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     

7050-T7451铝合金搅拌摩擦焊组织及性能分析

在不同的焊接工艺参数下对8mm厚的7050-T7451锚合金板进行 了搅拌摩擦焊接实验通过对焊接接头组织的分析,发现焊核区晶粒为明显的细化再结晶等轴晶;热机影响区晶粒沿流线方向拉长且有细小沉淀相在晶界上析出;热影响区的组织发生了晶粒粗化.沿焊缝横截面的显微硬度分布呈高-低-高-低-高的趋势,硬度最低处位于后退侧的热影响区.实验结果表明,在旋转速度为375r/min、焊接速度为100mm/min时,可以获得较好的焊缝组织织,抗拉强度达到了 452MPa.     

LY12铝合金搅拌摩擦焊接头组织和性能研究

研究了搅拌头旋转速度n与焊接速度v之比即n/v比值大小对LY12铝合金搅拌摩擦焊接头组织和力学性能的影响。结果表明,n/v比值较小时,焊接线能量较小,接头存在孔洞缺陷,严重降低了接头力学性能;随着n/v比值逐渐增大,孔洞缺陷尺寸逐渐减小;当n/v比值为5时,焊接线能量适当,接头无缺陷,焊核区为细小均匀的等轴晶,因此接头强度最高,达427MPa;当n/v比值继续增大,焊核区晶粒组织也随之粗化,接头强度逐渐降低。     

The Effects of Laser Peening and Shot Peening on Mechanical Properties in Friction Stir Welded 7075-T7351 Aluminum

Peening techniques like laser peening and shot peening were used to modify the surface of friction stir welded 7075-T7351 Aluminum Alloy specimens. The tensile coupons were machined such as the loading was applied in a direction perpendicular to the weld direction. The peening effects on the global and local mechanical properties through the different regions of the weld were characterized and assessed. The surface hardness levels resulting from various peening techniques were also investigated for both sides of the welds. Shot peening resulted in an increase to surface hardness levels, but no improvement was noticed on the mechanical properties. In contrast, mechanical properties were improved by laser peening when compared to the unpeened material.     

焊接参数对7075铝合金搅拌摩擦焊接头组织及腐蚀行为的影响

不同参数下对1．6mm厚7075铝合金板进行了搅拌摩擦焊接,在分析了焊缝表面组织的基础上,采用浸泡试验对焊缝表面的腐蚀行为进行研究,讨论了硬度分布与腐蚀发生的关系。结果表明,焊后轴肩作用区晶粒细化明显。随转速的增加,焊缝上表面热机械影响区范围加宽、轴肩作用区硬度增大。焊缝上表面腐蚀最严重的区域为轴肩作用区,在EXCO溶...     

Microstructure and Mechanical Properties in Friction Stir Welded Thick Al–Zn–Mg–Cu Alloy Plate

In this work, 20-mm-thick aluminum-alloy plates were joined via friction stir welding. The temperature gradient was reduced by reducing the surface welding heat input to achieve uniformity of the mechanical properties across the thick plate joints. The welding temperature was measured using thermocouples. The microstructures were observed via electron backscatter diff raction and transmission electron microscopy. The tensile properties of the samples sliced along the thickness direction of the j...     

Influence of Pin Offset on Microstructure and Mechanical Properties of Friction Stir Welded Mg/Ti Dissimilar Alloys

The influences of pin offset on the formation, microstructure and mechanical properties of friction stir welded joint of Ti6 Al4 V and AZ31 B Mg dissimilar alloys were investigated. The results show that sound joints are obtained at different offsets. With the offset decreasing from 2.5 to 2.1 mm, the number of Ti alloy fragments is increased, and the stir zone(SZ) is enlarged and the grains in SZ become coarser. A hook-like structure is formed at the Mg/Ti interface and its length is increased with the decrease in pin offset. The Al element has an enrichment trend at the Ti alloy side near the Mg/Ti interface when the offset is decreased, which is beneficial to the bonding of the interface. An Al-rich layer with a thickness of 3–5μm forms at the offset of 2.1 mm. All the joints fracture at the interface and present a mixed ductile-and-brittle fracture mode. The joint tensile strength is increased with the offset decreasing from 2.5 to 2.1 mm, and the maximum tensile strength of 175 MPa is acquired at the offset of 2.1 mm.     

Microstructures and Mechanical Properties of Friction Stir Spot Welded Aluminum Alloy AA2014

Friction stir spot welding (FSSW) is a relatively recent development, which can provide a superior alternative to resistance spot welding and riveting for fabrication of aluminum sheet metal structures. In the current work, FSSW experiments were conducted in 3-mm thick sheets of aluminum alloy 2014 in T4 and T6 conditions, with and without Alclad layers. The effects of tool geometry and welding process parameters on joint formation were investigated. A good correlation between process parameters, bond width, hook height, joint strength, and fracture mode was observed. The presence of Alclad layers and the base metal temper condition were found to have no major effect on joint formation and joint strength. Friction stir spot welds produced under optimum conditions were found to be superior to riveted joints in lap-shear and cross-tension tests. The prospects of FSSW in aluminum sheet metal fabrication are discussed.     

2524-T3薄板搅拌摩擦焊接微观组织与力学性能

在水冷辅助工艺条件下对1.8mm厚的2524-T3铝合金板进行搅拌摩擦焊单道对接焊试验,并对焊接接头力学性能、断口形貌、显微硬度进行了分析.结果表明,在转速2400 r/min、焊速150 mm/min、随动冷却水压为0.4 MPa时,可获得表面纹理均匀细腻、无变形无飞边、无缺陷的对接接头.接头平均抗拉强度为409 MPa,达到母材的92.9％.说明该铝合金薄板采用水冷辅助工艺能获得良好效果.     

7075铝合金搅拌摩擦焊接头组织与力学性能研究

利用搅拌摩擦焊方法对7075铝合金板进行焊接,探讨了焊接速度和搅拌头旋转速度等焊接工艺参数对焊缝成形及接头力学性能的影响,并对焊接接头的显微组织进行了分析.结果表明:采用搅拌摩擦焊焊接7075铝合金时,焊接接头具有较好抗拉性能.当旋转速度为750r/min、焊接速度为95 mm/min时,焊接接头的强度最高,达到母材抗拉强度(487 MPa)的97.4％,并且其伸长率也较高(为3.1％);当旋转速度为950 r/min、焊接速度为150 mm/min时焊接接头的伸长率最好,为4.7％.总体上看,焊接接头的伸长率和母材相比较低.     

铝合金搅拌摩擦焊搭接接头工艺及组织性能研究

对铝合金3003进行一系列的搅拌摩擦搭接焊试验,并对焊接接头的工艺及组织性能进行了分析。试验结果表明:焊接接头可分为3个区域:焊核区、热机械影响区和热影响区,各区域的组织有明显的特征。当搅拌头的旋转速度为1120 r/min,焊接速度为50mm/min时,焊缝成型良好,当焊接工艺参数选择不恰当时,会产生飞边、沟槽、隧道型缺陷、钩状缺陷及波浪状曲线等缺陷。同时该旋转速度下各焊接速度所对应的抗拉强度普遍较高,基本可以达到母材抗拉强度的75%以上。在搭接焊核区硬度较高,有的甚至超过母材,在上板前进侧的热影响区硬度达到最低值。     

搅拌摩擦焊接工艺对7075-T651铝合金力学性能的影响

采用锥台结构搅拌针对7075-T651铝合金实施搅拌摩擦焊,并进行了背部二次补焊和不同温度的固溶热处理,对焊态接头的力学性能进行了研究。结果表明,二次焊接可提高接头的综合力学性能;热处理可提高焊头硬度,但强度和伸长率有所下降,且随着热处理温度的升高,裂纹沿S线扩展,导致晶粒异常长大。     

Microstructure and Mechanical Properties of Low-Carbon Q235 Steel Welded Using Friction Stir Welding

This study focuses on the microstructure and mechanical properties of the joints of Q235 mild steel, which was formed by the friction stir welding (FSW). The results indicated that, after the FSW, the heat-affected zone (HAZ) of the retreating side (HAZ_RS) and the HAZ of the advancing side (HAZ_AS) recovered under the influence of the heating cycle. The transformation of the phases in the thermo-mechanically affected zone (TMAZ) of the retreating side (TMAZ_RS), the stir zone (SZ) and the TMAZ of the advancing side (TMAZ_AS) generated the pearlite and acicular ferrite. The continuous dynamic recrystallization occurred in all the three zones, whereas the grains were refined. The SZ mainly consisted of D₁, D₂ and F shear textures, while the TMAZ_AS was made up of only the F shear texture. The fine-grained structure, pearlite and the acicular ferrite improved the hardness and tensile strength of the joint. Its ultimate tensile strength was 479 MPa, which was 1.3% higher than that of the base metal. However, the uniform elongation was 16%, which showed a decrease of 33%. The fracture was a ductile fracture with the appearance of dimples. Besides, the joints of the FSW showed an excellent bending performance.     

Microstructure and Mechanical Properties of Friction Stir Welded 1.5 GPa Martensitic High-Strength Steel Plates

In this study, 2.4 mm thick high-strength martensitic steel plates with a tensile strength of 1500 MPa were friction stir welded at various welding speeds of 40, 60, 80, 100, 120 mm/min and a constant rotation speed of 300 rpm. Sound joints could be obtained when the welding speed was 40, 60 and 80 mm/min, while a kissing bond was found in the joint welded at 100 and 120 mm/min. It was revealed that the peak temperature exceeded A_C3 (the end temperature at which all ferrite transformed to austenite when the steel was heated) for all the welding conditions and martensitic structures were finally formed in the stir zone of the joints. A significant decrease in hardness was located in the heat-affected zone, which had a transitional microstructure from tempered martensite near base metal to a mixed structure containing hard martensite, soft ferrite and bainite near stir zone. For the sound joints, the specimen was fractured in the heat-affected zone during tensile tests and the highest tensile strength could reach about 1058 MPa.     

Study on Microstructure and Mechanical Properties of Friction Stir Welded Aluminium Alloy Thick Plate

对14 mm厚板铝合金搅拌摩擦焊(FSW)接头焊核区微观组织、整体和分层切片力学性能进行了研究。结果表明, 当旋转速度为400 r/min, 焊接速度为60-100 mm/min时, 接头抗拉强度σ　b、屈服强度σ0.2和延伸率δ随焊速的升高而降低。焊缝分层切片的σ b, σ　0.2和δ上部最高, 分别达到了186.7 MPa, 100.3 MPa和14.1%;下部最低, 分别为157.5 MPa, 80.2 MPa和10.1%。微观断口中存在大量的网状韧窝, 切片上部韧窝最深, 焊缝根部可见沿晶界的二次裂纹和浅韧窝。显微硬度分布为焊缝上部高于下部, 沿焊缝中心呈不对称分布. 焊核区上部等轴再结晶晶粒尺寸大于焊缝下部. 焊核区上部的第二相粒子相对下部更均匀和细小, 强化作用增强.     

Homogeneity of Mechanical Properties of Underwater Friction Stir Welded 2219-T6 Aluminum Alloy

Underwater friction stir welding (FSW) has been demonstrated to be available for the improvement in tensile strength of normal FSW joints. In order to illuminate the intrinsic reason for strength improvement through underwater FSW, a 2219 aluminum alloy was underwater friction stir welded and the homogeneity of mechanical properties of the joint was investigated by dividing the joint into three layers. The results indicate that the tensile strength of the three layers of the joint is all improved by underwater FSW, furthermore, the middle and lower layers have larger extent of strength improvement than the upper layer, leading to an increase in the homogeneity of mechanical properties of the joint. The minimum hardness value of each layer, especially the middle and lower layers, is improved under the integral water cooling effect, which is the intrinsic reason for the strength improvement of underwater joint.     

焊接速度对7075铝合金搅拌摩擦焊接头强度和微观组织的影响

采用搅拌摩擦焊方法对7075铝合金板进行了焊接实验,探讨了焊接速度对接头强度和微观组织的影响.结果表明,焊速对焊接接头的焊核区、热机影响区及晶界沉淀相均有较大的影响.随着焊速的提高,焊核区的晶粒和沉淀相大小、形状、分布密度均发生较大变化,热机影响区的变形程度和形貌也发生了较大改变.组织和力学性能综合分析表明,选择合理的焊接速度有利于细化焊核区的晶粒组织,改善焊缝成型,提高焊接接头强度.     

焊后热处理工艺和背部二次焊接对搅拌摩擦焊接7075-T651铝合金性能的影响

对8 mm厚7075-T651铝合金轧制板进行了搅拌摩擦焊接,重点研究了焊后热处理工艺和背部二次焊接对接头性能的影响.结果表明,焊接态接头致密没有缺陷,接头强度约为母材的71%.T6热处理后,焊核区出现由锯齿形裂纹和微孔组成的"S"线.随着固溶温度升高,"S"线愈加明显,并伴有晶粒异常长大现象.T6热处理后,接头硬度恢复到母材水平,但强度和延伸率显著下降,这是由于裂纹沿"S"线产生和扩展所致.在焊态样品背面进行二次焊接,可明显改善接头的力学性能.     

异种铝合金搅拌摩擦焊搭接接头的显微组织与硬度研究

采用搅拌摩擦焊对异种铝合金6061-T6(上板)和A356-T6(下板)进行搭接焊,用体式和光学显微镜观察搭接接头的组织形貌,并测试其显微硬度.结果表明:在适当的工艺参数条件下,可以获得表面成形良好、内部无明显缺陷的搭接接头.在焊核区,两板间存在明显的界面,且位置较原位置整体上移,前进侧界面处呈锯齿状,界面由两种铝合金组织交替镶嵌而成,而后退侧界面则呈曲线状.两板均呈现典型的搅拌摩擦焊接头组织:焊核区由细小的等轴晶组成,而热影响区组织与母材相似,晶粒有细微粗化,热机影响区晶粒被拉长、弯曲,有明显的塑性流动.两板焊缝区显微硬度比各自母材均有不同程度的降低,且上板6061-T6降低幅度较大,焊后最大硬度约为母材的65%.