Al-Mg合金电子束填丝焊接头的显微组织与力学性能

采用ER5183焊丝作为填充材料,对厚度为2 mm的Al-Mg合金进行真空电子束填丝焊接,并对焊接接头的微观组织及力学性能进行分析测试。结果表明,在合适的焊接工艺条件下,获得的Al-Mg合金接头焊缝成形良好。微观分析显示,接头熔合区为柱状晶和等轴状枝晶组织,主要由α(Al)基体相和β(Al₃Mg₂)强化相组成,焊缝中存在大量的缠结位错和第二相粒子。力学性能测试表明,与母材区的硬度相比,接头熔合区的硬度有所降低。在最佳工艺条件下获得接头的抗拉强度为311.2 MPa,达母材抗拉强度的96.9%。接头拉伸断口表面分布的韧窝数量较多,呈明显的韧性断裂特征。      

焊丝成分对铝-铜异种金属熔钎焊接头钎焊界面组织与接头力学性能的影响

采用脉冲旁路耦合电弧MIG熔钎焊方法对1060纯铝和T2紫铜进行了对接焊,选用ER1100、ER5356、ER4043和ER4047四种焊丝为填充材料,研究了焊丝成分对焊接接头微观组织、金属间化合物层的厚度以及力学性能的影响规律。结果表明:4种焊丝的焊接接头均由铝侧熔合区、焊缝区和铜侧钎焊区组成,其中铜侧钎焊区又可细分为金属间化合物层区和Al-Cu共晶区两部分。焊丝中Si元素的加入可以起到阻碍铝铜原子互扩散、抑制铝铜金属间化合物生长、提高焊缝显微硬度以及抗拉强度等作用;而加入Mg元素,其效果不明显。     

Inconel 718 激光焊接接头组织与热影响区裂纹研究

采用CO2激光器对板厚为11mm的Inconel 718合金进行激光焊接,并利用金相分析和扫描电镜对Inconel 718激光焊接接头各区域组织以及热影响区显微裂纹产生的原因进行了分析。研究发现:利用激光对Inconel718进行焊接,可以获得成形良好的焊接接头;焊缝区域组织为铸造组织,从熔合线到焊缝中心由较长的树枝晶逐步变为等轴晶;热影响区因受循环热输入的影响,晶界较母材出现粗化现象,且在钉头缩颈处出现沿粗化的晶界扩展的液化裂纹,裂纹两侧存在低熔点共晶体,主要富集Nb及Mo元素,低熔点共晶体在热输入影响下发生液化是裂纹产生的主要原因。     

焊丝成分对T91/316L异种钢焊接接头微观组织和力学性能的影响

T91马氏体钢与316L奥氏体钢异种钢的焊接主要应用于超超临界机组(USC)和核电领域中的加速器驱动次临界洁净核能系统(ADS)。本研究采用ER309L、ER316L和ERNiCr-3三种不同的焊丝,使用钨极氩弧(TIG)焊对T91马氏体不锈钢和316L奥氏体不锈钢进行了焊接,并对焊接接头进行了微观组织和力学性能分析,同时研究了焊后热处理对焊接接头的影响规律。研究结果表明,使用三种焊丝获得的焊缝的微观组织都是粗大的奥氏体枝晶,且其枝晶的晶粒垂直于熔合线往焊缝中心生长。焊态下焊接接头拉伸试样在T91侧的粗晶热影响区(CGHAZ)发生脆性断裂,经过焊后热处理(750 ℃/1 h)的焊接拉伸试样的韧性断裂均发生在316L母材处,且抗拉强度显著上升,这表明焊后热处理能够提高T91/316L异种钢焊接接头的拉伸性能。在未焊后热处理状态下,使用ERNiCr-3焊丝获得的焊接接头焊缝的冲击性能优于其他焊丝。焊态下焊接接头硬度在T91侧熔合线处显著升高,而焊后热处理后T91侧熔合线处的硬度凸起几乎消失。     

316L/S32101异种金属焊接接头的显微组织与力学性能研究

目的 研究乏燃料水池用钢板316L与覆板S32101双相不锈钢的焊接性、接头不同区域显微组织特征及接头与母材之间的性能差异.方法 利用氩弧焊接技术对5 mm厚的316L底板与3 mm厚的S32101覆板以搭接的形式进行焊接,利用金相显微镜、扫描电镜、维氏显微硬度仪和电子万能材料试验机对焊接接头的宏观形貌、显微组织以及力学性能进行研究.结果 316L/S32101焊缝组织主要由铁素体基体、晶界树枝状奥氏体以及晶内细小片状奥氏体所组成;316L侧靠近焊缝处存在一个较窄的熔合区,其组织由奥氏体基体和少许细小分散的铁素体组成,而S32101侧靠近焊缝处组织则由粗大铁素体晶粒和沿晶粒边界分布的若干小块状奥氏体组成.从316L母材区到焊缝区,硬度显著增大,而从焊缝区到S32101母材区,硬度变化很小;焊接接头的抗拉强度高达510 MPa,为两侧316L和S32101母材强度的87.9％和88.6％.结论 在焊接电流为240 A和焊接速度为300 mm/min的条件下,可以通过氩弧焊获得成形良好的搭接接头,且接头的力学性能优异.     

增材制造GH3625与轧制GH3625激光焊接头组织及力学性能分析

本工作对激光增材制造GH3625(以下简称3D-GH3625)与轧制GH3625进行激光焊接试验，研究激光功率对其焊接接头的显微组织和力学性能的影响，并对其焊接接头的显微组织演变规律进行分析。结果表明，随着激光功率增加，两侧焊缝的熔合区完成由胞状晶向胞状树枝晶转变，而在激光功率相同时，厚板从上到下两侧熔合区的组织形态由上层的柱状晶和胞状晶转变为下层的柱状树枝晶，焊缝中心区由上层的柱状树枝晶和等轴树枝晶转变为下层的柱状树枝晶。当P=5.0 kW,焊接接头无明显表面缺陷、力学性能优良，抗拉强度高达861 MPa,伸长率达到50%左右，对接头断口进行分析，发现断口处有块状MC、部分撕裂棱和孔洞存在。随着激光功率的增加，接头抗拉强度从最高860 MPa下降至833 MPa。     

AZ31/7005异种材料填丝GTAW焊接接头的组织与性能

采用ER4043,ER4047铝硅合金焊丝对AZ31镁合金和7005铝合金异种材料进行填丝钨极氩弧焊(GTAW),并对AZ31/7005接头进行微观组织观察和显微硬度分析。结果表明:采用填丝钨极氩弧焊工艺,可以获得表面成形良好的焊接接头;镁侧熔合区是接头力学性能的薄弱区,镁侧熔合区不同结晶区域Mg和Al的成分较为接近,组织主要为Mg17Al12+Mg共晶体组织;靠近镁侧熔合区无高硬度脆性相产生,焊缝区的硬度稍高于镁母材区,但远低于铝母材区。     

铝锂合金自动钨极氩弧焊接工艺研究

采用自行研制的两种焊丝,进行了新型铝锂合金自动钨极氩弧焊接,测量了焊态下两种焊丝焊接接头的室温力学性能,观察了接头的显微组织和拉伸断口形貌.并采用鱼骨形抗裂实验,评定了该合金的热裂纹敏感性.实验结果表明,焊接工艺规范显著影响接头的焊缝成形,采用交流脉冲焊接方法和研制焊丝作填充材料可明显改善合金的抗裂性能,焊态下两种研制焊丝的接头强度系数均能达到60%.     

ER5356焊丝用于7075铝合金MIG焊接头热处理性能

采用MIG焊使用ER5356焊丝进行3 mm厚7075铝合金对接焊,焊后接头进行T6热处理。通过光学显微镜、X射线衍射仪、扫描电镜与能谱仪结合室温拉伸、显微硬度与电化学腐蚀分析接头组织、力学性能与耐蚀性。结果表明：焊接时熔池流动将母材熔化部位的Zn,Cu等合金元素带入焊缝,析出MgZn₂与AlCuMg相,成为焊缝进行热处理强化的基础;热处理后,大部分析出相溶入基体形成固溶+时效强化,接头抗拉强度提升20%,焊缝硬度提升18.4%,耐蚀性提高。但由于从母材流入焊缝的合金元素含量有限,焊丝与母材力学性能的差异与热影响区软化现象无法消除。     

ER5356焊丝中Sc、Zr、Er对7A52铝合金焊接性能的影响

使用传统ER5356焊丝及添加Sc、Zr、Er的ER5356焊丝对7A52铝合金进行钨电极惰性气体保护焊,研究了Sc、Zr、Er对焊接接头力学性能的影响。结果表明,在ER5356焊丝中添加Sc、Zr、Er可有效细化焊缝处的组织,提高焊接接头的强度。单独添加Sc的焊丝效果最好,焊接接头的抗拉强度可达322.5 MPa,是母材强度的70.4%。     

Carbide precipitates and mechanical properties of medium Mn steel joint with metal inert gas welding

Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160 pm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with 307Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.     

Effect of pre- and post-weld heat treatment on metallurgical and tensile properties of Inconel 718 alloy butt joints welded using 4 kW Nd:YAG laser

The effects of pre- and post-weld heat treatments on the butt joint quality of 3.18-mm thick Inconel 718 alloy were studied using a 4 kW continuous wave Nd:YAG laser system and 0.89-mm filler wire with the composition of the parent metal. Two pre-weld conditions, i.e., solution treated, or solution treated and aged, were investigated. The welds were then characterized in the as-welded condition and after two post-weld heat treatments: (i) aged, or (ii) solution treated and aged. The welding quality was evaluated in terms of joint geometries, defects, microstructure, hardness, and tensile properties. HAZ liquation cracking is frequently observed in the laser welded Inconel 718 alloy. Inconel 718 alloy can be welded in pre-weld solution treated, or solution treated and aged conditions using high power Nd:YAG laser. Post-weld aging treatment is enough to strengthen the welds and thus post-weld solution treatment is not necessary for strength recovery.     

Influence of filler metals and welding techniques on the structure–property relationships of Inconel 718 and AISI 316L dissimilar weldments

In the present investigation, an attempt has been made to weld the precipitation hardened Nickel based super alloy Inconel 718 and austenitic stainless steel AISI 316L using Continuous Current Gas Tungsten Arc Welding (CCGTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) process employing ER2553 and ERNiCu-7 fillers. Microstructure examination using optical and SEM analysis clearly witnessed the formation of unmixed zone at the Heat Affected Zone (HAZ) of Inconel 718 for all the joints. The studies showed the absence of deleterious phases in the CCGTA and PCGTA weldments employing ERNiCu-7. Tensile studies corroborated that the fracture occurred at the parent metal of AISI 316L in all the cases. It was inferred from the present study that PCGTA weldments employing ERNiCu-7 exhibited better metallurgical and mechanical properties. This study articulated the effect of filler metals on the structure–property relationships of the weldments.     

Effect of post weld heat treatment on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel weldments

The effect of postweld heat treatment (PWHT) on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel joints with ER316LMn filler material was investigated. PWHT aging was performed for 1 h at four different temperatures of 600 °C, 760 °C, 870 °C and 920 °C, respectively. The microstructure revealed the sigma phase precipitation occurred in the weld metals heat-treated at the temperature of 870 °C and 920 °C. The PWHT temperatures have the less effect on the tensile strength, and the maximum tensile strength of the joints is about 630 MPa, reaching the 95% of the base metal, whereas the elongation is enhanced with the rise of PWHT temperatures. Meanwhile, the sigma phase precipitation in the weld metals reduces the impact toughness.     

Experimental investigation of local tensile and fracture resistance behaviour of dissimilar metal weld joint: SA508 Gr.3 Cl.1 and SA312 Type 304LN

The aim of the paper is to evaluate the local tensile and fracture toughness properties of the dissimilar metal weld joints between SA508Gr.3 Cl.1 and SA312 Type 304LN pipe. Weld joints have been prepared by manual gas tungsten arc welding (GTAW) process with conventional V‐groove and automatic hot wire gas tungsten arc welding with narrow gap using different filler wires/electrode such as Inconel 82/Inconel 182 and ER309L/ER308L. The tensile and fracture toughness test specimens have been machined from different regions of dissimilar metal weld such as heat affected zones, fusion lines, buttering layer, weld metal and both base metals. Tensile and fracture toughness tests have been carried out as per the ASTM standard E8 and E1820 respectively. Tensile and fracture toughness results of all the regions of dissimilar metal weld joints have been discussed in this paper. Metallurgical and fracture surface examinations have also been reported to substantiate the tensile and fracture toughness results. Need for the local properties for integrity assessment of the dissimilar metal weld joints has also been brought out.     

Laser welding of copper‐niobium microcomposite wires for pulsed power applications

The laser welding of copper‐niobium microcomposite wires was investigated. It was determined that the joint structure does not have welding defects, while microscopic examination of the joint cross‐section showed that the microstructure of the autogenous weld consists mainly of a copper‐based solid solution strengthened by niobium‐rich precipitations. The weld obtained with use of filler material consists of two distinct zones, which are formed due to melting of filler wire and microcomposite wire. This structure of the joint provides an insignificant increase in electrical resistance and sufficient ultimate strength and plasticity of the joint. The tensile strength of the sample welded without filler material reaches 335 MPa, but such welded joints are very brittle due to very low ductility. However, an autogenous laser welding joint has about 1.6 times better ductility, and the tensile strength of the joint depends on the applied filler material and is equal to the tensile strength of this material.     

Effect of TiC Content on Mechanical Properties and Microstructure Evolution of TiC/Inconel 718 Functionally Gradient Materials by Direct Energy Deposition

TiC/Inconel 718 functionally gradient materials are prepared by direct energy deposition technology. The effect of TiC content on microstructure and mechanical properties of TiC/Inconel 718 functionally gradient materials is studied. With the increase of TiC content, the microhardness and carbide grain of the specimen are improved, and the density is reduced. The grain of the specimen changes from columnar dendrites to equiaxed crystal, and the equiaxed crystal size is decreased with the increase of TiC content. However, when TiC content is above 10 wt%, the number and size of the Laves phase, coarse TiC primary, and TiC secondary dendrite are increased which causes the generation of cracks. When the TiC content is above 5 wt%, the size of carbide and the number of cracked UMT increase and the impact toughness decreases. Therefore, the optimal maximum TiC content of TiC/Inconel 718 functionally gradient materials is 5 wt% when the laser power is 2200 W.     

Mikrostrukturelle und mechanische Eigenschaften von laserstrahlgeschweißtem Magnesiumfeinblech AZ31‐HP mit und ohne Zusatzwerkstoffe

Microstructural and mechanical properties of laser welded sheets of magnesium AZ31‐HP with and without filler wires This paper describes Nd:YAG laser beam welding experiments carried out on rolled 2.5 mm thick magnesium sheet AZ31‐HP. For the butt welds in flat position, filler wires AZ31X and AZ61A‐F were used, diameter 1.2 mm. The microstructure and mechanical properties of the different laser beam welded joints were examined and compared with one another. The obtained results show that the laser beam welding of AZ31‐HP sheet is possible without hot crack formation, both without and with filler wires. The determined tensile strength, ductility, fracture toughness and microhardness of laser beam welded joints without filler wire were not effected by AZ31X nor AZ61A‐F. By use of these filler wires loss of zinc was minimized and the shape of weldments was optimized. The values of fracture strength, yield strength and microhardness of the joints and base material are quite similar. It is found that the ductility of the joints is lower than the base materials due to the heterogeneous microstructure of the fusion zones and geometrical notches of the weld seams. Both, weld and base material of AZ31‐HP, showed stable crack propagation. Furthermore, for base material slightly lower fracture toughness values CTOD than for the joints were determined.