AZ31镁合金氩弧焊接接头组织与力学性能研究

钨极氩弧焊(TIG)为镁合金焊接中最常用的一种焊接方法。本文采用直流钨极氩弧焊对6.0 mm厚AZ31镁合金挤压板材进行了双面焊接实验。采用光学显微镜、扫描电镜、拉伸试验机考察分析了焊接接头显微组织与力学性能。显微组织分析表明,AZ31镁合金直流TIG焊接头由母材、热影响区、焊缝区组成,焊缝组织呈现焊丝熔化后凝固组织;在母材热影响区与焊缝区之间坡口处形成过渡区,晶粒细小,为母材与焊丝的熔合区。采用AZ31焊丝焊接接头平均抗拉强度为241.0 MPa,延伸率为13.8%,分别达到了母材的86.0%和63.6%。焊接接头的断裂均位于热影响区,断口呈现韧脆混合断裂特征。     

AZ31B镁合金TIG和MIG焊接接头组织性能比较分析

研究了AZ31B镁合金钨极氩弧焊(TIG)和熔化极氩弧焊(MIG)焊接接头组织及性能。在厚度为8.0 mm的AZ31B镁合金板材上分别进行了填丝TIG和MIG两种焊接试验,分析了AZ31B镁合金两种焊接工艺以及接头焊缝的微观组织和显微硬度。试验结果表明,填丝TIG焊缝成形良好;MIG焊接时有飞溅现象,焊缝成形不及TIG均匀。TIG和MIG焊接接头的相组成与母材的相组成一致。MIG焊接热影响区HAZ的晶内析出相弥散分布,焊缝区晶界析出相连续分布;而且MIG焊接接头的显微硬度值较TIG焊接时要高,焊接接头的力学性能有所提高。     

AZ31镁合金薄板的交流钨极氩弧焊

探讨了氩弧焊工艺参数对镁合金焊接接头质量的影响，采用金相显微镜，对AZ31镁合金薄板TIG焊接接头进行了微观组织观察、用X-射线衍射仪等分析测试手段对相组成和力学性能进行了分析，结果发现：焊接电流为40A和45A时，焊接接头的力学性能最好，(σb为205MPa)，为母材强度的80％左右，断裂总是发生在热影响区，焊缝区组织呈细小的等轴晶，主要存在α-Mg和Mg17Al12两种相，热影响区组织较粗大。     

CO2激光焊接快速凝固耐热铝合金AA8009

采用3种不同的焊接速度（0.6, 1.5和2.4 m/min）, 对板厚为1 mm的耐热铝合金AA8009进行CO2激光焊接. 研究结果表明： 在焊接冷却速度为102～103 ℃/s时, 焊缝中心凝固组织为亚共晶组织, 大量细小的第二相粒子弥散分布在细小近等轴的α-Al中;在熔化区边界存在大量粗大的针状相分布在粗大胞状枝晶α-Al中;提高焊接速度可改善焊接接头组织和性能, 当焊接速度为2.4 m/min时, 焊缝组织类似于基材组织;焊接接头断裂发生在熔化区边界.     

镁合金焊丝成分对镁钢异种金属CMT焊接性的影响

采用CMT冷金属过渡焊对异种金属AZ31B镁合金板和HDG60镀锌钢板进行焊接,试验中采用AZ92、AZ61、MnE21镁合金焊丝.结果表明:在合适的工艺参数下,3种焊丝都能形成较好的焊缝,但AZ92、AZ61焊丝的焊接窗口比较宽,而MnE21焊丝的焊接窗口极窄,并且焊缝处有明显的裂纹.接头的界面组织分析表明,焊接接头被分成焊缝区、中间结合区、熔合区.通过X射线衍射分析得出,当采用AZ92、AZ61镁合金焊丝时,焊接结合面主要有Mg的固溶体,还有MgFeAlO4、Mg2Zn11、Al12Mg17等化合物;采用MnE21镁合金焊丝时,焊接结合面主要有Mg固溶体,还有Mg32Al49、Al12Mg17化合物.在拉伸试验中,采用相同规格的拉伸试样,使用AZ61焊丝的接头拉剪力可达镁母材的87.5%.而采用其他2种焊丝时拉剪力较小.由此可见,AZ61焊丝更适合焊接镁钢异种金属.     

焊接电流对镁/镀锌钢 TIG熔--钎焊接头显微组织与力学性能的影响

采用TIG熔-钎焊焊接方法,以镁合金焊丝为填充材料,对镁合金与镀锌钢进行连接实验,并分析热输入量对接头显微组织和力学性能的影响.热输入量过小会阻碍镁/钢界面反应层的形成而使得焊缝难以焊合,热输入量过大又会促进焊缝内部脆性第二相的长大,降低接头力学性能.接头强度随着焊接电流和焊接速度的增大都呈现先上升后下降的趋势,电流为70 A时强度达到最大,该值接近AZ31B母材的88．7%.此时断裂发生于焊缝熔焊区,断面出现大量韧窝和撕裂棱,呈现出塑性断裂特征.     

焊接热输入对镁合金与镀铜钢冷金属过渡焊接接头性能和缺陷影响

利用冷金属过渡焊(CMT)对镁合金和镀铜钢异种金属进行焊接,填充材料选择AZ31镁合金焊丝,对焊接接头的显微组织进行检测,分析焊接接头的性能和缺陷。实验结果表明:Cu元素对镁合金在钢表面的润湿铺展起到良好的促进作用,焊接热输入影响Cu元素对镁/钢表面的润湿铺展效果。焊接接头产生富铜区,易产生裂纹,降低了焊接接头强度。经过拉伸测试,在焊接热输入为212. 2 J/mm时,焊接接头强度达到最大值3. 99 k N,但在焊接热输入达到254. 6 J/mm时,焊接强度反而降低,这是由于钎焊区生成了大量的中间层脆性化合物。焊接接头组织中检测到气孔、夹渣和裂纹等焊接缺陷的存在,这与母材表面的氧化膜和焊缝内应力有关。     

ME20M变形镁合金的TIG焊工艺研究

探讨了ME20M变形镁合金TIG焊工艺参数的选择,采用金相显微镜、拉伸试验机以及扫描电子显微镜等表征方法对焊接接头的微观组织、力学性能以及断口形貌等进行了分析.结果发现,焊接电流为80 A时,焊接接头成形较好,焊缝区组织呈细小的等轴晶,热影响区组织较粗大;焊缝区的硬度由于晶粒细化的原因而有所提高,在热影响区则有所下降;拉伸试验表明焊接接头的力学性能低于母材的力学性能,接头抗拉强度约为母材抗拉强度的75%左右.拉伸断口扫描形貌分析表明,断口呈韧-脆混合断裂.     

微弧氧化处理提高AZ31B镁合金搅拌摩擦焊焊缝的耐蚀性

为提高镁合金焊接接头的耐蚀性,对6mm厚的AZ31B板材搅拌摩擦焊焊缝进行微弧氧化处理,并研究焊缝的微观组织、截面显微硬度及其微弧氧化前后的耐蚀性.结果表明:接头的微观组织明显分为3个区域:焊核区、热机械影响区及热影响区,并且接头整体硬度低于母材,焊接时焊核部位出现软化现象,导致其硬度最低.盐水浸泡实验和电化学测试表明,微弧氧化前焊缝的耐蚀性低于母材,经过微弧氧化处理后,焊缝表面形成一层致密光滑的陶瓷膜,极大提高其耐蚀性.并且,经同工艺微弧氧化处理后,焊缝表面微弧氧化膜要比母材的微弧氧化膜厚.     

7075铝合金点焊接头的组织及性能分析

采用中频逆变直流点焊机进行7075铝合金点焊焊接试验,并对焊接接头的显微组织和力学性能进行研究.结果表明:焊接接头结构分为熔化区、部分熔化区和热影响区,其熔核的部分熔化区组织为柱状晶,熔化区组织为等轴晶,热影响区及母材仍保持轧制组织形态,而且焊接接头内存在枝晶偏析;7075铝合金点焊接头的熔核硬度较低;在所用的试验条件下,7075铝合金点焊接头均在界面断裂,断裂形式为准解理脆性断裂,且塑性、韧性较差,其原因在于焊接接头的强度低于母材,以及熔化区铝合金元素偏析严重.     

Characteristics of AZ31 Mg alloy joint using automatic TIG welding

The automatic tungsten-inert gas welding (ATIGW) of AZ31 Mg alloys was performed using a six-axis robot. The evolution of the microstructure and texture of the AZ31 auto-welded joints was studied by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The ATIGW process resulted in coarse recrystallized grains in the heat affected zone (HAZ) and epitaxial growth of columnar grains in the fusion zone (FZ). Substantial changes of texture between the base material (BM) and the FZ were detected. The {0002} basal plane in the BM was largely parallel to the sheet rolling plane, whereas the c-axis of the crystal lattice in the FZ inclined approximately 25° with respect to the welding direction. The maximum pole density increased from 9.45 in the BM to 12.9 in the FZ. The microhardness distribution, tensile properties, and fracture features of the AZ31 auto-welded joints were also investigated.     

热输入对Q460钢焊接接头组织及拉伸变形行为的影响

以Q460钢为对象，研究了埋弧焊热输入对其接头组织及其拉伸变形行为的作用规律与机理.结果表明:接头HAZ宽度随热输入增加而增大，同时FZ柱状晶比例也增加，FZ靠近熔合线的组织明显细化，且FZ的软化得到改善.热输入对接头整体强度无明显影响，而断裂延伸率呈增加趋势.19.0kJ/cm下焊接接头FZ与HAZ界面的变形不协调，导致过早发生断裂.随热输入的增加，FZ组织细化，缓解了FZ与HAZ界面硬度差，提高了接头的塑性变形能力，拉伸断裂位置由FZ转移至BM.     

Influence of CO2 laser welding parameters on the microstructure, metallurgy, and mechanical properties of Mg-Al alloys

This study investigated the microstructural characteristics, metallurgy, microhardness, and tensile strength of AZ31 and AZ61 magnesium alloy weldments, fabricated in a CO₂ laser welding process with the adjustment of various parameters. The results show that the AZ31 weldment contains equiaxed grains within the fusion zone (FZ). By contrast, the FZ of the AZ61 weldment contains refined cellular grains and the partially melted zone (PMZ) contains bulk grains. We infer that the difference in aluminum content between the two magnesium alloys results in different supercooling rates and solid grain structures. For both weldments, the ultimate tensile strength (UTS) decreases following the CO₂ laser welding process. However, no significant difference is noted between the UTS of the two weldments, suggesting that tensile strength is insensitive to the Al content of the magnesium alloy. The CO₂ laser welding process is shown to increase the microhardness of both magnesium alloys. Furthermore, grain refinement is responsible for the maximum hardness in the FZ of both weldments. The AZ61 weldment has a higher content of Al, resulting in a greater grain refinement.     

Development of liquid-nitrogen-cooling friction stir spot welding for AZ31 magnesium alloy joints

A liquid-nitrogen-cooling friction stir spot welding (C-FSSW) technology was developed for welding AZ31 magnesium alloy sheets. The liquid-nitrogen cooling degraded the deformability of the welded materials such that the width of interfacial cracks increased with increasing cooling time. The grain size of the stirred zone (SZ) and the heat-affected zone (HAZ) of the C-FSSW-welded joints decreased, whereas that of the thermomechanically affected zone (TMAZ) increased with increasing cooling time. The maximum tensile shear load of the C-FSSW-welded joints welded with a cooling time of 5 or 7 s was larger than that of the friction stir spot welding (FSSW)-welded joint, and the tensile shear load decreased with increasing cooling time. The microhardness of the C-FSSW-welded joints was greater than that of the FSSW-welded joint. Moreover, the microhardness of the SZ and the HAZ of the C-FSSW-welded joints increased, whereas that of the TMAZ decreased, with increasing cooling time.     

Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

The effects of the types of overlap on the mechanical properties of the friction stir spot welding (FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations, microhardness tests, and tensile tests. The results show that the microstructure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet. The average distance D between the longitudinal segment of the curved interface and the keyhole periphery, the tensile shear force, and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples. During FSSW of AZ31 and AZ61 dissimilar magnesium alloys, the irregular deformation of the longitudinal segment of the curved interface appears, while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet. Moreover, the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.     

Welded Joint Model Construction and Welding Mechanism of AZ91 Magnesium Alloy

The characteristics of the welding molten pool of AZ91 magnesium alloy were studied and the welding interface model was built using metallographic observation and scanning electorn microscope(SEM) composition analysis.The welding area was divided into heat affected zone(HAZ),liquefaction zone(LZ),rich poly zone(RPZ),sparse zone(SZ) and weld zone(WZ).The analyses of the microstructure and composition of each region show that optimizing the welding process can improve mechanical properties of weld zone.While for LZ,its tensile properties can be strengthened only by improving the composition of the parent metal and the second phase distribution.And the way to improve the tensile properties of LZ,RPZ,and SZ is to give priority to improve the parent metal composition and the second phase distribution,improving welding technology as the complementary method.Furthermore,based on the results above and the analyses of the microstructure and composition of welding cracks,it is found that the tensile fracture is mainly caused by the stress cracking rather than composition crack.     

高速列车用6005A铝合金厚板的焊接工艺

采用半自动MIG焊完成了厚度为12mm的6005A-T6铝合金板材的连接,通过正交试验研究了焊接工艺参数对焊接接头抗拉强度及焊缝表面质量的影响.结果表明,各工艺参数对焊接接头抗拉强度影响显著性从大到小依次为:焊接电流,焊接电压,焊接速度和预热温度.考虑焊缝表面质量因素,各工艺参数影响显著性从大到小依次为焊接速度、预热温度和焊接电流.本研究条件下最佳MIG焊接6005A-T6板材的工艺参数为:预热温度200℃,焊接电流180A,焊接电压18.0V,焊接速度12mm/s.焊接后试样接头热影响区内晶粒平均尺寸小于5μm,且无过分长大现象.焊接后板材拉断时为韧性断裂.