二相TiAl基金属间化合物层片结构中的位错组态

二相ＴｉＡｌ基金属间化合物层片结构中的位错组态孟祥康，洪建明，刘毅，赵晓宁，刘治国（南京大学固体微结构物理实验室南京大学现代分析中心，上海交通大学材料科学系）ＴｉＡＬ基金属间化合物具有优良的高温性能和高比强度，被认为是理想的航空航天结构材料，只是其低...     

金属间化合物TiAl（Mn）中γ／α2相界面上的缺陷研究

略富Ti的TiAl金属间化合物具有优良的机械性能和较小比重等优点,其塑性差也可以通过加入Mn等合金元素以及适当地控制层状组织而得到改善。这说明γ和α_2相之间的相界面对于改进其机械性能起着重要作用。在这些层状结构中,γ相和α相总是具有固定的取向关系{111}_γ∥(0001)α_2和〈112〉_γ∥〈1120〉α_2。由于他们的点阵常数存在着一定差别,在其界面上常常形成一系列台阶位错和应力集中。这篇报告将对这些界面上的缺陷的特点及分布进行研究,并试图用O点阵理论解释其成因。实验用合金的重量百分比为Ti-34%Al-2%Mn。其热处理制度为:1250℃保温2小时,空冷至室温;再900℃保温4小时,空冷至室温。     

金属间化合物超塑性变形中的小角度界面位错

利用透射电子显微镜弱束成像技术研究了金属间化合物ＦｅＡｌ超塑性变形后的小角度晶界位错特征，发现一篑上型位借构成的小角度晶界，分析了其形成机理，讨论了其对材料力学性能的影响。     

TiAl基合金中的相变诱发位错网

双相ＴｉＡｌ合金的层状组织在α+γ两相区退火时将发生组织退化[1,2 ] ,即ｙ层片合并以及形成不连续的α2 层片。不同变体的相邻ｙ层片合并后 ,在局部区域内将残留位错网[3] 。另一方面 ,从相图上看 ,在α2 +γ两相区内 ,随温度升高 ,与γ相平衡的α2 相将有所增加。但层状组织的形成也可能在较高温度的α +γ两相区开始 ,在这种情况下 ,较多的α层片在α2 +γ两相区中的低温区优先转变为α2 层片 ,使层状组织中α2 相的体积分数超过其平衡体积分数 ,当加热至α2 +γ两相区中高温度区时 ,部分α2 层片则可能发生分解。为进一步理解ＴｉＡｌ…     

高温变形FeAl金属间化合物中的位错蜷线

高温变形ＦｅＡＬ金属间化合物中的位错蜷线洪建明，赵晓宁，刘毅，郦定强，林栋梁，陈世朴（南京大学现代分析中心，南京２１０００８）（上海交通大学材料科学系）具有Ｂ＿２结构的金属间化合物ＦｅＡｌ，由于具有良好的抗氧化性能、高温性能、比铁基和镍基合金较低的密...     

TiAl金属间化合物合金的激光气体合金化表面改性研究

对TiAl金属间化合物合金进行激光气体合金化表面改性.在激光表面改性层中成功地制得了以高硬度氮化钛为增强相的新型快速凝固“原位”耐磨复合材料.激光表面改性层厚度及显微组织与显微硬度均受激光处理工艺参数的控制.初步试验结果表明,激光气体合金化是一种很有前途的提高TiAl金属间化合物合金耐磨性的表面改性新技术.     

TiAl金属间化合物合金碳元素脉冲激光表面合金化显微组织及TiC快速凝固生长形态研究

利用脉冲激光,以C作为合金元素,TiAl金属问化合物进行激光表面合金化,制得了以TiC为增强相、以TiAl为基体的快速凝固复合材料涂层、研究了快速凝固条件下增强相TiC的生长形态及其微观生长机制。     

γ-TiAl金属间化合物合金激光熔敷高温自润滑耐磨复合材料涂层

以 Ｎｉ８ＯＣｒ２０、Ｃｒ_３Ｃ_２、Ａｒ、ＣａＦ_２／ＢａＦ_２四元混合粉末为原材料,利用激光熔敷技术在ｒ－ＴｉＡｌ金属间化合物合金Ｔｉ－４８Ａｌ－２Ｃｒ－２Ｎｂ表面上制得了以ｒ一ＮｉＣｒ为基体、以初生Ｍ_７Ｃ_３及Ｍ_（２３）Ｃ_６为耐磨相、以弥散分布颗粒Ａｇ、ＣａＦ_２或ＣａＡｇＦ_４为自润滑相的高温自润滑耐磨复合材料涂层,涂层显微硬度大大提高且与基体呈冶金结合。     

利用电子显微术研究金属间化合物中的一些问题

金属间化合物具有有序固溶体的特征,即具有简单的原子理想配比关系。对于金属相一般情况下,这些简单比例关系与价的比例关系不符合,但却必须与在晶体点阵中,原子呈有序排列时的各种固定位置种类的比值相符合。由于它的结构特点,使金属间化合物具有某些特殊性能和用途。本工作介绍我们如何利用分析电子显微术来研究某些金属间化合物中的一些问题: 1.界面的有序度及成份测定     

62Sn－36Pb－2Ag焊点的可靠性及热疲劳位错亚结构的演化分析

采用热疲劳试验分析了表面封装焊点的可靠性。讨论了不同的元器件及基片镀层工艺对焊点可靠性的影响，初步探讨了热疲劳过程中位错亚结构的变化及焊点的失效机理。结果表明：金属间化合物对焊点失效有重要影响．镀Ａｕ焊点热疲劳裂纹萌生于ＡｕＳｎ４金属间化合物并在其中扩展，镀Ｎｉ／Ａｕ焊点热疲劳过程中位错在ＡｕＳｎ４粒子处塞积，引起ＡｕＳｎ４／β－Ｓｎ界面应力集中，导致热疲劳裂纹沿ＡｕＳｎ４／β－Ｓｎ界面萌生，萌生后的裂纹在β－Ｓｎ相中扩展，ＴＥＭ观察也证明β－Ｓｎ相中位错密度较高。     

Failure Mechanisms and Crack Propagation Paths in Thermally Aged Pb-Free Solder Interconnects

Studies were conducted on Pb-free solder interconnects after aging for up to 1,000 h at temperatures of up to 150°C and submitting to drop testing. Cracks were shown to propagate along interphase boundaries (bulk solder/Cu₆Sn₅, Cu₆Sn₅/Cu₃Sn, Cu₃Sn/Cu, and bulk solder/Ag₃Sn) and along the bulk solder. Intergranular propagation in the solder was rarely observed, although cross sectioning showed evidence of that particular path. There is a transition in preferred crack propagation with aging time and temperature, from the intermetallic layer to the bulk solder. Sulfur was found in the fracture surfaces and may be a weakening agent in these solders.     

形变铜中位错组态的电镜分析

本文用ＴＥＭ衍射成像技术观察在室温下形变铜中位错胞结构的产生与发展，测定了胞壁厚及位错环尺寸等应变的变化规律，并探讨了胞尺寸与位错密度，流变应力之间定量关系的存在。     

Investigation of Dissolution Behavior of Metallic Substrates and Intermetallic Compound in Molten Lead-free Solders

This study investigates the dissolution behavior of the metallic substrates Cu and Ag and the intermetallic compound (IMC)-Ag₃Sn in molten Sn, Sn-3.0Ag-0.5Cu, Sn-58Bi and Sn-9Zn (in wt.%) at 300, 270 and 240°C. The dissolution rates of both Cu and Ag in molten solder follow the order Sn > Sn-3.0Ag-0.5Cu >Sn-58Bi > Sn-9Zn. Planar Cu₃Sn and scalloped Cu₆Sn₅ phases in Cu/solders and the scalloped Ag₃Sn phase in Ag/solders are observed at the metallic substrate/solder interface. The dissolution mechanism is controlled by grain boundary diffusion. The planar Cu₅Zn₈ layer formed in the Sn-9Zn/Cu systems. AgZn₃, Ag5Zn₈ and AgZn phases are found in the Sn-9Zn/Ag system and the dissolution mechanism is controlled by lattice diffusion. Massive Ag₃Sn phases dissolved into the solders and formed during solidification processes in the Ag₃Sn/Sn or Sn-3.0Ag-0.5Cu systems. AgZn₃ and Ag₅Zn₈ phases are formed at the Sn-9Zn/Ag₃Sn interface. Zn atoms diffuse through Ag-Zn IMCs to form (Ag, Zn)Sn₄ and Sn-rich regions between Ag₅Zn₈ and Ag₃Sn.     

Direct Growth of Uniform Bimetallic Core-Shell or Intermetallic Nanoparticles on Carbon via a Surface-Confinement Strategy for Electrochemical Hydrogen Evolution Reaction

Due to the surface inhomogeneity of the solid supports, direct growth of uniform bimetallic nanoparticles (NPs) with controllable structure and size thereon is particularly challenging. Herein, a surface-confinement strategy is reported to directly prepare ultrafine bimetallic Pt M NPs (MFe, Cu, and Co) with structure of core-shell or intermetallic compounds on an N functionalized carbon support (NC). It is found that the N species of NC support can atomically disperse metal cations of precursors, which largely renders uniform nucleation and growth of bimetallic NPs and fine structure modulation of them. In another regard, metal transfer is confined to a narrow region on NC via N-mediation, hence greatly favoring localized particle growth and formation of ultrafine bimetallic NPs. Remarkably, the ultrafine 3.1 ± 0.7 nm intermetallic Pt₃Fe NPs on NC displayed excellent catalytic activity and durability toward electrochemical hydrogen evolution reaction.     

Nonprecious Intermetallic Al7Cu4Ni Nanocrystals Seamlessly Integrated in Freestanding Bimodal Nanoporous Copper for Efficient Hydrogen Evolution Catalysis

Tremendous demands for renewable hydrogen generated from water splitting have stimulated intensive research on developing earth‐abundant, non‐noble, and versatile metal catalysts toward the hydrogen evolution reactions (HER). Here, self‐supported Cu‐Ni‐Al hybrid electrodes that are composed of electroactive Al₇Cu₄Ni@Cu₄Ni core/shell nanocrystals seamlessly integrated in self‐supported 3D bimodal nanoporous Cu skeleton (Bi‐NP Cu/Al₇Cu₄Ni@Cu₄Ni) as robust HER electrocatalysts in alkaline electrolyte are reported. As a result of the proper architecture, in which the Bi‐NP Cu skeleton not only facilitates both electron and electrolyte transports but also provides high specific surface areas to fully use high electrocatalytic activity of Al₇Cu₄Ni@Cu₄Ni core/shell nanocrystals, the Bi‐NP Cu/Al₇Cu₄Ni@Cu₄Ni hybrid catalysts exhibit a low onset overpotential of 60 mV and a small Tafel slope of 110 mV dec^?1, enabling the catalytic current density of 10 mA cm^?2 at a low overpotential of 139 mV. The highly stable electrochemical performance makes them promising candidates as cathode catalysts in alkaline‐based devices.     

Intermetallic reactions in a Sn-20In-2.8Ag solder ball-grid-array package with Au/Ni/Cu pads

The intermetallic compounds formed during the reflow and aging of Sn-20In-2.8Ag ball-grid-array (BGA) packages are investigated. After reflow, a large number of cubic-shaped AuIn₂ intermetallics accompanied by Ag₂In precipitates appear in the solder matrix, while a Ni(Sn_0.72Ni_0.28)₂ intermetallic layer is formed at the solder/pad interface. With further aging at 100°C, many voids can be observed in the solder matrix and at the solder/pad interface. The continuous distribution of voids at the interface of specimens after prolonged aging at 100°C causes their bonding strength to decrease from 5.03 N (as reflowed) to about 3.50 N. Aging at 150°C induces many column-shaped (Cu_0.74Ni_0.26)₆(Sn_0.92In_0.08)₅ intermetallic compounds to grow rapidly and expand from the solder/pad interface into the solder matrix. The high microhardness of these intermetallic columns causes the bonding strength of the Sn-20In-2.8Ag BGA solder joints to increase to 5.68 N after aging at 150°C for 500 h.     

Intermetallic phase detection in lead-free solders using synchrotron x-ray diffraction

The high-intensity, high-resolution x-ray source at the European Synchrotron Radiation Facility (ESRF) has been used in x-ray diffraction (XRD) experiments to detect intermetallic compounds (IMCs) in lead-free solder bumps. The IMCs found in 95.5Sn3.8Ag0.7Cu solder bumps on Cu pads with electroplated-nickel immersion-gold (ENIG) surface finish are consistent with results based on traditional destructive methods. Moreover, after positive identification of the IMCs from the diffraction data, spatial distribution plots over the entire bump were obtained. These spatial distributions for selected intermetallic phases display the layer thickness and confirm the locations of the IMCs. For isothermally aged solder samples, results have shown that much thicker layers of IMCs have grown from the pad interface into the bulk of the solder. Additionally, the XRD technique has also been used in a temperature-resolved mode to observe the formation of IMCs, in situ, during the solidification of the solder joint. The results demonstrate that the XRD technique is very attractive as it allows for nondestructive investigations to be performed on expensive state-of-the-art electronic components, thereby allowing new, lead-free materials to be fully characterized.     

Joint Strength and Microstructure for Sn-Ag-(Cu) Soldering on an Electroless Ni-Au Surface Finish by Using a Flux Containing a Cu Compound

The effect of a flux containing Cu(II) stearate (barrier flux) on the strength of soldered joints between an electroless Ni-Au surface finish and two Pb-free soldering systems, Sn-3Ag-0.5Cu and Sn-3.5Ag (wt.%), was examined. Pull and shock tests showed that barrier flux gave a higher joint strength for both solder compositions than did a flux containing no Cu compounds. Interface analysis revealed that a thin P-rich layer and refined Cu-Ni-Sn intermetallic compounds were formed at the joint interface when barrier flux was used. It is assumed that the supply of Cu from barrier flux suppresses diffusion of Ni into the solder.     

Intermetallic Reactions in Sn-0.4Co-0.7Cu Solder BGA Packages with an ENIG Surface Finish

As-cast Sn-0.4Co-0.7Cu solder contains both (Cu_0.98Co_0.02)₆Sn₅ and (Co_0.85Cu_0.15) Sn₃ intermetallic phases in the matrix. After reflowing, the Au thin film in the electroless Ni/immersion Au (ENIG) surface-finished Sn-0.4Co-0.7Cu solder ball grid array (BGA) packages dissolved rapidly into the solder matrix to form AuSn₄ intermetallics, and a thin layer of (Cu_0.57Ni_0.35Au_0.08)₆Sn₅ intermetallic compound appeared at the solder/pad interface, growing very slowly during aging at 100°C. Increasing the aging temperature to 150°C caused the formation of a new intermetallic layer, (Ni_0.79Cu_0.21)₃Sn₄, at the (Cu_0.57Ni_0.35Au_0.08)₆Sn₅/Ni interface. The reflowed Sn-0.4Co-0.7Cu BGA packages have a ball shear strength of 6.8 N, which decreases to about 5.7 N and 5.5 N after aging at 100°C and 150°C, respectively. The reflowed and aged solder joints fractured across the solder balls with ductile characteristics in ball shear tests.     

Intermetallic reactions in Sn-3.5Ag solder ball grid array packages with Ag/Cu and Au/Ni/Cu pads

During the reflow process of Sn-3.5Ag solder ball grid array (BGA) packages with Ag/Cu and Au/Ni/Cu pads, Ag and Au thin films dissolve rapidly into the liquid solder, and the Cu and Ni layers react with the Sn-3.5Ag solder to form Cu₆Sn₅ and Ni₃Sn₄ intermetallic compounds at the solder/pad interfaces, respectively. The Cu₆Sn₅ intermetallic compounds also appear as clusters in the solder matrix of Ag surface-finished packages accompanied by Ag₃Sn dispersions. In the solder matrix of Au/Ni surface-finished specimens, Ag₃Sn and AuSn₄ intermetallics can be observed, and their coarsening coincides progressively with the aging process. The interfacial Cu₆Sn₅ and Ni₃Sn₄ intermetallic layers grow by a diffusion-controlled mechanism after aging at 100 and 150°C. Ball shear strengths of the reflowed Sn-3.5Ag packages with both surface finishes are similar, displaying the same degradation tendencies as a result of the aging effect.