AgCuTi-Al钎焊C_f/SiC与TC4接头分析

采用AgCuTi-Al混合粉末作为中间层,在适当的工艺参数下真空钎焊Cf/SiC复合材料和钛合金,利用扫描电镜,能谱仪和X射线衍射对接头的微观组织结构进行分析,利用剪切试验测定接头的力学性能.结果表明,在钎焊过程中,钎料中的钛与Cf/SiC复合材料中的基体SiC,碳纤维发生反应,在Cf/SiC复合材料侧形成了TiC,T...     

C_f/SiC复合材料与钛合金Ag-Cu-Ti-C_f复合钎焊

采用Ag-Cu-Ti-Cf(Cf:碳纤维)复合钎料作中间层,在适当的工艺参数下真空钎焊Cf/SiC复合材料与钛合金,利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.结果表明,钎焊时复合钎料中的钛与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面形成Ti3SiC2,Ti5Si3和少量TiC化合物的混合反应层.复合钎料中的铜与钛合金中的钛发生互扩散,在连接层与钛合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成碳纤维强化的致密复合连接层.碳纤维的加入缓解了接头的残余热应力,Cf/SiC/Ag-Cu-Ti-Cf/TC4接头抗剪强度明显高于Cf/SiC/Ag-Cu-Ti/TC4接头.     

Cf/SiC复合材料与钛合金(Ti-Zr-Cu-Ni)+W复合钎焊分析

在适当的工艺参数下,用(Ti-Zr-Cu-Ni)+W复合钎料真空钎焊Cf/SiC复合材料与钛合金,采用SEM,EDS和XRD分析接头组织结构,利用剪切试验检测接头的力学性能.结果表明,钎焊时复合钎料中的钛、锆与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面生成Ti3SiC2,Ti5Si3和少量TiC(ZrC)化合物的混合反应层,在连接层与钛合金界面形成Ti-Cu化合物扩散层.增强相钨粉能有效缓解接头的残余热应力,提高接头力学性能,在连接温度930℃,保温时间20 min的工艺条件下,增强相钨粉含量为15%(体积分数)时,接头抗剪强度最高为166 MPa.     

Interfacial Behavior and Its Effect on Mechanical Properties of C<Subscript>f</Subscript>/SiC Composite/TiAl6V4 Joint Brazed with TiZrCuNi

In order to characterize the interfacial behavior of brazed joints and offer theoretical basis for the applications of TiZrCuNi-based composite fillers, C_f/SiC composite and TC4 were brazed by TiZrCuNi filler, and the microstructures of joints versus temperature and versus holding time were systematically studied in this paper. The mechanical properties of brazed joints were measured and analyzed. The results showed that Ti(Zr)C, Ti₅Si₃, Ti₂Cu, TiNi, TiZrCu₂, Ti₂(Cu,Ni) and Ti(s,s) were the predominant compounds in the joints. Brazing temperature had a distinct effect on the microstructures of joints: with the increase of brazing temperature, the structure of brazed joints was reduced from four parts to three parts, and the wavy reaction layer became continuous and much thicker. While holding time had a similar but weaker effect on microstructures: with the extension of holding time, the reaction layer became thicker, but it was difficult to induce the decrease in the structural parts of joint. The thickness of reaction layer determined the mechanical properties of joints. The results were beneficial for the selection of reinforced phases and the design of composite fillers to obtain better mechanical performances. When the brazing temperature was 940 °C and the holding time was 25 min, the maximum shear strength of brazed joints attained a value of 143.2 MPa.     

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.     

Interfacial reaction studies of B4C-coated and C-coated SiC fiber reinforced Ti–43Al–9V composites

The interfacial reactions of B₄C-coated and C-coated SiC fiber reinforced Ti–43Al–9V composites were investigated by scanning electron microscope and transmission electron microscope. The detailed microstructures as well as the chemical composition throughout the reaction zone were identified. For SiC_f/B₄C/TiAl composite, the reaction zone from B₄C coating to TiAl matrix is composed of 4 layers, namely, a carbon-rich layer, a mixed layer of TiB₂ + amorphous carbon, a TiC layer and a mixed layer of TiB + Ti₂AlC. For SiC_f/C/TiAl composite, the reaction zone from C coating to TiAl matrix is composed of 3 layers, namely, a fine-grained TiC layer, a coarse-grained TiC layer and a thick Ti₂AlC layer. For both kinds of composites, the reaction mechanisms of the interfacial reactions were analyzed, and the corresponding reaction kinetics were calculated. The activation energies of interfacial reaction in SiC_f/B₄C/TiAl composite and SiC_f/B₄C/TiAl composite are 308.1 kJ/mol and 230.7 kJ/mol, respectively.     

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.     

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.     

Effect of brazing temperature and brazing time on the microstructure and tensile strength of TiAl-based alloy joints with Ti-Zr-Cu-Ni amorphous alloy as filler metal

An amorphous Ti-37.5Zr-15Cu-15Ni (wt.%) ribbon fabricated by vacuum arc remelting and rapid solidification was used as filler metal to vacuum braze TiAl alloy (Ti-45Al-2Mn-2Nb-1B (at.%)). The effects of brazing temperature and time on the microstructure and strength of the joints were investigated in details. The typical brazed joint major consisted of three zones and the brazed joints mainly consisted of α_2-Ti₃Al phase, α-Ti phase and (Ti, Zr)₂(Cu, Ni) phase. When the brazing temperature varied from 910 °C to 1010 °C for 30 min, the tensile strength of the joint first increased and then decreased. With increasing the brazing time, the tensile strength of the joint increased. The maximum room temperature tensile strength was 468 MPa when the specimen was brazed at 930 °C for 60 min. All the fracture surfaces assumed typical brittle cleavage fracture characteristic. The fracture path varied with the brazing parameter and cracks preferred to initiate at (Ti, Zr)₂(Cu, Ni) phase and propagation path were mainly determined by the content and distribution of α-Ti phase and (Ti, Zr)₂(Cu, Ni) phase.     

采用Ti/Ag-Cu/Cu中间层钎焊连接Si3N4陶瓷和TiAl合金的界面结构及性能

采用Ti/Ag-Cu/Cu中间层实现了Si₃N₄陶瓷与TiAl合金的钎焊连接,获得了良好的接头.利用SEM,EDS等微观手段,分析了接头界面结构和元素分布情况.结果表明,Si₃N₄陶瓷/Ti/Ag-Cu/Cu/TiAl典型界面微观结构可能为:Si₃N₄/TiN/Ti-Si/Cu-Ti+Ag（s,s）+Cu（s,s）/AlCuTi/TiAl.在连接温度1 133 K、保温时间30 min、接头压力0.040 MPa时,接头四点弯曲强度达到最大值170 MPa.     

Interfacial features of TiAl alloy/316L stainless steel joint brazed with Zr−Cu−Ni−Al amorphous filler metal

TiAl alloy and 316L stainless steel were vacuum-brazed with Zr?50.0Cu?7.1Ni?7.1Al (at.%) amorphous filler metal. The influence of brazing time and temperature on the interfacial microstructure and shear strength of the resultant joints was investigated. The brazed seam consisted of three layers, including two diffusion layers and one residual filler metal layer. The typical microstructure of brazed TiAl alloy/316L stainless steel joint was TiAl alloy substrate/α₂-(Ti₃Al)/AlCuTi/residual filler metal/Cu₉Zr₁₁+Fe₂₃Zr₆/Laves-Fe₂Zr/α-(Fe,Cr)/316L stainless steel substrate. Discontinuous brittle Fe₂Zr layer formed near the interface between the residual filler metal layer and α-(Fe,Cr) layer. The maximum shear strength of brazed joints reached 129 MPa when brazed at 1020 °C for 10 min. The diffusion activation energies of α₂-(Ti₃Al) and α-(Fe,Cr) phases were ?195.769 and ?112.420 kJ/mol, respectively, the diffusion constants for these two phases were 3.639×10^?6 and 7.502×10^?10 μm²/s, respectively. Cracks initiated at Fe₂Zr layer and propagated into the residual filler metal layer during the shear test. The Laves-Fe₂Zr phase existing on the fracture surface suggested the brittle fracture mode of the brazed joints.     

SiCp/Al复合材料与Fe36Ni合金超声波钎焊

利用超声波钎焊方法使用ZnAlSi钎料实现了Fe36Ni合金与45%SiC_p/2024Al和55%SiC_p/A356两种复合材料的连接,并得到由SiC颗粒增强的复合焊缝.通过扫描电镜、能谱等方法对焊缝的微观结构以及断口形貌进行了观察,对接头的压剪强度进行了测试,分析了Fe36Ni与两种复合材料钎焊接头微观组织和接头强度的差异.结果表明,在Fe36Ni与两种复合材料的钎缝中,钎料与两侧母材界面均形成良好的冶金结合,SiC颗粒均匀分布于焊缝中.Fe36Ni与45%SiC_p/2024Al的接头抗剪强度为110~145 MPa,Fe36Ni与55%SiC_p/A356的接头抗剪强度为75~85 MPa.Fe36Ni与45%SiC_p/2024Al的接头断裂位置为钎缝中,而Fe36Ni与55%SiC_p/A356的接头断裂位置位于Fe36Ni与钎料的界面上.     

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.     

Reaction diffusion in continuous SiC fiber reinforced Ti matrix composite

SiC continuous fiber-reinforced pure Ti(TA1)matrix composites were fabricated by a vacuum hot pressing(VHP)methodand then heat-treated in vacuum under different conditions.The interfacial reaction and the formation of interfacial phases werestudied by using SEM,EDS and XRD.The results show that there exists reaction diffusion at the interface of SiC fibers and Timatrix,and the concentration fluctuation of reaction elements such as C,Ti and Si appears in interfacial reaction layer.The interfacialreaction products are identified as Ti3SiC2,TiCx and Ti5Si3Cx.At the beginning of interfacial reaction,the interfacial reactionproducts are TiCx and Ti5Si3Cx.Along with the interfacial reaction diffusion,Ti3SiC2 and Ti5Si3Cx single-phase zones come forth inturn adjacent to SiC fibers,and the TiC Ti5Si3Cx double-phase zone appears adjacent to Ti matrix,which forms discontinuousconcentric rings by turns around the fibers.The formed interfacial phases are to be Ti3SiC2,Ti5Si3Cx and TiCx Ti5Si3Cx from SiCfiber to Ti matrix.The interfacial reaction layer growth is controlled by diffusion and follows a role of parabolic rate,and theactivation energy(Qk)and(k0)of SiC/TA1 are 252.163 kJ/mol and 7.34×10?3m/s1/2,respectively.     

Ag-Cu-Sn-Ti活性钎焊Gr/2024Al复合材料与TC4钛合金

采用自制的AgCuSnTi钎料对发汗材料Gr/2024Al复合材料和TC4钛合金进行钎焊,对焊后接头界面组织及力学性能进行了分析.结果表明,接头典型界面组织为Gr/2024Al/Ti₃AlC₂/Ag₂Al+Ag₃Sn+Al₂Cu+Al₅CuTi₂/Al₅CuTi₂+Ag₃Sn/TC4.钎焊时,活性元素Ti与Gr/2024Al复合材料的石墨基体发生活性反应,实现了TC4与Gr/2024Al复合材料的低温连接,保证了复合材料的力学性能及发汗功能.随钎焊温度升高及保温时间延长,钎缝组织中弥散分布的Al₅CuTi₂化合物聚集长大成块状,使接头性能下降.当钎焊温度为680℃,保温时间为10min时接头抗剪强度达到最大值17MPa,其为Gr/2024Al复合材料母材强度的70%.     

Reactive sintering of TiAl–Ti5Si3 in situ composites

TiAl with between 0 and 20 vol%Ti₅Si₃ was produced by reactive sintering (700 °C for 15 min in vacuum) of cold pressed compacts of elemental Ti, Al and Si powder. The results show that adding Si to Ti and Al reduces the swelling associated with reactive sintering of TiAl, as composites containing more than 5 vol%Ti₅Si₃ densified during reactive sintering. However, composites containing more than 10 vol%Ti₅Si₃ did not retain their shape and the TiAl+20 vol%Ti₅Si₃ composite completely melted during the sintering process. A thermodynamic analysis indicated that the simultaneous formation of TiAl and Ti₅Si₃ increases the adiabatic flame temperature during the reaction between the powders. In fact, the analysis predicted that the maximum temperature of the reaction associated with the formation TiAl+20 vol%Ti₅Si₃ should exceed the melting point of TiAl, and this was observed experimentally. Differential thermal analysis (DTA) revealed that an Al–Si eutectic reaction occurred in mixtures of Ti, Al and Si powders prior to the formation of the TiAl and Ti₅Si₃ phases. There was no such pre-reaction formation of a eutectic liquid in Ti and Al powder mixtures. The formation of the pre-reaction liquid and the increase in adiabatic flame temperature resulted in the melting that occurred and the enhanced densification (minimization of swelling) during reactive sintering of the in situ composites.     

Ag-Cu+WC复合钎料钎焊ZrO2陶瓷和TC4合金

采用新型Ag-Cu+WC复合钎料进行ZrO₂陶瓷和TC4合金钎焊连接,探究了接头界面组织及形成机制,分析了钎焊温度对接头界面结构和力学性能的影响. 结果表明,接头界面典型结构为ZrO₂/TiO+Cu₃Ti₃O/TiCu+TiC+W+Ag_(s,s)+Cu_(s,s)/TiCu₂/TiCu/Ti₂Cu/TC4. 钎焊过程中,WC颗粒与Ti发生反应,原位生成TiC和W增强相,为Ti-Cu金属间化合物、Ag基和Cu基固溶体提供了形核质点,同时抑制了脆性Ti-Cu金属间化合物的生长,优化了接头的微观组织和力学性能. 随钎焊温度的升高,接头反应层的厚度逐渐增加,WC颗粒与Ti的反应程度增强. 当钎焊温度890 ℃、保温10 min时,复合钎料所得接头抗剪强度达到最高值82.1 MPa,对比Ag-Cu钎料所得接头抗剪强度提高了57.3%.     

生成相性质及其对TiAl合金/42CrMo钢钎焊接头力学性能影响

在钎焊温度1123~1273 K,保温时间120~1500 s参数范围内对TiAl合金与42CrMo钢进行了真空扩散钎焊.用光学显微镜、扫描电镜和能谱分析等方法对界面组织进行了分析,用图像分析软件工具测量了反应层厚度;采用纳米压痕仪和显微硬度仪对TiAl合金/42CrMo钢钎焊接头的两种母材和接头界面反应相进行了硬度测试,对结果进行了对比,为了确定接头的薄弱环节,进行了扫描电镜原位观察下的接头拉伸试验.结果表明,AlCuTi,Ti₃Al,AlCu₂Ti和TiC的硬度较高,而银的固溶体硬度较低;纳米压痕的硬度结果比显微硬度值略高;扫描电镜下的原位拉伸试验结果表明,Al-Cu-Ti系反应层在受外力作用下容易发生脆性断裂,为接头的薄弱环节.     

钎料形态对半固态加压反应钎焊接头的影响

采用自制不同形态的Al-Si-Mg-Cu-Ti钎料对70% SiC_p/Al复合材料进行了半固态加压反应钎焊,阐述了该焊接方法的内涵,分析了接头组织性能. 结果表明,填充粉末钎料时,钎缝组织为铝合金基体、深灰色环状和块状Ti₇Al₅Si₁₂和块状Ti;填充片状钎料时,钎缝组织为铝合金基体和短棒状Ti₇Al₅Si₁₂. 接头界面结合情况是影响接头性能的主要因素. 填充粉末钎料时,钎料与母材结合充分,原子扩散通道多,接头界面结合好,没有明显分界线,接头力学性能好,抗剪强度达92.1 MPa,断口属于韧脆混合断口;填充片状钎料时,界面处有明显分界线,接头力学性能差,抗剪强度为43.9 MPa,断口为脆性断口.     

Infrared brazing of Ti–6Al–4V using two silver-based braze alloys

Infrared brazing of Ti–6Al–4V using two silver-based alloys is evaluated in the study. For the 72Ag–28Cu brazed specimen, Ag-rich matrix, eutectic Ag–Cu and Cu–Ti interfacial reaction layer(s) are observed in the experiment. In contrast, both Ag-rich matrix and interfacial titanium aluminides, TiAl or Ti₃Al, are found in the 95Ag–5Al brazed joint. In general, the shear strength of 72Ag–28Cu brazed joint is much higher than that of 95Ag–5Al brazed specimen. Additionally, the use of infrared brazing with lower brazing temperature and/or less time can significantly decrease both dissolution of the substrate into molten braze as well as excessive growth of the interfacial reaction layer(s) in the joint. Therefore, infrared brazing has the potential to be applied in industry.