采用Ag-Cu-Ti+Mo复合钎料钎焊Si3N4陶瓷

采用Ag-Cu-Ti+Mo复合钎料连接Si3N4陶瓷,利用SEM,TEM,Nanoindentation研究了钎料内钼颗粒含量对接头组织和力学性能的影响.结果表明,在Si3N4/钎料界面处形成了一层致密的反应层,该反应层由TiN和Ti5Si3组成.接头的中间部分由银基固溶体、铜基固溶体、钼颗粒和Ti-Cu金属间化合物组成.借助于纳米压痕技术测定了接头内Ti-Cu化合物以及钎料金属的弹性模量和硬度值.随着钎料内钼颗粒含量的提高,母材/钎料界面反应层厚度逐渐降低;钎料金属中Ti-Cu化合物数量增多;此外,银和铜基固溶体组织逐渐变得细小.当添加5%Mo时,得到最高的接头强度429.4 MPa,该强度相比合金钎料提高了114.7%.     

Nanostructure of wetting triple line in a Ag–Cu–Ti/Si3N4 reactive system

Nanometer scale structures around wetting triple lines were studied in a Ag–Cu–Ti/Si₃N₄ reactive system. Changes in the contact angle and radius of the molten metal on the substrate as a function of time were also measured in the system as macroscopic wetting behaviors. The macroscopic wetting behaviors showed two wetting stages and double layered reaction products consisting of upper Ti₅Si₃ and lower TiN layers were observed in both first and second stages. The reaction product always lay in front of the triple line defined as a triple junction of Ag–Cu–Ti alloy/Ti₅Si₃/atmosphere. At the front of the reaction product, a dominant phase changed from TiN in the first stage to Ti₅Si₃ in the second stage. It is considered that the structural change is one of the reasons why the macroscopic wetting behavior changed, and that the structural change was caused by a decrease of Ti activity as the reactive wetting progressed.     

Transient liquid phase (TLP) brazing of Mg–AZ31 and Ti–6Al–4V using Ni and Cu sandwich foils

Transient liquid phase (TLP) brazing of Mg–AZ31 alloy and Ti–6Al–4V alloy was performed using double Ni and Cu sandwich foils. Two configurations were tested; first, Mg–AZ31/Cu–Ni/Ti–6Al–4V and second, Mg–AZ31/Ni–Cu/Ti–6Al–4V. The effect of set-up configuration of the foils on microstructural developments, mechanical properties and mechanism of joint formation was examined. The results showed that different reaction layers formed inside the joint region depending on the configuration chosen. The formation of ? phase (Mg), ρ (CuMg₂), δ (Mg₂Ni) and Mg₃AlNi₂ was observed in both configurations. Maximum shear strength obtained was 57 MPa for Mg–AZ31/Ni–Cu/Ti–6Al–4V configuration and in both configurations, the increase in bonding time resulted in a decrease in joint strength to 13 MPa. The mechanism of joint formation includes three stages; solid state diffusion, dissolution and widening of the joint, and isothermal solidification.     

Mechanical milling of Ti–Ni–Si filler metal for brazing TiAl intermetallics

The Ti–Ni–Si filler metal was manufactured by mechanical milling of TiH₂, Ni and Si powder mixture. The microstructure of the filler metal and TiAl brazed joint was analyzed by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The effect of milling time on the brazing powder was investigated. It was found that NiSi phase formed when the milling time exceeded 120 min. The typical microstructure of the TiAl brazed joint using Ti–Ni–Si filler metal was TiAl/Ti₃Al/TiAlNi₂/Ti₃Al + Ti₅Si₃/TiAlNi₂/Ti₃Al/TiAl. The effect of Si on the microstructure was investigated and the result suggested that Si addition resulted in the aggregation of Ti and formation of Ti₃Al phase in the middle of joint. The optimal parameters were brazing temperature of 1140 °C and holding time of 30 min. The fracture was brittle and propagated between the TiAlNi₂ layer and Ti₃Al + Ti₅Si₃ layer.     

Nb、Cu金属层厚度对Si3N4/Nb/Cu/Ni/Incone l600接头组织和性能的影响

采用Nb／Cu／Ni作中间层，在连接温度为1403K、连接时间为50min、连接压力为7．5MPa的条件下，采用不同尺寸的中间层进行了Si3N4陶瓷与Inconel 600高温合金的部分液相扩散连接。通过改变Nb层、Cu层厚度，研究了Cu层、Nb层厚度变化对Si3N4／Nb／Cu／Ni／Inconel 600接头的组织和性能的影响。研究发现，当Cu层厚度小于0．05mm时，随着Cu层厚度的增加，接头中的Cu—Ni合金层厚度增加，接头强度快速增加；当Cu层厚度超过0．05mm时，接头中的Cu—Ni合金层厚度由于压力的作用不明显增加，接头强度增加缓慢。随着Nb层厚度的增加，反应层厚度增加，接头的强度先增大后减小。     

Cu + TiB2 composite filler for brazing Al2O3 and Ti-6Al-4V alloy

Al₂O₃ and Ti-6Al-4V alloy were brazed using Cu + TiB₂ composite filler, which manufactured by mechanical milling of Cu and TiB₂ powders. Typical interface microstructure of joint was Al₂O₃/Ti₄(Cu,Al)₂O/Ti₂Cu + Ti₃Al + Ti₂(Cu,Al)/Ti₂(Cu,Al) + AlCu₂Ti/Ti₂Cu + AlCu₂Ti + Ti₃Al + Ti₂(Cu,Al) + TiB/Ti(s.s) + Ti₂Cu/Ti-6Al-4V alloy. Based on temperature- and time-dependent compositional change, the formation of intermetallics in joint was basically divided into four stages: formation of interfacial Ti₄(Cu,Al)₂O in Al₂O₃ side, formation of Ti₂Cu, Ti₃Al, TiB, Ti₂Cu, and AlCu₂Ti in layers II and IV, formation of Ti₂(Cu,Al) and AlCu₂Ti in layer III, formation of Ti + Ti₂Cu hypereutectoid organization adjacent to Ti-6Al-4V alloy. TiB in situ synthesized in joint not only acted as low thermal expansion coefficient reinforcement to improve the mechanical properties at room temperature, but also as skeleton ceramic of joint to increase high temperature mechanical properties of Al₂O₃/Ti-6Al-4V alloy joint increasing. When the joint containing 30 vol.% TiB brazed at 930 °C and 10 min of holding time, the maximum room temperature shear strength of joint was 96.76 MPa, and the high temperature shear strength of joint was 115.16 MPa at 800 °C.     

Microstructure and mechanical properties of ZrB2–SiC ultrahigh temperature ceramic composite joint using TiZrNiCu filler metal

Abstract

ZrB₂–SiC ceramic composite was brazed by using TiZrNiCu active filler metal. The microstructure and interfacial phenomena of the joints were analysed by means of SEM, energy dispersive X-ray spectroscopy and X-ray diffraction. The joining effect was evaluated by shear strength. The results showed that the reaction products of the ZrB₂–SiC ceramic composite joint were TiC, ZrC, Ti₅Si₃, Zr₂Si, Zr(s,s) and (Ti, Zr)₂ (Ni, Cu), and the microstructure was separately ZrB₂–SiC/Zr(s,s)/Ti₅Si₃+Zr₂Si+TiC+ZrC+(Ti,Zr)₂(Ni,Cu)/Zr(s,s)/ZrB₂–SiC. A conceptual interface evolution model was established to explain the interface evolution mechanism. The maximum shear strength of the brazed joints was 143·5 MPa at the brazing temperature T of 920°C and the holding time t of 10 min.     

Formation of Brittle Phases During Pulsed Current Gas Tungsten Arc Welding of Titanium to Aluminum Alloys

Welding of titanium alloy TA15 to aluminum alloy Al 2024 was conducted by pulsed current gas tungsten arc welding using AlSi12 filler metal. Formation process of phases near the Ti/Al interface was discussed. Titanium and aluminum were partially fusion welded in the upper part while brazed together in the middle and bottom parts of the joint. In the upper part of the joint, intermetallics Ti₃Al + Ti₅Si₃, TiAl + Ti₅Si_3, and TiAl₃ were formed as three layers orderly from the titanium side to the weld metal. In the middle and bottom parts of the joint, intermetallics Ti₅Si₃ and TiAl₃ were formed as two layers near the Ti/Al interface.     

Ti活度对Al2O3/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响

采用AgCuTi钎料实现了Al₂O₃陶瓷与Fe-Co-Ni合金的钎焊连接,并调查了不同钛含量的钎料对Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响。扫描电子显微镜(SEM), X射线能量色散光谱仪(EDS), X射线衍射仪(XRD)及电子万能试验机用于分析钎焊接头的机械性能和微观组织结构,结果表明:钛含量的增加明显提高AgCuTi钎料与Al₂O₃陶瓷的相互作用,在Al₂O₃/Ag-Cu-Ti界面生成一层由Ti-Al 和 Ti-O化合物组成的反应层。Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头的抗拉强度随钛含量的增加而增加,当钛含量提高到8wt.%时,抗拉强度达到最大值78Mpa。通过微观组织结构分析发现,采用AgCu4Ti在890℃保温5min的条件下可以获得较好的钎焊接头,典型接头的微观组织结构为Al₂O₃/TiAl+Ti₃O₅/NiTi+Cu₃Ti+Ag(s,s)/Ag(s,s)+Cu(s,s)+(Cu,Ni)/Fe-Ni-Co。采用AgCu8Ti获得的钎焊接头的界面反应层与AgCu4Ti差异不大,但反应层稍微增厚,并伴有TiO和Ti3Al在Al₂O₃/Ag-Cu-Ti界面生成。     

保温时间对瞬时液相扩散连接的Ti3Al /Ti2AlNb接头微观结构及力学性能的影响

采用Ni-Ti复合箔片作为中间层,在990 ℃、低连接压力（0.1 MPa）下,通过瞬时液相（TLP）扩散连接制备了Ti₃Al/Ti₂AlNb异种合金接头。分析了保温时间（10~90 min）对Ti₃Al/Ti₂AlNb接头微观结构及力学性能的影响,并研究了TLP扩散连接接头的界面演变和形成机制。结果表明,Ti₃Al/Ti₂AlNb接头具有典型的“Ti₃Al | Al_0.5Nb_0.5Ti₃ | 残余 Ni | NiTi | NiTi₂ | 残余 Ti | Al_0.5Nb_0.5Ti₃ | Ti₂AlNb”多层梯度结构。随着保温时间的延长,接头的抗剪切强度先增大后减小,当保温时间达到60 min时,Ti₃Al/Ti₂AlNb接头的抗剪切强度最大,达到167±12 MPa。另外,接头的断裂主要发生在Ti₂AlNb/Ti附近的NiTi₂层,并向Ti层延伸,呈现出脆性断裂的特征。     

Joining of Cf/SiC Composite and TC4 Using Ag-Al-Ti Active Brazing Alloy

Carbon fiber reinforced SiC (C_f/SiC) composite was successfully joined to TC4 with Ag-Al-Ti alloy powder by brazing. Microstructures of the brazed joints were investigated by scanning electron microscope, energy dispersive spectrometer, and x-ray diffraction. The mechanical properties of the brazed joints were measured by mechanical testing machine. The results showed that the brazed joint mainly consists of TiC, Ti₃SiC₂, Ti₅Si₃, Ag, TiAl, and Ti₃Al reaction products. TiC + Ti₃SiC₂/Ti₅Si₃ + TiAl reaction layers are formed near C_f/SiC composite while TiAl/Ti₃Al/Ti + Ti₃Al reaction layers are formed near TC4. The thickness of reaction layers of the brazed joint increases with the increased brazing temperature or holding time. The maximum room temperature and 500 °C shear strengths of the joints brazed at brazing temperature 930 °C for holding time 20 min are 84 and 40 MPa, respectively.     

Reaction layer characterization of the braze joint of silicon nitride to stainless steel

This investigation studies the role of titanium in the development of the reaction layer in braze joining silicon nitride to stainless steel using titanium-active copper-silver filler metals. This reaction layer formed as a result of titanium diffusing to the filler metal/silicon nitride interface and reacting with the silicon nitride to form the intermetallics, titanium nitride (TiN) and titanium suicide (Ti ₅Si₃). This reaction layer, as recognized in the literature, allows wetting of the ceramic substrate by the molten filler metal. The reaction layer thickness increases with temperature and time. Its growth rate obeys the parabolic relationship. Activation energies of 220.1 and 210.9 kj/mol were calculated for growth of the reaction layer for the two filler metals used. These values are close to the activation energy of nitrogen in TiN (217.6 kj/mol). Two filler metals were used in this study, Ticusil (68.8 wt% Ag, 26.7 wt% Cu, 4.5 wt% Ti) and CB4 (70.5 wt% Ag, 26.5 wt% Cu, 3.0 wt% Ti). The joints were processed in vacuum at temperatures of 840 to 900 °C at various times. Bonding strength is affected by reaction layer thickness in the absence of Ti-Cu intermetallics in the filler metal matrix.     

Formation and properties of Ti-based Ti–Zr–Cu–Fe–Sn–Si bulk metallic glasses with different (Ti + Zr)/Cu ratios for biomedical application

Ti-based Ti–Zr–Cu–Fe–Sn–Si bulk metallic glasses (BMGs) free from highly toxic elements Ni and Be were developed as promising biomaterials. The influence of (Ti + Zr)/Cu ratio on glass-formation, thermal stability, mechanical properties, bio-corrosion resistance, surface wettability and biocompatibility were investigated. In the present Ti-based BMG system, the Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy exhibited the highest glass forming ability (GFA) corresponding to the largest supercooled liquid region, and a glassy rod with a critical diameter of 3 mm was prepared by copper-mold casting. The Ti-based BMGs possess high compressive strength of 2014–2185 MPa and microhardness of 606–613 Hv. Young's modulus of the Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy was about 100 GPa, which is slightly lower than that of Ti–6Al–4V alloy. The Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy with high GFA exhibited high bio-corrosion resistance, and good surface hydrophilia and cytocompatibility. The mechanisms for glass formation as well as the effect of (Ti + Zr)/Cu ratio on bio-corrosion behavior and biocompatibility are discussed.     

Microstructure and mechanical properties of the SiC/Nb joint brazed using AgCuTi+B4C composite filler metal

The residual stress is considered to be the driving force for the failure of ceramic/metal brazing joint. In this paper, the residual stress in a SiC/Nb joint is alleviated by using AgCuTi+B₄C composite brazing filler. SEM, EDS and XRD are applied to characterised the microstructure of the joint, which is determined to be SiC/Ti₃SiC₂/Ag(s,s)+Cu(s,s)+TiB+TiC/TiCu+ Nb(s,s)/Nb. The effects of the B₄C strengthening phase mass fraction and the brazing temperature on the microstructure and the mechanical properties of the joint are investigated. It is found that the reaction products between B₄C and the brazing filler (TiB whisker and TiC particles) uniformly distribute inside the joint if the mass fraction of the B₄C is not higher than 1.5 wt% and when the amount of B₄C reaches 2 wt%, the reaction products begin to agglomerate. With the rising of the brazing temperature, the thickness of the Ti₃SiC₂ reaction layer next to the ceramic increases and when the brazing temperature reaches 910 °C, another reaction layer of Ti₅Si₃ can be found adjacent to the Ti₃SiC₂ reaction layer. The strength of the joint first increases and then decreases with the increase of both the strengthening phase and the brazing temperature. The highest shear strength of the joint reaches 98 MPa when the joint is achieved at 890 °C using AgCuTi+1.5 wt%B₄C brazing filler.     

Effect of Ti content in Ag–Cu–Ti activated filler metal on dissimilar joint formation of sialon and WC–Co alloy by laser brazing

Laser brazing was carried out for dissimilar joining of sialon and a WC–Co alloy. Eutectic type Ag–Cu alloys as filler metals with different Ti content ranging from 0 to 2·8 mass-% were used to investigate the effects of Ti on the interface structure and strength of the joint. The filler metal sheet was sandwiched between a sialon block and a WC–Co alloy plate, and a laser beam was irradiated selectively on the WC–Co alloy plate. The brazed joint was obtained using the filler metal containing >0·3 mass-%Ti. TiN, Ti₅Si₃, and Cu₄Ti layers were formed at the interface of sialon and brazed metal as compound layers. The shear strength of the brazed joint increased with increasing Ti content in the filler metal in the range 0·3–1·7 mass-%, reaching a maximum value of 106 MPa. However, the strength decreased when the Ti content became higher than 1·7 mass-%.     

Cf/Al复合材料与TC4钛合金的激光诱导燃烧合成连接

采用激光诱导燃烧合成连接方法实现Cf/Al复合材料和TC4钛合金的可靠连接.放热中间层的燃烧合成反应为连接过程提供所需能量.结合理论计算和实验,对Ni?Al?Zr中间层的化学成分进行优化设计,并对连接接头的显微组织和力学性能进行研究.结果表明,Zr的加入轻微降低中间层的放热性,但显著提高连接质量,是实现可靠连接的关键....     

Microstructure and mechanical properties of Cu/Al joints brazed using (Cu,Ni, Zr,Er)-modified Al—Si filler alloys

To design a promising Al—Si filler alloy with a relatively low melting-point, good strength and plasticity for the Cu/Al joint, the Cu, Ni, Zr and Er elements were innovatively added to modify the traditional Al—Si eutectic filler. The microstructure and mechanical properties of filler alloys and Cu/Al joints were investigated. The result indicated that the Al—Si—Ni—Cu filler alloys mainly consisted of Al(s,s), Al₂(Cu,Ni) and Si(s,s). The Al—10Si—2Ni—6Cu filler alloy exhibited relatively low solidus (521 °C) and liquidus (577 °C) temperature, good tensile strength (305.8 MPa) and fracture elongation (8.5%). The corresponding Cu/Al joint brazed using Al—10Si—2Ni—6Cu filler was mainly composed of Al₈(Mn,Fe)₂Si, Al₂(Cu,Ni)₃, Al(Cu,Ni), Al₂(Cu,Ni) and Al(s,s), yielding a shear strength of (90.3±10.7) MPa. The joint strength was further improved to (94.6±2.5) MPa when the joint was brazed using the Al—10Si—2Ni—6Cu—0.2Er—0.2Zr filler alloy. Consequently, the (Cu, Ni, Zr, Er)-modified Al—Si filler alloy was suitable for obtaining high-quality Cu/Al brazed joints.     

Vacuum brazing of TiAl-based intermetallics with Ti–Zr–Cu–Ni–Co amorphous alloy as filler metal

An amorphous Ti41.7–Zr26.7–Cu14.7–Ni13.8–Co3.1 (wt%) ribbon fabricated by melt spinning was used as filler to vacuum braze Ti–48Al–2Nb–2Cr (at%) intermetallics. The influences of brazing temperature and time on the microstructure and strength of the joints were investigated. It is found that intermetallic phases of Ti₃Al and γ-Ti₂Cu/Ti₂Ni form in the brazed joints. The tensile strength of the joint first increases and then decreases with the increase of the brazing temperature in the range of 900–1050 °C and the brazing time varying from 3 to 15 min. The maximum tensile strength at room temperature is 316 MPa when the joint is brazed at 950 °C for 5 min. Cleavage facets are widely observed on all of the fracture surfaces of the brazed joints. The fracture path varies with the brazing condition and cracks prefer to initiate at locations with relatively high content of γ-Ti₂Cu/Ti₂Ni phases and propagate through them.     

Oxidation Behavior of Ti50Ni40Cu10 Shape-Memory Alloy in 700–1,000 °C Air

The isothermal-oxidation behavior of Ti₅₀Ni₄₀Cu₁₀ shape memory alloy (SMA) in 700–1,000 °C air was investigated by TGA, XRD, SEM and EPMA. Experimental results indicate that a multi-layered oxide scale formed, consisting of an outermost Cu₂O(Ni,Ti) layer, a layer of the mixture of TiO₂, TiNiO₃ and irregular small pores, a layer of the mixture of Ni(Ti,Cu), TiO₂ and irregular large pores, a Ti(Ni,Cu)₃ layer and an innermost Ti₃₀Ni_43–47Cu_27–23 layer. The apparent activation energy for the oxidation reaction of Ti₅₀Ni₄₀Cu₁₀ SMA is determined to be 180 kJ/mol, and the oxidation rate follows a parabolic law. A schematic oxidation mechanism of Ti₅₀Ni₄₀Cu₁₀ SMA is proposed to explain the observed results.     

Behaviors of interfacial elements during the brazing of SiO2 glass ceramic to Ti-6Al-4V with AgCu/Ni interlayer

AgCu/Ni composite interlayer was used to join SiO₂ glass ceramic to Ti-6Al-4V alloy successfully, obtaining the largest joint shear strength 110MPa. Ag, Cu and Ni in the interlayer and Ti in the Ti-6Al-4V alloy affect the joint formation and interfacial products significantly. To understand the joint formation process better, behaviors of elements Ag, Cu, Ni and Ti during the brazing of SiO₂ glass ceramic to Ti-6Al-4V alloy were investigated in the present work. Active element Ti is the most important component in the joining, realizing the metallurgical bonding of SiO₂ glass ceramic to braze alloy. Cu together with Ni reacts to Ti in the base material by Ti-Cu-Ni ternary eutectic reaction, which is beneficial for reducing the massive Ti-Cu and/or Ti-Ni brittle intermetallic compounds on the joint interface. Dispersion of Ag decreases the brittleness of the whole joint effectively.