焊料由于成本和可靠性问题导致应用受到限制,将Sn-2Ag-2.5Zn低银含量合金焊料与不同基板焊接,研究焊接后界面反应以及随后不同时效处理条件下的组织形貌变化及可靠性。Sn-2Ag-2.5Zn焊料由直接熔炼法制成焊球,将焊球置于焊接强度测试仪中与基板加热焊接,随后将焊点置于加热炉中进行时效处理。结果表明:焊料与裸Cu基板焊接,时效处理后在界面处形成Cu₅Zn₈和Ag₃Sn致密双层IMC结构,双层结构相互阻隔,限制铜锡IMC的发展。焊料与电镀有Ni阻挡层Cu基板焊接,焊接界面形成薄层Ni₃Sn₄金属化合物,时效1 000 h后Ni₃Sn₄的厚度约为1 μm,Ni阻挡层的厚度保持在2~3 μm, Ni阻挡层的阻挡效果稳定。Sn-2Ag-2.5Zn焊料在长时效处理中损耗性能优良,耐热时效处理性好,焊料连接的质量较好,界面可靠性较高,对环境污染少。Sn-2Ag-2.5Zn焊料中低银含量使得成本大幅下降,不容易形成粗大的金属间化合物Ag₃Sn,性能有所改善,是一种非常有应用前途的合金焊料。     

硅酸铝短纤维增强AZ91D复合材料的界面微观结构及力学性能

以晶化的硅酸铝短纤维（Al₂O₃-SiO₂ ）_sf为增强体、用磷酸铝为预制体粘结剂,通过挤压浸渗工艺制备了（Al₂O₃-SiO₂ ）_sf /AZ91D镁基复合材料。通过光学显微镜、TEM和HREM分析研究了复合材料的界面微观结构和界面反应产物。结果表明：用挤压浸渗法制备的硅酸铝短纤维增强AZ91D镁基复合材料的界面厚度约为100 nm,界面上除有一定数量的MgO颗粒和少量的MgAl₂O₄和Mg₂Si颗粒外, 还有少量的MgP₄等反应产物存在;硅酸铝增强纤维与镁合金基体之间形成了较强界面结合,界面微观结构比较理想。力学性能测试表明,与AZ91D基体合金相比,复合材料的室温抗拉强度提高了约18%,弹性模量提高了约58%。     

无压浸渗法制备氧化态SiC颗粒增强铝基复合材料

研究了SiC颗粒在1000~1200℃的氧化行为, 其氧化增重率与保温时间符合抛物线规律, 氧化增重受扩散过程控制, 氧化激活能为219 kJ/mol. 采用预氧化处理的SiC颗粒为增强体, 含Si、Mg的铝合金为基体, 通过无压浸渗方法制备了SiC_p/Al复合材料, 分析了复合材料的微观组织与界面形貌, 探讨了无压浸渗机理. 复合材料中颗粒分布均匀, 无偏聚现象. 材料制备过程中存在界面反应, SiC颗粒表面的氧化层与铝合金中的Mg、Al反应形成了一定数量的MgAl₂O₄. 界面反应的存在提高了润湿性, 促进了无压自发浸渗.     

SiC／Ni3Al界面固相反应区的相组成与显微结构

使用光学显微镜、扫描电子显微镜和能谱仪等对1000℃×5h加热处理的SiC／Ni3Al界面固相反应区显微结构、相组成以及反应区中元素分布等进行观察、分析和测试。研究表明,SiC／Ni3Al界面固相反应形成Ni2Si、石墨态碳沉积物和Ni5.4AlSi2。SiC／Ni3Al界面固相反应形成两层结构的反应区,其厚度大约是16μm。其中,靠近SiC侧的反应区由Ni2Si,Ni5．4AlSi2和分布在其中的颗粒状的石墨颗粒构成,而靠近Ni3Al侧的反应区则由Ni2Si和Ni5．4AlSi2构成。     

Ni-P-(Ni/SiC)P镀层及其工艺条件的研究

为解决Ni-P-(SiC)P镀层中基体的金属键与增强体的共价键间相容性差,增强体颗粒易脱落,镀层性能降低等问题.采用简单的化学镀方法实现了(SiC)P表面修饰、改性,得到了涂覆型改性(Ni/SiC)P,以(Ni/SiC)P为第二相粒子制备了Ni-P-(Ni/SiC)P化学复合镀层,并初步分析了复合镀机理.实验结果表明:温度、pH值、搅拌速率及(Ni/SiC)P加入量对Ni-P-(Ni/SiC)P镀层的沉积速率及沉积量有较大的影响,本实验条件下的最佳温度为82~86℃;最佳pH值为4.2~4.6;最佳搅拌速率为200 r/mim;最佳粒子加入量10 g/L.SEM、EDS分析显示Ni-P-(Ni/SiC)P镀层均匀、致密,Ni、P、Si沉积量大,耐磨性实验证明Ni-P-(Ni/SiC)P化学复合镀层硬度、耐磨性优于常见的Ni-P、Ni-P-(SiC)P镀层.经表面修饰、改性后得到的(Ni/SiC)P可以进一步提高Ni-P-(SiC)P镀层的使用性能.     

Brazing of SiC to a wrought nickel-based superalloy using CoFeNi(Si, B)CrTi filler metal

Newly-developed CoFeNi(Si, B)CrTi brazing filler metal was used for joining of SiC to a wrought nickel-based superalloy (GH3044). The brazing alloy was fabricated into brazing foils by a rapid solidifying technique, and the brazing temperature was fixed at 1150 °C. The SiC/GH3044 joints using single interlayer Ni or triple interlayers of Ni/W/Ni showed very low strength, and this was because the Ni severely interfered with the normal reactions between the SiC and the brazing alloy. When using triple interlayers of Kovar/W/Ni for the SiC/GH3044 joining, the joint strength was remarkably elevated to 62.5-64.6 MPa. Kovar has a low coefficient of thermal expansion. Moreover, when Kovar was used as an interlayer neighboured to the brazed SiC, it basically ensured the normal interfacial reactions between the brazed SiC and the used brazing alloy. These two factors should account for the improvement of the joint strength.     

Tunable strength of SiCf/β-Yb2Si2O7 interface for different requirements in SiCf/SiC CMC:Inspiration from model composite investigation

Model composites consisting of Si C fiber embedded inβ-Yb₂Si₂O₇ matrix were processed by Spark Plasma Sintering method and the feasibility of tunable Si Cf/Yb₂Si₂O₇ interface in Si C-based CMCs were estimated.Weak and strengthened Si Cf/Yb₂Si₂O₇ interfaces were achieved by adjusting sintering temperatures.The indentation crack test and fiber push out experiments clearly demonstrated the different debonding mechanisms in the samples.Weak interfaces sintered at 1200 and 1250℃exhibited crack deflection at interface in indentation test.Their low debond energy at the interface,which were comparable to those of Py C or BN,satisfied the well-recognized interfacial debond and crack deflection criteria for CMCs.The interface was strengthened by atomic bonding in model composite sintered at 1450℃,leading to crack penetrating into Si C fiber and high debond energy.The strong interface may be promising in Si Cf/Si C CMC to withstand higher combustion temperature,because Yb₂Si₂O₇ will provide plastic deformation capacity,which would serve as weak interphase for crack deflection and energy dissipation.Therefore,it is possible to design the capability of Si C_f/RE₂Si₂O₇ interface for different requirements by adjusting interfacial strength or debond energy to reach optimal mechanical fuse mechanism in SiC_f/SiC CMC.     

镀液中SiC含量和粒径对Ni-P-SiC复合化学镀层性能的影响

采用化学镀方法制备了Ni P SiC复合镀层 ,系统研究了镀液中SiC含量和粒径对镀层结构及显微硬度的影响。结果表明 ,镀层中SiC析出量随镀液中SiC含量的增加而增加 ,在SiC含量一定的情况下 ,当SiC粒径为 7.0 μm时 ,析出量最大 ;镀液中SiC的含量和粒度对原始镀层的硬度影响不大 ,但对 4 0 0℃热处理后的镀层硬度有显著影响     

Wettability and interfacial reaction in SiC/Ni plus Ti system

Wettability and interfacial reactions in both SiC ceramic/pure Ni system and SiC ceramic/Ni plus Ti system were studied. The contact angle was determined by high temperature photography. The microstructure and composition of the interfacial region were analyzed. Under the applied experimental conditions, the contact angle of SiC/pure Ni system at 1350°C in vacuum is about 86°. The contact angle slightly decreases with the prolonging of time of the test at 1350°C. The interfacial reactions take place during the test. The reactions facilitate the wetting. The wettability of the system is improved by adding active element titanium into the metallic phase. The contact angle decreases with the increasing of content of the additive within the tested range. Moreover, this effect becomes more remarkable with the prolonging of reaction time at high temperatures. This can be explained by the fact that titanium accumulates at the wetting interface and facilitates the interfacial reactions, resulting in an increase of the driving force of wetting.     

Interfacial reactions in aluminum/SiC fibre composite electric power cable using low oxygen SiC fibre reinforcement

We have evaluated the interfacial reactions of SiC fibre reinforced Al electrical power cable using low oxygen SiC fibre (Si : 62.4, C : 37.1, 0 : 0.5 mass%), and determined the relationship between the tensile strength and the amount of reaction products at the interface. The following are occurring at the SiC/Al interface: i) diffusion of Al atoms into the SiC fibre, ii) formation of needle–shape Al₄C₃ compounds, and iii) formation of Al₉Si compounds. Formation of Al₄C₃ and Al₉Si compounds at the interface causes the strength of SiC/Al composite electric power cable to deteriorate.     

Analysis of tensile strength and microstructure of Ni–SiC composites prepared by electroforming

Ni–SiC metal matrix composites with two kinds of SiC content were prepared by electroforming in a nickel sulphamate bath. Tensile strength and microstructure of the composites before and after heat treatment were investigated. The maximum of tensile strength was obtained after heat treatment at 300 °C × 24 h. The values were 641 N/mm² and 701 N/mm² respectively. The complete reaction between nickel and SiC particles can produce shrinkage pores in the interface. The volume of shrinkage pores was equal to 8% of the volume of SiC particles in the composites. The interfacial reaction products were composed of Ni₃Si and a little amount of Ni₃₁Si₁₂ after heat treatment at 600 °C × 24 h. The fracture evolution went though microcracks initiation, growth and coalescence. Cracking of the matrix, debonding of Ni–SiC interfaces and cracking of particles were three types of cracking modes for Ni–SiC composites.     

常规铸造工艺条件下SiCp/Al-Si复合材料中的界面反应

采用搅拌复合法制备了10%SiC／Al—5Si—Mg，10%SiC／Al—7Si—Mg(体积分数)复合材料，研究了在常规铸造工艺条件下重熔后复合材料中的界面反应。通过透射电镜和能谱分析可知，SiC界面基本上都是单一的SiC／Al及SiC／Si界面，部分界面上有MgAl2O4颗粒相形成，由于基体合金中Si的存在，生成Al2C3的有害界面化学反应得到了抑制。对不同文献中抑制Al4C3产生所需临界Si含量实验测定结果的差异进行了分析。