Ti6Al4V和Al2A12的扩散连接界面组织及力学性能

采用热等静压(HIP)工艺连接Al2A12和Ti6Al4V两种不同的航空航天用材料.利用扫描电镜、能谱仪和X射线衍射仪观察连接过渡区的微观组织和组成的演化,并测试其主要的力学性能.结果表明:采用热等静压制备这两种材料的界面连接好;Ti/Al反应层界面处形成了不同的金属间化合物,例如,Al_3Ti、TiAl_2和TiAl;连接接头处硬度为163 HV,界面连接处剪切强度达到了23 MPa,比只添加镀层而无中间层的连接强度提高了约17.9%,但低于带有中间层的连接强度.由于过烧和孔隙的形成使得断裂方式是脆性断裂.由此可知,在热等静压成形过程中异种材料的元素发生了相互扩散,在扩散连接处形成了不同的金属间化合物,这些金属间化合物影响连接处的力学性能.     

2A12铝合金粉末与TC4钛合金热等静压粉-固扩散连接北大核心

利用热等静压(Hot Isostatic Pressing,HIP)工艺实现2A12铝合金粉末和Ti-6Al-4V钛合金的HIP粉-固扩散连接,对比研究了Cu作为中间层材料对扩散连接性能的影响。结果表明:对于2A12铝合金粉末和Ti-6Al-4V钛合金直接HIP扩散连接其连接接头处生成了3种不同的金属间化合物,这些化合物的存在对扩散连接接头的连接质量有有害的影响;当以Cu作为中间层时,扩散主要发生在Cu/Al一侧,Cu/Al共晶反应生成的液相渗透到铝合金粉末颗粒之间。当以Cu作为中间层时,扩散连接区域的硬度下降,剪切强度增加,和直接扩散连接相比,剪切强度增加了64%,达到23 MPa。     

MHC/GH4099热等静压扩散焊接头组织演化及断裂机制

实验研究了不同中间层(Ni-Cr-Si-B、Ag-Cu-Ti、Ti-Cr-Ni、Nb-Ni)对MHC与GH4099合金热等静压扩散焊工艺(HIP-DB)下接头力学性能的影响。在热等静压工艺为1 150℃/130 MPa/180 min时,采用Nb-Ni中间层获得了可靠的MHC/GH4099焊接接头。采用Nb-Ni中间层的接头抗拉/抗剪强度达到84/41 MPa,高于采用Ni-Cr-Si-B、Ag-Cu-Ti和Ti-Cr-Ni中间层的连接强度。其扩散诱导反应层为Mo-Nb固溶体、Ni₈Nb、Ni₃Nb和Ni₆Nb₇,对其强度和厚度进行了测定,以建立界面微观结构与接头性能的相关性。研究发现,析出相Ni₃Nb强度高、塑性好,对接头高温性能有益,裂纹从Mo-Nb固溶体处萌生,沿晶扩展至中间扩散层。     

2A12铝合金粉末与TC4钛合金热等静压粉-固扩散连接

利用热等静压(Hot Isostatic Pressing,HIP)工艺实现2A12铝合金粉末和Ti-6A1-4V钛合金的HIP粉-固扩散连接,对比研究了Cu作为中间层材料对扩散连接性能的影响.结果表明:对于2A12铝合金粉末和Ti-6A1-4V钛合金直接HIP扩散连接其连接接头处生成了3种不同的金属间化合物,这些化合...     

QAl10-4-4/TC6双金属连接界面组织与力学性能分析

铜合金/钛合金双金属材料能发挥各自的性能优势,兼具轻质、耐磨、高强等优异性能。本文通过真空热压扩散法连接QAl10-4-4铝青铜和TC6钛合金,并采用显微组织观察和剪切强度测试等方法,研究了直接连接和添加AgCuZnCd连接的QAl10-4-4/TC6双金属的界面组织和力学性能,探究了连接参数与中间层对QAl10-4-4/TC6双金属连接质量的影响规律,分析了双金属界面过渡层形成机理,建立了连接工艺-界面组织-力学性能的内在关联。结果表明：直接扩散连接的QAl10-4-4/TC6双金属连接质量较差,生成的金属间化合物导致界面上生长了贯穿长裂纹,剪切强度仅有21 MPa;添加AgCuZnCd连接QAl10-4-4/TC6双金属后界面金属间化合物减少,当连接温度为850 ℃时,界面剪切强度最大为178.19 MPa,温度超过850 ℃时,双金属界面强度迅速降低。     

SiC纤维增强Ti/Ti_2AlNb叠层复合材料制备及界面行为研究

以SiC纤维、Ti箔、Ti_2AlNb箔为原材料,采用箔-纤维-箔方法,通过真空热压技术制备了SiCf/Ti/Ti_2AlNb叠层复合材料。利用扫描电子显微镜(SEM)、能谱分析仪(EDS)和X射线衍射仪(XRD)对复合材料相组成和微观组织进行了分析。结果表明,当真空热制造参数为920℃/40 MPa/30 min时,SiC纤维与韧性金属Ti实现良好冶金结合,界面反应产物主要为TiC,界面反应层厚度为0.8μm,C涂层厚度为1.3μm;韧性金属Ti层与金属间化合物Ti_2AlNb层通过Ti,Al,Nb 3种元素相互扩散方式形成固相扩散连接,界面平直,复合材料呈现出理想叠层结构。制备态的SiCf/Ti/Ti_2AlNb叠层复合材料主要由α-Ti,β-Ti,SiC,TiC,O相和B2相构成。在Ti与Ti_2AlNb固相扩散连接过程中,由于Al原子的扩散速率大于Nb原子,且Al是α稳定元素,Nb是β稳定元素,从而导致在Ti/Ti_2AlNb界面区域依次形成α+β双相组织和富B2相。在真空热压实验中,韧性金属Ti层与金属间化合物Ti_2AlNb层固相扩散连接过程依次为:物理接触/α+β双相区形成/富B2相区形成/富B2相区增厚。     

加热温度对镍中间层热轧钛钢复合板微观组织及力学性能的影响

以Ni为中间层制备钛/钢轧制复合板,借助扫描电镜、能谱仪、X射线衍射仪和Instron万能拉伸试验机等分析手段,研究了850～950℃加热温度对钛钢复合板力学性能和显微组织的影响。结果表明:当加热温度在850～900℃时,剪切强度随温度升高而升高;加热温度为900～950℃时,剪切强度随温度升高而降低,最高剪切强度都在900℃时获得。以Ni为中间层有效阻止了Fe和C等元素扩散到Ti侧形成金属间化合物,界面化合物种类不随温度变化,但化合物量随温度升高而增加。轧制温度为850℃时,界面上金属间化合物非常少,对应的剪切强度最低;轧制温度为900℃时,复合板界面剪切强度最优,与之相对应的界面结构是较为充分的元素扩散以及少量的金属间化合物;轧制温度为950℃时,金属间化合物层急剧变厚,TiNi_3和孔洞急剧增多,因而严重削弱了界面的剪切强度。     

CA-MIG热源处理下钛/铝异质合金界面显微组织特性

采用Al-Si5焊丝进行TC4钛/1060铝异质结构的CA-MIG连接,采用SEM、EDS等显微分析手段对不同热输入下所获接头的Ti/Al界面显微组织特点、界面附近元素分布进行分析,研究Ti/Al界面特性随热源热输入变化的演变规律。结果表明,CA-MIG热源热输入对Ti/Al界面显微组织具有显著影响。当热源热输入低于0.91 kJ/cm时,钛与铝基焊缝之间仅形成了一层界面反应层。当热源热输入处于0.91~1.55 kJ/cm时,钛与焊缝之间形成了两种Ti/Al界面,一种为单层结构的齿状Ti(Al,Si)₃;另一种由α-Ti(Al,Si)均匀层、Ti₅Si₃纳米颗粒+Ti(Al,Si)₃混合层、齿状Ti(Al,Si)₃层3层结构组成。当热源热输入超过1.55 kJ/cm后,除了上述两种Ti/Al界面外,局部微区钛合金发生熔化,与铝基焊缝之间形成了成分复杂的熔合区,熔合区内存在大量的裂纹缺陷。     

Al涂层/AZ91镁合金复合铸造界面的研究

对型芯预喷涂一层Al涂层,将AZ91镁合金液浇注到铸型中实现基体和涂层的结合,对凝固后的结合界面组织和相组成进行分析。结果表明,AZ91镁合金液和Al涂层表面的氧化物发生反应,实现了界面间的润湿,形成冶金结合界面。该界面包含3个扩散层:镁合金基体一侧为(Al12Mg17+δMg)共晶组织;中间层为Al12Mg17金属间化合物; Al涂层一侧为Al3Mg2金属间化合物,并弥散分布着一些氧化物。试验结果证明,通过复合铸造的方法可以实现Al涂层和镁合金基体的冶金结合。     

氮化硅陶瓷与金属热等静压扩散连接的研究

本文对热等静压方法进行Si_3N_4与碳钢的扩散连接过程进行了研究。考查了温度、时间,压力、陶瓷密度及表面粗糙度以及加入一层或两层Ti、Zr、Mo、Cu、Ni和Ni-Mo等中间层对连接强度的影响。检测了陶瓷金属连接的界面产物。结果表明,温度、压力、时间分别为1060～1340℃,50～150 Mpa,1～5 h范围变化时,Si_3N_4/钢界面都能产生很好的结合,连接体的强度随陶瓷密度的增加而提高。由于Ti、Zr、Mo中间层与Si_3N_4的反应产物分别为TiN,ZrN,Mo_5Si_3等脆性相,断裂总发生在陶瓷/金属界面上。中间层为Ni-Mo时,连接体具有最佳强度。     

机械合金化Ti/Al合金的制备

采用多维摆动式球磨机机械合金化Ti/Al二元粉末,研究了机械合金化过程中粉末结构的变化。Ti/Al混合粉末经高能球磨后,颗粒尺寸下降,Ti、Al晶粒各自逐渐细化至纳米级尺寸,且部分形成非晶,球磨15h后发现了TiAl和Ti3Al金属间化合物。将机械合金化后的粉末进行放电等离子烧结,烧结试样的组成相主要为TiAl和Ti3Al。     

Al/Cu Dissimilar Friction Stir Welding with Ni,Ti, and Zn Foil as the Interlayer for Flow Control,Enhancing Mechanical and Metallurgical Properties

This research investigates the effects of Ni, Ti, and Zn foil as interlayer, inserted between the faying edges of Al and Cu plates, for controlled intermetallic compound (IMC) formation. The weld tensile strength with Ti and Zn as interlayer is superior to Al base metal strength. This is due to controlled flow of IMCs by diffused Ti interlayer and thin, continuous, and uniform IMC formation in the case of Zn interlayer. Improved flexural stress was observed with interlayer. Weld microhardness varied with different interlayers and purely depends on IMCs present at the indentation point, flow of IMCs, and interlayer hardness. Specimens with interlayer failed at the interface of the nugget and thermomechanical-affected zone (TMAZ) with complete and broken three-dimensional (3-D) grains, indicating transgranular fracture. Phase analysis revealed that Al/Cu IMCs are impeded by Ni and Ti interlayer. The minor binary and ternary IMC phases form adjacent to the interlayer due to diffusion of the material with Al/Cu. Line scan and elemental mapping indicate thin, continuous, and uniform IMCs with enhanced weld metallurgical and mechanical properties for the joints with Zn interlayer. Macrostructural analysis revealed IMC flow variations with and without interlayer. Variation in grain size at different zones is also observed for different interlayers.     

Investigation on Metallurgical Structure and Mechanical Properties of Dissimilar Al 2024/Cu FSW T-joints

In this research, T-joining of AA2024-T4 and commercially pure copper were performed successfully using friction stir welding. Effect of welding parameters on metallurgical and mechanical characteristics of the joints was studied. For this purpose, tensile strength, microhardness, and macro- and microstructures of the joints were investigated. Also, the fracture surfaces were examined using XRD and SEM. The best results were obtained for the 1130 rpm rotation speed (ω) and 12 mm/min travel speed (v), with the UTS of 156 MPa (~70% of Cu strength). The microhardness test showed that TMAZ and base metal of Al side had the maximum hardness amounts (148 and 155 HV, respectively). Generally, increase in the ω²/v ratio caused the nugget zone and HAZ grain size to increase. The results revealed the formation of Al₂Cu and Al₄Cu₉ intermetallic compounds in the border zone of the joints. The fractography results showed the occurrence of cleavage fracture in all the samples.     

钛/铝复合板爆炸焊接技术研究进展

通过爆炸焊接技术制备的钛/铝复合板可兼具钛合金耐腐蚀性和铝合金低成本的优点。对钛/铝复合板爆炸焊接技术的研究进展进行介绍,论述了炸药种类、质量比R、基覆板间距及爆炸焊接窗口等主要工艺参数对钛/铝复合板组织和性能的影响;分析了影响钛/铝复合板结合界面的主要因素——金属间化合物种类、扩散层和界面波形;对钛/铝复合板硬度、抗剪切强度、抗拉强度及拉伸断口的研究进行了汇总分析。最后,指出了钛/铝复合板爆炸焊接工艺研究的重点发展方向。     

Ce、Nb对Al_(66)Mn_9Ti_(25)金属间化合物形变和断裂行为的影响

本工作研究了微量Ｃｅ、Ｎｂ对Ａｌ６６Ｍｎ９Ｔｉ２５金属间化合物显微组织、微裂纹生成及扩展倾向、维氏硬度、压缩性能、断裂特征、变形亚结构的影响。结果表明，添加微量Ｃｅ有显著的促进晶粒枝晶化和第二相弥散化作用，从而使微裂纹生成和扩展以及沿晶开裂受到一定程度的抑制，因而，压缩强度明显提高，压缩塑性也有改善。微量Ｎｂ的加入，显微组织仍保持等轴状晶粒和粗大第二相，压缩性能未能改善。     

A New Approach for Using Interlayer and Analysis of the Friction Welding of Titanium to Stainless Steel

Dissimilar material joining is often more difficult than joining the similar material or alloys with minor differences in physical properties and composition. The formation of deleterious intermediate phases consisting of intermetallic compounds during welding of titanium and stainless steel is a challenge to the welding processes, for decades. Friction welding has been used in an attempt to reduce formation of intermetallic compounds through inserting an interlayer material. In recent years, a number of approaches have been developed to insert interlayer between the substrates to avoid the metallurgical incompatibility. In this research, dissimilar joint of titanium and stainless steel were welded effectively using a new technique of electrodeposited nickel coating on one of the substrate (stainless steel) as interlayer. The bonding interface of the joints was characterized using optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Tensile strength of the nickel interlayer joints was higher than the direct joints. The microstructural characterization in the interface of titanium and stainless steel showed the absence of brittle Fe–Ti intermetallic compounds, which was a condition attributed to the use of interlayer technique. Whereas, the characterization of interface were identified as the presence of Ti–Ni phases which were more plastic than Fe–Ti intermetallic compounds.     

Interfacial microstructure and mechanical properties of diffusion-bonded joints of titanium TC4 (Ti-6Al-4V) and Kovar (Fe-29Ni-17Co) alloys

Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4(Ti-6 Al-4 V)and 4 J29 Kovar alloy(Fe-29 Ni-17 Co)were diffusely bonded by a vacuum hot-press sintering process in the temperature range of 700-850°C and bonding time of 120 min,under a pressure of 34.66 MPa.Interfacial microstructures and intermetallic compounds of the diffusion-bonded joints were characterized by optical microscopy,scanning electron microscopy,X-ray diffraction(XRD)and energy dispersive spectroscopy(EDS).The elemental diffusion across the interface was revealed by electron probe microanalysis.Mechanical properties of joints were investigated by micro Vickers hardness and tensile strength.Results of EDS and XRD indicated that(Fe,Co,Ni)-Ti,TiNi,Ti_2Ni,TiNi_2,Fe_2 Ti,Ti_(17) Mn_3 and Al_6 Ti_(19) were formed at the interface.When the bonding temperature was raised from 700 to 850°C,the voids of interface were reduced and intermetallic layers were widened.Maximum tensile strength of joints at 53.5 MPa was recorded by the sintering process at 850°C for 120 min.Fracture surface of the joint indicated brittle nature,and failure took place through interface of intermetallic compounds.Based on the mechanical properties and microstructure of the diffusion-bonded joints,diffusion mechanisms between Ti-6 Al-4 Vtitanium and Fe-29 Ni-17 Co Kovar alloys were analyzed in terms of elemental diffusion,nucleation and growth of grains,plastic deformation and formation of intermetallic compounds near the interface.     

Effect of Tool Offset and Tool Rotational Speed on Enhancing Mechanical Property of Al/Mg Dissimilar FSW Joints

Friction stir welding (FSW) is a promising solid-state joining technique for producing effective welds between Al alloy and Mg alloy. However, previously reported Al/Mg dissimilar FSW joints generally have limited strength or barely any ductility with relatively high strength, which was blamed on the brittle intermetallics formed during welding. In this study, effective joints with comparably high strength (163 MPa) and large elongation (~6 pct) were obtained. Three crucial/weak zones were identified in the welds: (1) Al/Mg bottom interface (BI) zone that resulted from the insufficient materials’ intermixing and interdiffusion; (2) banded structure (BS) zone which contains intermetallic particles possibly formed by constitutional liquation; and (3) softened Al alloy to the retreating side (SAA-RS) zone due to the dissolution and coarsening of the strengthening precipitates. Three fracture modes observed in the tensile specimens perpendicular to the weld seam were found closely related to these zones. Their microstructure evolution with the change of tool rotational speed and tool offset was characterized and the consequent effect on the fracture mode alteration was studied. It turned out that enhancing the strengths of all these zones, but keeping the strength of the SAA lowest, is an effective way for enhancing ductility while keeping comparatively high strength in Al/Mg FSW joints. Also, suggestions for further improving the mechanical property of the Al/Mg dissimilar FSW joints were made accordingly for practical applications.     

用于先进核能系统的12Cr-ODS铁素体钢的显微组织和力学性能

以12Cr-0.5Ti-1W的气雾化粉和纳米Y₂O₃粉末为原料,通过对预合金粉末的机械合金化和热等静压烧结成型的方法制备了12Cr-ODS铁素体钢,然后运用锻造和热处理等方法实现对材料力学性能的提高.在透射电子显微镜下观察到组织中弥散分布的纳米氧化物颗粒,能谱分析确定氧化物弥散颗粒为Y-Ti-O的复杂氧化物.利用抗拉强度测试和超声无损检测等方法对12Cr-ODS铁素体钢的力学性能进行了分析.      

硬质合金与球墨铸铁热等静压扩散连接的研究

用热等静压扩散连接法获得了硬质合金与球墨铸铁的直接连接接头和以镍箔为中间夹层的间接连接接头。采用金相、扫描电镜、显微硬度及电子探针显微分析等手段对结合界面区域的组织结构、显微硬度变化及元素扩散进行了研究。对直接连接和间接连接接头的接合强度进行了评估,并对接头断裂特性进行了分析。