铝合金搅拌摩擦焊研究现状

搅拌摩擦焊具有熔化焊接无法比拟的优点,因此铝合金搅拌摩擦焊引起国内外学者的广泛关注。本文主要介绍了搅拌摩擦焊的工作原理和接头性能影响因素,详细介绍了国内外铝合金搅拌摩擦焊接头微观组织、接头力学性能和塑性流动机理以及搅拌摩擦焊焊接缺陷修补技术,指出了在塑型金属流动方面存在的不足,还需要进一步研究焊接接头质量的评定方法和搅拌摩擦焊接头缺陷的修补技术。     

搅拌摩擦焊塑性金属流动行为研究

通过观测铝合金焊缝接头显微组织形貌与塑性金属组织的流线形,并结合对搅拌过程中搅拌针周围塑性金属的受力情况分析,初步构建了搅拌摩擦焊塑性金属流动行为模型,揭示了焊接缺陷的产生原因和性能薄弱区域。研究结果表明,水平方向上将塑性金属的流动迁移过程包括5个同时进行的过程,其中前进侧切削金属较少,在后退侧,搅拌针焊接前进方向和旋转方向相反,切削金属量达到最大值。厚度方向上由于轴肩的顶锻作用,上部塑性金属向下迁移,在焊缝中部堆积形成洋葱环。实际流动过程是水平和厚度方向流动行为的叠加。     

焊后热处理对2219-T6铝合金搅拌摩擦焊接头力学性能的影响

采用搅拌摩擦焊方法对2219-T6铝合金进行焊接,对焊接接头的宏观形貌、显微组织、拉伸强度、显微硬度进行了分析。结果表明,焊核区组织为细小的晶粒,热机影响区组织为弯曲变形的晶粒,热影响区组织出现了明显粗化。接头室温拉伸强度可以达到母材的75%左右,接头强度低于母材的原因主要归结为金属的塑性损伤、缺陷的产生和热影响区的软化。通过固溶及时效方法并兼顾再结晶过程的热处理工艺可以回复接头塑性、消除软化,达到改善接头性能的目的。     

铝合金FSW拼焊板塑性变形规律研究

铝合金搅拌摩擦焊拼焊板焊缝各区力学性能的差异导致拼焊板成形时严重的不均匀性,降低了拼焊板的成形性能,极大地限制了铝合金拼焊板的应用。以2024铝合金搅拌摩擦焊拼焊板为研究对象,通过实验和有限元模拟系统研究接头力学性能失配对铝合金拼焊板塑性成形性能的影响规律和机理。对铝合金搅拌摩擦焊接头进行金相检验和硬度测试,根据接头组织及硬度分布特征,将搅拌摩擦焊接头划分为焊核区、热机影响区、热影响区以及母材区4个部分,以此建立搅拌摩擦焊接头的有限元模型,并对接头变形过程中的约束与协调变形规律进行分析。接头变形时拉伸应力在屈服应力最小的区域最低,在屈服应力较大的区域相应升高,且在接头中存在失配比交界处都会发生突变。从形变能的角度分析,这主要是由于力学性能失配而导致变形不协调及相互约束,表现在接头拉伸性能上就是屈服强度及屈服位置、抗拉强度、延伸率随接头各区失配比组合的差异。     

铝合金LD10的搅拌摩擦焊组织及性能分析

搅拌摩擦焊是 2 0世纪 90年代发展起来的新型固态塑性连接方法 ,在航空航天结构中铝合金件的焊接方面有很好的应用前景。文中试验研究了航空航天结构件常用的LD10铝合金的搅拌摩擦焊技术。通过工艺试验 ,对其塑性连接时的焊缝成形、焊缝组织形态及接头的力学性能进行了分析。研究结果表明 ,用搅拌摩擦焊方法焊接板厚6mm的LD10铝合金 ,当规范参数合适时 ,可获得外观成形美观、内部无缺陷、几乎无变形的平板对接接头。从显微组织角度 ,焊接接头可分为五个区域 ,即焊核、热力影响区、热影响区、轴肩变形区和探针挤压区 ,各区域的组织有明显的特征。接头的力学性能试验表明 ,接头的抗拉强度可达母材的 87% ,高于熔焊接头的强度 ,断裂位置大多位于热影响区     

先进的搅拌摩擦焊

搅拌摩擦焊是利用一种特殊形式的搅拌头边旋转边前进，通过搅拌头与工件的摩擦产生热量，摩擦热使该部位金属处于热塑性状态，并在搅拌头的压力作用下从其前端向后部塑性流动，从而使待焊件压焊为一个整体。它可以焊接所有牌号的铝合金以及用熔焊方法难以焊接的材料，并突破了普通摩擦焊对轴类零件的限制。由于搅拌摩擦焊是固态焊接，所以没有熔化焊时的气孔、裂纹等缺陷。搅拌摩擦焊的接头性能普遍优于熔化焊的。     

铝-铜的搅拌摩擦焊研究

搅拌摩擦焊是一种新型的固相连接方法.在铝一铜等异种材料连接方面具有潜在的应用前景.从焊接工艺、接头性能与微观组织等方面,介绍了铝一铜搅拌摩擦焊的研究进展,为进行相关技术研究提供了参考依据.分析表明.铝-铜搅拌摩擦焊的工艺参数范嗣较窄,接头力学性能有待提高;铝、铜流动特性差异的存在,导致焊核两侧呈现不同的结构;接头中存在多种金属间化合物,其分布形态、尺寸和数量对接头性能有较大影响.     

LF21超声搅拌摩擦焊接头组织及性能分析

利用超声波对金属塑性成形作用对LF21铝合金进行了超声搅拌摩擦焊接试验,并对常规搅拌摩擦焊与超声搅拌摩擦焊接头的微观组织、断口形貌进行了对比分析.结果表明,超声能量通过搅拌头有效地导入焊缝底部,在增加焊缝底部搅拌强度的同时,提高了搅拌针周围金属原子的运动和扩散能力,焊核区的金属组织有明显的晶粒细化和组织均匀化.超声搅拌摩擦焊断口韧窝数量与深度均不及常规搅拌摩擦焊,撕裂棱不明显;超声搅拌摩擦焊可以提高接头力学性能,但平均断后伸长率相比常规搅拌摩擦焊有所下降.     

火箭贮箱箱底龙门铣焊装备静力学特性分析

结合目前世界上最大的10 m级大直径运载火箭贮箱箱底搅拌摩擦焊接工艺需求,设计了用于大直径球面体搅拌摩擦焊的龙门式焊接装备。由于搅拌摩擦焊是通过被焊材料与高速旋转的焊接头进行摩擦产生热量并使其产生局部塑性化,当焊具沿着焊接界面向前产生位移时,塑性化的材料在焊接头处转动摩擦力的作用下由焊具的前部向后部流动,并在焊接头挤压下形成致密的固相焊缝。与熔焊不同的是,搅拌摩擦焊过程中需要焊接装备提供较大而且非常稳定的顶锻力和搅拌力,因此,龙门铣焊装备整体结构的力学特性分析非常重要。首先结合厚度为28 mm的铝合金材料2219在搅拌摩擦焊过程所需的作用力以及火箭贮箱箱底球面结构,建立焊接头的焊接过程力学方程,进而分析焊接过程中龙门铣焊装备的静力学特性。结果表明：所设计的龙门铣焊装备在焊接头扎入阶段、稳定焊接阶段的最大应力以及U形头最大变形量均与搅拌头和箱底夹角存在线性关系,而且从强度角度来说,目前设计的龙门式装备具有裕度过大的不足,可以改进。     

2024-T4铝合金超声辅助搅拌摩擦焊接头组织与性能研究

沿搅拌头方向将超声能量引入对接焊焊缝,利用超声波的振动作用,促进搅拌针周围金属原子的运动和扩散能力,能有效地细化和均匀化焊核区的金属组织,改善焊缝材料的塑性流变行为,增强焊缝底部的搅拌强度,提高搅拌摩擦焊焊接质量和焊接效率。通过对1.8 mm厚2024-T4铝合金进行平板对接焊试验,对比研究了搅拌摩擦焊焊接接头组织与性能。结果表明,超声辅助搅拌摩擦焊能有效减少焊接缺陷,并且接头强度提高了10%,超声辅助搅拌摩擦焊优越性效果明显。     

5052铝合金FSW接头组织和力学性能

采用搅拌摩擦焊焊接8 mm厚5052-O铝合金,并对焊接接头进行了显微组织观察和力学性能测试。结果表明:接头组织左右不对称,前进侧与母材分界线较明显,后退侧与母材分界线较模糊;焊接接头抗拉强度平均值为193.5 MPa,接头强度可达母材的99%,伸长率可达母材的84%;焊接接头正弯角和背弯角均可达到180°,弯曲性能良好;焊核区显微硬度约为72 HV,略高于母材,硬度最低点出现在前进侧熔合过渡区。     

Microstructure and Properties of TIG/FSW Welded Joints of a New Al-Zn-Mg-Sc-Zr Alloy

A new Al-Zn-Mg-Sc-Zr alloy with low Sc content was welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques. The microstructure and properties of those two welded joints were investigated by property tests and microstructural observations. The results show that the new Al-Zn-Mg-Sc-Zr alloy has desirable welding property. The ultimate tensile strength and welding coefficient of the TIG joint reach 405 MPa and 76.7%, respectively, and in FSW joint those property values reach 490 MPa and 92.6%, respectively. The studied base metal has a deformed fibrous subgrains structure, many nano-scaled Al₃(Sc,Zr) particles, and very fine aging precipitates. In the TIG joint, the fusion zone consists of coarsened dendritic grains and the heat-affected zone (HAZ) has fibrous micro-scaled subgrains. The FSW welded joint is characterized by a weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. Due to plastic deformation around the rotating pin and anti-recrystallized effectiveness of Al₃(Sc,Zr) particles, the weld nugget zone has a very fine subgrain structure. The TMAZ experiences some dissolution of aging precipitates. Coarsening of aging precipitates was observed in the HAZ. The better mechanical properties of the FSW joint are derived from a fine subgrain structure and homogeneous chemical compositions.     

2219-O铝合金的搅拌摩擦焊接

对2219-O铝合金进行了搅拌摩擦焊接,采用光学显微镜分析了接头的微观组织,采用拉伸试验方法评价了接头的力学性能.微观分析表明,在热机循环的共同作用下,焊核区(WNZ)发生了动态再结晶,形成了细小的等轴晶粒,并且沉淀相的数量较其它各区有所增加;热机影响区(TMAZ)晶粒被拉长、弯曲,发生了动态回复和部分再结晶,晶粒内部开始有新的晶粒生成;热影响区(HAZ)的晶粒发生粗化.力学性能测试结果表明,当转速为800r/min,焊接速度为200～400 mm/min时,接头与母材等强度,断裂发生在母材区;当焊接速度大于400mm/min时,接头的抗拉强度很低,断裂发生在缺陷处.     

Tensile properties and failure analysis of Ti–6Al–4V joints by electron beam welding

The microstructural and mechanical characterization of electron beam welded joints of forged Ti–6Al–4V were investigated. Microhardness tests indicate that the hardness of the fusion zone(FZ) is higher than that of the heat-affected zone(HAZ) and base metal. The tensile results show that the mechanical properties of the welded joints are comparable with those of the base metal in terms of static strength and are in accordance with the relationship between microstructure and mechanical properties of welded joints. The ultimate tensile strength of the weld is equal to that of the hourglass joint, which indicates that the mechanical properties of the longitudinal FZ and those of the transverse FZ are the same. Macromechanical behavior and macrofracture and microfracture of the base material,joint, and weld specimens are observed. A comparison among the three types of specimen fracture phenomena reveals the following distinctive differences:(1) the fracture mode,(2) the micrograph of the dimple pattern at the central region, and(3) the size of the dimple at the central region and the transition region.     

厚板AZ31镁合金搅拌摩擦焊焊接接头的组织与性能

对10mm厚板A231镁合金成功进行了搅拌摩擦焊接,获得成形良好、表面光滑、无裂纹、无气孔的焊接接头.研究该搅拌摩擦焊接头不同区域的显微组织特征,并通过拉伸、冲击和硬度试验分析了焊接接头的力学性能.结果表明,焊缝中心区是均匀细小的等轴晶粒,热力影响区晶粒大小不均匀,存在较明显的塑性流变带结构;焊接接头的抗拉强度达到母材的80%以上,焊接接头的冲击韧性比母材高,焊接接头的显微硬度比母材稍有降低,焊接接头具有较好的力学性能,说明搅拌摩擦焊是焊接厚板镁合金的一种有效方法.     

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.     

Mechanical properties and microstructures of resistance spot welded DP980 steel joints using pulsed current pattern

Dual phase 980 MPa grade (DP980) steel sheets were resistance spot welded using a pulsed current, and the effects of the pulsed current on the strength properties of the joints were investigated. The pulsed current improved the mechanical properties of the joints in cross tensile tests. In situ observations during tear tests revealed that the ductility of the nugget was improved and that the propagation of cracks into the nugget was inhibited when the pulsed current was used. Microstructural observations and electron probe microanalysis (EPMA) of the nugget showed that the segregation of phosphorus at the nugget was reduced in the joint welded using the pulsed current, suggesting that the pulsed current improved the ductility of the nugget by altering their microstructures.     

高强镁合金点焊接头性能

采用电阻点焊方法对高强镁合金Mg₉₆Zn₂Y₂进行了焊接.通过扫描电子显微镜对接头微观组织进行了观察,分析了接头的组织,研究了焊接电流对接头熔核直径及抗剪载荷的影响.在此基础上探讨了接头组织对接头性能的影响.结果表明,接头熔核直径与抗剪载荷均随焊接电流的增大而增大,接头最大抗剪强度约为142 MPa;接头熔核区第二相呈细网状分布,其α-Mg晶粒发生了粗化,直径约为30 μm.熔核区这些组织特征被认为是接头弱化的主要原因.     

Microstructures and mechanical properties of friction stir welded joints of Zr–Ti alloy

Zirconium–titanium alloy joints were successfully produced by friction stir welding. Unlike the (α+β) dual phase microstructure in base metal, only the β phase existed in the region in which temperature exceeded the β transient point for the as welded joint. Accordingly, the hardness in these regions exhibited integral decrement and uniform distribution features. The thermal simulation further showed that hardness variation was mainly determined by phase composition. Microstructure development in the nugget zone was mainly governed by continuous dynamic recrystallisation. Satisfactory ultimate tensile strength and elongation equal to the base metal were achieved in the as welded joint. Tensile fracture occurred at the heat affected zone near the retreating side of the joint. The fracture surface of the joint exhibited a mixing feature with quasi-cleavage facets and small dimples.