Steel/CFRP复层材料构件的混合热共冲工艺研究

为了满足新能源车辆对轻量化及高强度的严苛要求,提出将高强度钢板与CFRP预浸料组成Steel/CFRP复层材料,通过两种异质材料的匹配设计和优势互补,实现车体承力件轻量化新思路。针对Steel/CFRP,提出适用于轻量化Steel/CFRP车体构件高效量产的混合热共冲工艺,阐述了其工艺原理及特点;设计开发了用于Steel/CFRP复层材料盒形件混合热共冲成形工艺试验用的可加热温控模具,介绍了其结构组成及主要零件。开展了相应的工艺试验,证明了所提出Steel/CFRP复层材料构件混合热共冲工艺方案的可行性和有效性,为后续对Steel/CFRP构件混合热共冲过程中材料的成形性能、变形行为、界面结合状态及安全性、吸能性研究,提供了必需的实验样品。     

搅拌摩擦点焊下压量对界面畸变的影响

通过采用针对同种铝合金点焊接头界面的铜箔示踪方法,对2 mm厚6061-T6铝板进行搅拌摩擦点焊工艺优化试验,设定点焊界面畸变几何特征参量,重点研究在不同轴肩下压量的条件下,接头界面畸变形貌特征的演变规律及其对接头力学性能的影响.结果表明,相较于其它焊接工艺变量而言,搅拌头轴肩下压量的变化对接头界面畸变形貌的影响最为明显;增加轴肩下压量可基本消除点焊接头界面翘曲,并能够拓宽有效连接区域,提高接头抗剪切性能.     

AZ31B/TC4填镍夹层激光-电弧对接熔化焊特性

为探求高界面反应温度下AZ31B/TC4异种合金的焊接冶金行为,开展了对1.5 mm厚AZ31B镁合金和1.0 mm厚TC4钛合金板材的对接焊研究。试验采用激光-TIG电弧双面焊焊接工艺,通过控制TIG焊电弧的偏移距离,调控激光与电弧复合热源的能量分布,获得更满意的焊缝成形;通过填镍夹层,改善界面润湿和结合能力。采用扫描电镜、金相显微镜、万能拉伸试验机分析了接头宏微观组织形貌和拉伸性能。研究结果表明:采用激光-TIG电弧双面焊接工艺,能够获得连续、美观、稳定的焊接接头成形,焊接接头的抗拉强度为153.7 MPa;焊接接头横截面呈"楔形"结合形貌,Mg/Ti界面实现熔化焊,钛合金镶嵌在镁合金中间,得到了冶金连接接头;镁/钛界面结合良好,没有裂纹、气孔等缺陷,镁合金铺展在熔化的"楔形"钛合金表面,增大了镁/钛界面的连接面积,进而提高了镁/钛界面的承载能力。     

激光毛化对铝/钢电弧熔钎焊接头界面与性能的影响

使用高性能铝/钢焊接件是汽车轻量化一直追求的目标. 针对铝/钢接头界面脆性金属间化合物层导致接头性能较差并限制其应用的问题,采用小功率激光毛化处理工艺改变钢表面微观形貌,开展铝上钢下的TIG熔钎焊试验. 通过扫描电镜观察分析了接头界面金属间化合物层的形态与分布,研究了激光毛化线间距对液态铝在钢表面润湿铺展行为及接头钎接界面金属间化合物形态与分布对接头力学性能的影响规律. 结果表明,钢表面经毛化处理后,液态铝在其表面的润湿铺展性能变差,但接头钢侧界面由平直状态变为凹槽锯齿状弯曲状态,使铝钢反应接触面积增大、机械咬合作用增强,同时凹槽对裂纹的扩展起到阻断作用,提高了接头的力学性能. 金属间化合物分布呈现出由沿界面均匀连续性分布变为凹槽内数量较多的非均匀分布特征. 当线间距为130 μm时,接头平均抗拉剪强度达到85.8 MPa.     

树脂基CFRP/金属异种材料激光连接工艺研究现状

树脂基碳纤维增强复合材料(CFRP)作为新型轻质结构复合材料,广泛应用于航空航天器件的零部件中。CFRP与航空常用金属传统连接主要有胶接和机械连接,但具有一定的局限性。激光连接技术具有能量密度高,可控性好等特点,可用于复合材料和金属的连接。本文针对当前树脂基CFRP与金属(铝合金、钛合金、钢等)激光连接接头成形机理以及接头缺陷进行了综述,同时分析了焊接工艺、组织结构优化以及焊前金属表面处理对接头成形的调控,并对CFRP/金属激光连接的发展趋势提出了展望。     

CFRP/金属异种材料激光连接工艺的研究现状

树脂基碳纤维增强复合材料（CFRP）作为新型轻质结构复合材料,广泛应用于航空航天器件的零部件中。CFRP与航空常用金属传统连接主要有胶接和机械连接,但具有一定的局限性。激光连接技术具有能量密度高,可控性好等特点,可用于复合材料和金属的连接。本文针对当前树脂基CFRP与金属（铝合金、钛合金、钢等）激光连接接头成形机理以及接头缺陷进行了综述,同时分析了焊接工艺、组织结构优化以及焊前金属表面处理对接头成形的调控,并对CFRP/金属激光连接的发展趋势提出了展望。     

TiAlNbV/TC4扩散连接接头界面组织及力学性能研究

对TiAlNbV和TC4合金进行扩散连接试验,并对其焊接接头进行了界面扩散分析和剪切性能测试,研究了接头的剪切断面形貌。结果表明:随着保温时间的增加,TiAlNbV/TC4焊接接头扩散界面区域的孔洞和黑线缺陷减少,元素的分布均匀性提高,焊接接头的最大剪切力和剪切强度增大,剪切断面形貌由凹坑过渡到韧窝,断裂类型由脆性过渡到韧性。扩散温度为850℃,保温时间为2 h时,焊接接头整体扩散结合质量较高,表现出很好的元素扩散效果,剪切强度达到最大,为166 MPa。     

T91/12Cr2MoWVTiB异种钢管TLP接头组织及断口形貌

用FeNiCrSiB非晶合金箔作中间层,在大气环境下用氩气保护,采用瞬时液相扩散焊(TLP)双温工艺和传统的TLP工艺对T91/12Cr2MoWVTiB异种钢管进行连接,测试了常温下接头的力学性能,用扫描电镜分析了其弯曲断口形貌及接头界面的显微特征。结果表明,T91/12Cr2MoWVTiB异种钢TLP双温工艺有利于提高接头组织性能,形成的界面模糊,起始断裂区形貌为韧窝,扩展区断口为解理断裂,没有明显的二次裂纹。     

基于数值模拟和响应面法的无铆钉滚压连接接头静强度研究

以2 mm厚的1060铝合金板材为研究对象,利用有限元分析软件ABAQUS建立无铆钉滚压连接有限元模型,并通过仿真得到成形接头的几何形貌及其受拉剪作用下的静强度.将接头成形过程中的凹模深度、 凸模外圆角和凸模内圆角作为影响因素,以接头静强度为优化目标,采用响应曲面分析法对板材无铆钉滚压连接各影响因素进行优化.从结果中分...     

钴/镍复合中间层真空扩散连接钨与钢

以钴粉/镍箔为复合中间层,采用800,900和1 000 ℃等三种连接温度,加压10 MPa并保温120 min的工艺条件,对钨/钢真空扩散连接. 研究了接头的微观组织、成分分布、力学性能及断口特征. 结果表明,连接温度为800 ℃和900 ℃时,钨/中间层界面金属间化合物生成很少,对应接头抗剪强度分别为186 MPa和172 MPa,断口均位于钨母材中近界面的位置,为典型解理断裂形貌;当连接温度升至1 000 ℃时,钨/中间层界面生成厚度小于2 μm的连续金属间化合物层,接头抗剪强度降至115 MPa,断裂也发生在钨母材中近界面的位置,断口大部分区域为沿晶断裂特征.     

Refill Friction Stir Spot Welding of Similar and Dissimilar Alloys:A Review

Refi ll friction stir spot welding, also known as friction spot welding(FSpW), is a solid-state welding process suitable for spot joining of lightweight materials. Through the eff orts of improving joint quality for similar and dissimilar materials, for example, aluminum and magnesium, this joining technology is well developed. The joining mechanism and process characteristics of FSpW have been widely studied. However, the application of FSpW in industry has not been entirely successful. In this review article, the research of similar and dissimilar material joints, such as, Al/Cu, Al/Ti, Al/Mg and Al/Steel, is summarized. The microstructural features and mechanical properties of the joints, welding tool and the application development are discussed in detail.     

Microstructure and Mechanical Properties of Cold Metal Transfer Welding Similar and Dissimilar Aluminum Alloys

Integrating structures made from aluminum alloys in automotive industry requires a large amount of joining. As a consequence, the properties of the joints have a significant influence on the overall performance of the whole structure.Robot cold metal transfer welding is a relatively new joining technique and has been used in this work to join 6082-T4 and5182-O aluminum alloy sheets by using ER5356 and ER4043 filler metals. Microstructure characterization was performed by optical microscopy and energy dispersive X-ray spectroscopy, and the mechanical properties were measured by tensile and hardness tests. A correlation is made between welding variables, mechanical properties and the microstructure of welded joints. Results indicate that robot cold metal transfer welding provides good joint efficiency with high welding speed, good tensile strength, and ductility. Owing to the low heat input of robot cold metal transfer welding process, the heat affected zone microstructure was quite similar to base metals, and weld metal microstructure was the controlling factor of joint efficiency. The best performing were the 5182/5182 joints welded with ER5356 and these had mechanical property coefficients of 100%, 98%, and 85% for yield strength, ultimate tensile strength, and elongation, respectively.     

Mechanisms of joining aluminium A6061-T6 and titanium Ti–6Al–4V alloys by cold metal transfer technology

Abstract

Cold metal transfer (CMT) welding–brazing joining of Ti6Al4V and Al A6061-T6 was carried out using AlSi₅ wire. The joining mechanisms and mechanical properties of the joints were identified and characterised by scanning electron microscope, energy dispersive spectroscopy and tensile–shear tests. Desired CMT joints with satisfied weld appearances and mechanical properties were achieved by overlapping Ti on the top of Al. The joints had dual characteristics of a welding joint on the aluminium side and a brazing joint on the titanium side. Three brazing interfaces were formed for the joint, which increased the strength of the joint. An intermetallic compound layer was formed at the brazing interface, which included Ti₃Al, TiAl and TiAl₃. Two different fracture modes were also observed: one fractured at the welding/brazing interface and weld metal and the other at the Al heat affected zone (HAZ). Clearly, the joints fractured at the Al HAZ had higher tensile strength than those fractured at the welding/brazing interface and weld metal.     

Hybrid joining process for carbon fiber reinforced thermosetting plastic and metallic thin sheets by chemical bonding and plastic deformation

A new joining process for thin metallic and continuous carbon fiber reinforced thermosetting plastic (CFRP) sheets is proposed. This joining process is a hybrid of chemical bonding and plastic deformation, usable for ultra-lightweight structures. In contrast to conventional joining methods, such as rivet joining with an adhesive, the proposed method does not require any additional components and can eliminate holes that would cut the continuous carbon fibers and cause stress concentration. Hence, a smaller weight and a higher joining quality can be attained, especially for thin sheets. Aiming at making comparison and demonstrating the applicability of the proposed hybrid joining method, two thermosetting CFRP sheets with different laminates were used as lap adherends in the experiment. The effects of the deformation temperature, the use of a dummy sheet and the relative positions of the sample and dummy sheet on the joining quality were systematically investigated and optimized. The optimal hybrid joint shows high-quality bonding without delamination or adhesive failure. The tensile shear test of single-lap A2017P-CFRP hybrid joints manufactured under optimal experimental conditions indicates that, compared with adhesive bonding and conventional rivet joining with an adhesive, the proposed joining method has obvious superiority in terms of tensile shear load, slip displacement and absorption energy.     

Numerical Modeling of Ti Deformation for the Development of a Titanium and Stainless Steel Transition Joint

Finite element analysis (FEA) was used to model the joining of titanium grade 2 (Ti) to AISI 321 stainless steel (SS) transition joint of lap configuration with grooves at the interface on SS side. The hot forming of Ti for filling the grooves without defects was simulated. FEA involving large plastic flow with sticking friction condition was initially validated using compression test on cylindrical specimen at 900 °C. The barreled shape and a no-deformation zone in the sample predicted by FEA matched with those of the compression experiments. For the joining process, FEA computed the distribution of strain and hydrostatic stress in Ti and the minimum ram load required for a defect-free joint. The hot forming parameters for Ti to fill the grooves without defects and any geometrical distortion of the die were found to be 0.001 s^?1 at 900 °C. Using these conditions a defect-free Ti-SS joint was experimentally produced.     

Dissimilar materials joining of metal/carbon fibre reinforced plastic by resistance spot welding

ABSTRACT

Dissimilar materials joining of metal to carbon fibre reinforced plastic (CFRP), which consisted of PA6, modified polypropylene (PP) or polyphenylene sulphide (PPS) as matrix polymer with short carbon fibre, was performed using series resistance spot welding (series-RSW). The metal plate was placed on CFRP plate as the lap joint, and electrodes of series-RSW were pressed only on the metal plate side. The metal around the electrode was heated by electrical resistance heating, and the thermoplastic near the interface was slightly melted by the heat conduction from heated metal. The objectives of this research are to confirm the possibility of direct joining of CFRP and metal, and to investigate the effects of the heat input during series-RSW, silane-coupling treatment and chemical structure of matrix plastics on the joint properties.

The direct joint formations of SUS304 to CFRP (PA6) and CFRP (PP) were accomplished, and CFRP (PPS) was not. The joining area, which corresponding to the melted area of CFRP, enlarged with increasing the welding current and welding time, therefore, the tensile shear fracture load also increased. The silane-coupling treatment for metal surface was highly effective to increase the joining strength. The maximum tensile shear strength of about 13 MPa was obtained for SUS304/CFRP (PA6) joint.     

Development of butt welding of polymeric materials based on softening and stirring effects by hot tool

In this study, new butt welding technique was proposed to join polymeric materials in which the polymeric material is softened by a heated tool due to the Joule effect heating of the electric current flow through the tool, and the coalescence of material is done by the stirring action due to the tool rotation. A 3 mm-thick Polycarbonate (PC) sheets were joined in various joining conditions, from which joining mechanism, mechanical properties of joints and process parameters affecting joint performance were investigated. In the experiments, in situ observation with a CCD camera and material temperature measurement during the process, as well as the observation of surface appearance and cross section of the joint and tensile test were performed for these purposes. It was shown from the in situ observation and material temperature measurement that the molten and softened region is formed around the weld tool. It was also shown that sufficient heat input was required to form sound joints with acceptable performance, which depended upon the joining speed and amount of electric current flow through the tool. The observation of joint appearance and cross section revealed that the joint with comparable thickness to base material was obtained under the condition of revolution pitch below 0.08 mm, defined by the ratio of joining speed to tool rotation. It is noticed that joints obtained from the proper conditions have the same mechanical properties as the base material, and that the process parameters of this method were tool rotation speed, welding speed and amount of electric current. These results suggest proposed method is useful for joining the polymeric materials.     

Design of hole-clinching process for joining of dissimilar materials – Al6061-T4 alloy with DP780 steel,hot-pressed 22MnB5 steel,and carbon fiber reinforced plastic

The mechanical joining of dissimilar materials is a key technology in the automotive industry as it enables the realization of car bodies that incorporate multiple materials. However, it remains difficult to join materials such as aluminum alloy to high-strength/low-ductility materials such as advanced high-strength steel, hot-pressed steel, and carbon fiber reinforced plastic by using joining methods that are based on forming technology. The purpose of this study is to develop a new joining process, called “hole clinching,” for these material combinations. In the hole-clinching process, the ductile material is positioned uppermost and the brittle material—into which a hole is formed—is positioned below that. The upper sheet is indented into a die cavity through the hole in the lower sheet and spread so that the two sheets interlock geometrically. In this study, hole-clinching tools were designed based on the geometrical relationship between the forming volume and the joint strength. Finite element analysis and practical experiments were performed to verify the practicality of the hole-clinching process. The cross-sections of the hole-clinched joints formed in our experiments were in good agreement with the results of the finite element analysis. Then, a single-lap shear test was performed to evaluate the joint strength. The hole-clinched joints, regardless of the material combinations, provided a joint strength in excess of the desired 2.5 kN. These results point to the applicability of the hole-clinching process to the joining of dissimilar materials.     

Simulation of Tensile Behavior in Friction Stir Welded and Superplastically Formed-Titanium 6Al-4V alloy

A hybrid numerical and experimental study was undertaken to evaluate the performance of friction stir welded (FSW) and superplastically formed friction stir welded (SPF-FSW) titanium joints. This paper presents the numerical models which were developed to simulate mechanical response of FSW and SPF-FSW joints. The simulation results were compared to experimentally determined behavior characteristics of the joints to assess the validity of the modeling approach. It was found that numerical modeling have simulated successfully the tensile behavior of a FSW joint agreeing with the experimental results. This method also adequately simulated the tensile behavior of a SPF-FSW joint, but due to geometrical influences, there are discrepancies between the numerical results and experimental observations.     

反应连接碳化硅材料接头的力学和电性能

采用反应连接的方法实现了反应烧结碳化硅(RB—SiC)之间以及反应烧结碳化硅和重结晶碳化硅(R-SiC)之间的连接。分别在光学显微镜、扫描电镜上观察了连接区的显微组织和断口形貌，并用弯曲强度和电阻率评价了反应粘接硅／碳化硅材料接头的机械和电性能。研究结果表明，反应连接可以使母材间形成良好的接合界面，连接层未对整体材料的强度和电阻率造成明显的影响。接合区组织和成分的优化是获得碳化硅材料优异连接性能的关键。