FSW对2A12铝合金时效成形的影响

为评价2A12铝合金FSW构件的时效成形工艺,研究了FSW对2A12铝合金时效成形的影响,设计了以时间为参数变量的带焊缝与不带焊缝时效成形工艺的对比试验,并进行FSW焊件与非焊件时效成形力学性能对比研究及成形性分析。结果表明,在其他条件相同的情况下,非焊接试样时效成形时,最佳回弹时效时间为10h,回弹率达25.41%;FSW焊件时效成形时,最佳回弹时效时间为8h,回弹率达33.49%。非焊接试样时效时间8h,抗拉强度达到463.4MPa;FSW试样时效时间8h时,抗拉强度达到354.1MPa。经时效成形处理的非焊接试样和FSW试样的强度均有提高,且非焊接试样的硬度明显高于焊接试样。FSW工艺对时效成形试样的回弹、力学性能及表面硬度均产生了不同程度的负面影响。     

Effects on the Surface Texture,Superplastic Forming,and Fatigue Performance of Titanium 6AL-4V Friction Stir Welds

The speed and feed effects of the friction stir welding (FSW) process on the surface texture along the top of a butt welded nugget were studied. The tests were conducted using fine grain (0.8-2 μm) titanium alloy 6Al-4V with a nominal thickness of 2.5 mm. It was shown that the pin tool marks along the top surface of the weld can be highly detrimental to both the superplastic forming (SPF) characteristics and the fatigue performance of welded panels. Removing the marks by machining the top surface after FSW was found to eliminate the predominant tearing of the weld during SPF and most of the fatigue life of across the weld was also restored. Through additional development of the FSW process parameters, the butt welded nugget was made to have equivalent SPF characteristics as the parent sheet material. By using a water-cooled pin tool and other cooling techniques, it is believed that the weld zone can be kept below the beta transus temperature during FSW, which enables the formation of a grain structure that is uniquely conducive to superplastic behavior, when compared to conventional fusion welding processes.     

Evaluation of joint performance of 5056 aluminium alloy friction welded joints by heat input. On the tensile strength of welded joints (1st report)

Ferritic stainless steel SUS430 sheets were friction stir welded by using a Ni-base dual two-phase intermetallic alloy tool. After friction stir welding (FSW), the SUS430 work and the tools were evaluated in terms of microstructure and mechanical properties. The tensile specimens cut from the welded joints fractured in the base metal portion and their fracture strength was equal to that of the base metal. The stir zone comprised of recrystallized fine microstructure was observed, and also the thermo-mechanically affected zone was observed in an advanced side. Hardness in the upper one-third layer of the welded cross section was higher than the base metal. The admixture matter from work to tool surface occurred whereas that from tool to work surface did not take place in the scanning electron microscopy-EPMA resolution level. The amount of wear of tool was negligibly small, suggesting that the Ni-base dual two-phase intermetallic alloy is promising as a new type of FSW tool used for high melting materials such as steel.     

钛合金搅拌摩擦焊接最新研究进展

钛合金具有密度低、比强度高,耐蚀性好,加工性能优异等优点,主要应用于航空航天、交通运输和石油化工等领域。当钛合金作为结构材料应用在不同领域时,传统的熔融焊接方法会产生较大残余应力,组织粗化,变形大,裂纹和孔隙等缺陷;而采用搅拌摩擦焊接技术可以避免传统熔融焊接方法产生的缺陷,从而大幅度提高钛合金焊接接头质量。目前,钛合金的搅拌摩擦焊接技术已成为国内外研究热点。主要介绍搅拌摩擦焊接的原理、工艺特点,国内外关于钛合金FSW焊接接头的宏观形貌、微观组织(晶粒大小、织构)和力学性能等方面的最新研究进展,最后展望了钛合金FSW未来的研究方向。     

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.     

强制冷却对TC4钛合金搅拌摩擦焊接接头组织性能影响

分别在空气和强制冷却条件下对TC4钛合金板进行了搅拌摩擦焊接(Friction stir welding,FSW),对比研究了焊接接头的微观组织和力学性能。结果表明,FSW接头分为搅拌区、热机械影响区和母材区。母材区为热轧退火后的初生α和β双相组织。空气条件下焊接,搅拌区为α+β片层结构,组织转变主要为β相转变为片层α+β两相,热机械影响区为等轴晶α和α+β片层的双态组织,组织转变受动态再结晶和相变共同作用。强制冷却条件下焊接,搅拌区为针状马氏体,组织转变主要为马氏体相变。与空气条件下接头相比,强制冷却条件下的FSW接头显微硬度明显提高,但抗拉强度略微降低。     

Comparative study on fatigue properties of friction stir and MIG-pulse welded joints in 5083 Al-Mg alloy

The objective of this investigation was to compare the fatigue properties of friction stir welds with those of MIG-pulse welds. The 5083 Al-Mg alloy was welded by single pass friction stir welding（FSW） and double-sided MIG-pulse welding. The results show that friction stir（FS） welds have a better appearance than MIG-pulse welds for the lack of voids, cracks and distortions. Compared with the parent plate, FSW welds exhibit similar fine grains, while MIG-pulse welds display a different cast microstructure due to the high heat input and the addition of welding wire. The S-N curves of FSW and MIG-pulse joints show that the fatigue life of FS welds is 18 - 26 times longer than that of MIG-pulse welds under the stress ratio of 0.1 and the calculated fatigue characteristic values of each weld increase from 38.67 MPa for MIG-pulse welds to 53.59 MPa for FSW welds.     

铝合金搅拌摩擦与MIG焊接接头疲劳性能对比试验

根据疲劳S-N曲线试验结果,对5A06铝合金搅拌摩擦焊(FSW)和MIG焊接接头的疲劳性能进行了初步比较,分析讨论了搅拌摩擦焊过程中所产生的焊接缺陷对其疲劳性能的影响.结果表明,在焊态下由于焊接接头几何形状等的影响,FSW的疲劳强度明显高于MIG焊接接头;对FSW焊缝根部的"吻接"缺陷(kissing-bonds)是降低FSW焊接接头疲劳寿命的主要因素,旋转搅拌工具在焊缝表面形成的多余飞边将对疲劳行为产生明显影响.     

Evaluation of corrosion and wear resistance of friction stir welded ZK60 alloy

Owing to the low corrosion and wear resistance of magnesium alloy, surface properties are the key factors affecting its application. But few studies have concentrated on the surface properties of friction stir welded Mg–Zn–Zr alloy. The aim of the present paper is to investigate the effects of friction stir welding (FSW) and subsequent ageing on the surface corrosion and wear resistance of ZK60 alloy. It is found that due to the significant grain refinement and redistribution of precipitates, the surface corrosion and wear resistance of ZK60 plates are enhanced by FSW. Morphology of inter-granular corrosion in base metal is changed into pitting corrosion after welding. Subsequent ageing can significantly reduce the corrosion resistance of the welded plates.     

搅拌摩擦焊AA7075-T651铝合金接头的疲劳裂纹扩展(英文)

研究12 mm厚AA7075-T651铝合金板搅拌摩擦焊接头的疲劳裂纹扩展行为。从搅拌摩擦焊接头以及母材中截取试样,对试样进行疲劳裂纹扩展实验。对搅拌摩擦焊接头以及母材的横向拉伸性能进行评估。用光学显微镜和透射电镜分析焊接接头的显微组织。用扫描电镜观察试样的断裂表面。与母材相比,焊接接头的ΔKcr降低了10×10-3 MPa·m1/2。搅拌摩擦焊AA7075-T651接头的疲劳寿命明显低于母材的,其原因可归结于焊缝区的析出相在搅拌摩擦焊接过程中的溶解。     

Improvement of the drawability based on the surface friction stir process of AA5052-H32 automotive sheets

Based on the imperative social demand for lighter vehicles, lightweight materials such as aluminum alloys are expected to replace conventional steels in many automotive applications. In automotive parts manufacturing, most of the components produced in conventional stamping operations are geometrically complex as the blanks are subjected to both stretching and drawing deformations. However, aluminum alloys have intrinsic drawbacks, such as the inferior formability of these materials, although the effects of the weight reduction in terms of performance are highly promising. In an effort to improve the formability of aluminum alloy sheets, the surface friction stir process is proposed in this study. This process locally modifies the surface of automotive aluminum alloy sheets via stirring and advancing on the surface of the sheet, similar to the Friction Stir Welding (FSW) process that utilizes a probe without a pin. When the surface of the sheet is modified locally by stirring, dynamic recrystallization due to the severe shear deformation along with heat resulting from the friction occur due to changes in the micro-structure and mechanical properties in the stirred zone, while the dislocation density and grain size refinement are curtailed. In this work, the drawability performance of AA5052-H32 sheets (thickness 1.5 mm) that were welded using the surface friction stir process was experimentally and numerically investigated in cylindrical cup drawing tests. When applied to AA5052-H32 automotive sheets, the surface friction stir process improved the drawability of the entire aluminum alloy sheet. For numerical simulations, the non-quadratic anisotropic yield function Yld2000-2d was employed along with isotropic hardening, while the formability was evaluated by utilizing theoretical forming limit diagrams (FLD) based on Hill's bifurcation and M-K theories.     

Superplastically Formed Friction Stir Welded Tailored Aluminum and Titanium Blanks for Aerospace Applications

The purpose of this study was to develop a specialized friction stir welding process for superplastic grade aluminum alloy 5083-SP and titanium alloy 6Al-4V, in thickness of 1.5-4 mm, such that the butt welded nugget would have equal superplastic forming (SPF) characteristics as the parent sheet material. The concept of using tailored blanks for the SPF process is proposed which will allow the joining of multiple pieces to fabricate much larger monolithic components than has been possible in the past. Another benefit of using tailored blanks for SPF applications was found to be a more closely matched blank shape relative to the plan size of the SPF forming die. However, shape of the tailored blanks is critical in SPF of a component. An example of this might be the case where a polygon-shaped blank might work in order to reduce the amount of material used, but a rectangular blank is currently used because a tailor made blank with superplastic joints was not found to be technologically feasible. Upon development of a suitable FSW process for each material, the technology was applied to fabricate full scale test components representing a generic jet engine nacelle Lipskin.     

Friction stir welding of AZ31 magnesium alloy

Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.     

Friction stir welding of V-1461 and V-1469 high strength aluminium–lithium alloys

The problems of the technology of friction stir welding (FSW) of new high-strength aluminium–titanium alloys V-1461 and V-1469 are discussed. The technical and economical advantages of the process are shown, the parameters are determined and the optimum FSW conditions resulting in high mechanical properties of the welded joint are proposed.     

钛合金的搅拌摩擦焊探索

通过对钛合金热物理性能分析，比较了钛合金的搅拌摩擦焊特性；针对钛合金的特点特别设计和使用了可以满足钛合金搅拌摩擦焊的搅拌头、垫板、冷却和保护装置等；并且对Ti-6Al-4V钛合金的搅拌摩擦焊焊缝和接头进行了观察分析，还对接头力学性能进行了测试，初步试验结果表明搅拌摩擦焊可以实现钛合金焊接，接头强度可以达到母材强度90％以上，但是搅拌摩擦焊工艺、参数、搅拌头还需要进一步优化，性能指标还可以进一步提高。     

Evolution of Mechanisms of Plastic Strain Responsible for Structure Formation in Near-Weld Zone Under Friction Stir Welding

Metal Science and Heat Treatment - The microstructure of welded joints obtained by friction stir welding (FSW) of structural steels and aluminum, copper and titanium alloys is studied. It is shown...     

2219高强铝合金焊接接头的腐蚀性能

采用浸泡试验、极化曲线以及电化学阻抗测试,对2219高强铝合金母材和焊接接头在3.5%NaCl溶液中的腐蚀性能进行研究。浸泡后试样的显微形貌表明,试样中铜元素的分布及存在形态与其腐蚀性能密切相关;极化曲线表明,在电化学腐蚀过程中,搅拌摩擦焊接头的腐蚀电流最小,电子束焊接接头次之,而钨极氩弧焊接头的腐蚀电流最大;电化学阻抗测试表明,腐蚀过程中体系阻抗值由大到小顺序为搅拌摩擦焊的接头,电子束焊的接头,母材,钨极氩弧焊的接头。     

铝合金搅拌摩擦焊接接头腐蚀行为研究进展

介绍了铝合金搅拌摩擦焊接接头腐蚀行为的最新研究进展,重点讨论了铝合金搅拌摩擦焊接接头腐蚀行为的研究方法,包括应力腐蚀法、盐雾实验法、溶液浸泡法、电化学法、凝胶可视化法等,并指出其存在的问题,分析了接头腐蚀机理及提高接头耐蚀性的方法。     

Al-Mg-Mn-Sc-Zr合金板材搅拌摩擦焊和氩弧焊焊接接头的对比

研究Al-Mg-Mn-Sc-Zr合金的焊接工艺和焊接接头组织和性能。采用搅拌摩擦焊（FSW）和氩弧焊（TIG）2种焊接工艺对该合金的热轧和冷轧-退火2种使用态板材进行焊接。采用比较研究的方法测定和研究焊接接头的力学性能和显微组织,利用光学显微镜和透射电子显微镜研究焊缝的显微组织和力学性能之间的关系。结果表明,与基材相比,Al-Mg-Mn-Sc-Zr合金的热轧和冷轧-退火板材的FSW和TIG焊接接头的强度均下降,但FSW焊接系数高于TIG焊接系数。这是因为FSW焊接接头焊核区亚结构强化的丧失和Al3（Sc,Zr）的析出强化作用的极少量丧失,而TIG焊焊接接头的软化主要原因是其形变强化的完全丧失和Al3（Sc,Zr）的析出强化作用的大部分丧失,且搅拌摩擦焊焊核区晶粒比TIG焊的焊缝区晶粒更细小。     

Establishing empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints

AA 6061-T6 aluminium alloy(Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance.Compared with the fusion welding processes that are routinely used for joining structural aluminium alloys,friction stir welding(FSW) process is an emerging solid state joining process in which the material welded does not melt and recast.Joint strength is influenced by the grain size and tensile strength of the weld nugget region.Hence,an attempt was made to develop empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints.The empirical relationships are developed by response surface methodology(RSM) incorporating FSW tool and process parameters.A linear regression relationship was also established between grain size and tensile strength of the weld nugget of FSW joints.