ULCB钢电子束穿透焊组织与性能

为了进一步探索ULCB钢的焊接性能,采用真空电子束穿透焊不同束流强度对14 mm钢板对接接头进行了焊接,通过焊缝形貌比较,束流强度为100 mA时,接头焊缝成形最好,选取该接头做了拉伸、硬度、冲击试验及金相组织分析.结果表明,拉伸试样的断裂区域在母材区,抗拉强度为761 MPa、屈服强度为669 MPa,硬度范围在270~330 HV;冲击试样的断裂区域在热影响区,焊缝区平均冲击功为288 J,热影响区平均冲击功为273 J;接头显微组织中,焊缝区和热影响区产生了α'马氏体相,使焊缝区和热影响区产生相变强化,导致焊接接头的强度和硬度均高于母材.     

船用5083铝合金变极性等离子焊接头组织和性能

采用变极性等离子焊接工艺实现了5mm厚船用5系铝合金立向上位置焊接,并分析了接头的组织和力学性能。力学试验显示：接头抗拉强度达到295MPa,延伸率达到10%,断裂位置在熔合线附近;焊缝区和热影响区的显微硬度均低于母材,且焊缝中心处最低。接头金相观察发现熔合线附近的焊缝为粗大的等轴晶组织,但焊缝区大部分为胞状树枝晶组织,从两侧呈对称生长并在焊缝中心处相遇,热影响区为再结晶组织。利用电子探针分析了拉伸断裂位置附近成分,发现该区域Mg含量偏低且分布不均匀,固溶强化效果下降,组织和成分的不均匀导致该区域成为接头的薄弱环节。     

Explosively welded copper‐stainless steel bimetal and an example of its application

Summary

Friction welding was carried out under various welding conditions using high strength 7075 aluminium alloy; an investigation into the structure and the mechanical properties of joints thus obtained leads to the following conclusions: The fibrous structure at the heat affected zone changed to align in the direction of flash expulsion and the fibrous structure at the weld zone disappeared and a non-directional fine grain structure was evident. The hardness at the weld interface had a lower value than that of the base metal and an even more softened zone than the weld interface was noted at the heat affected zone. The hardness values at the weld interface and the softened zone were seen to recover after friction welding due to natural ageing but did not recover fully. Both the values of the tensile strength and the elongation declined compared with the base metal in joints made under the conditions that gave the maximum value of tensile strength; the former was 81% and the latter was 83% that of the base metal. The joint impact value of a specimen with a notch on the weld interface was 73% that of the base metal.     

热处理对TC17(α+β)/TC17(β)线性摩擦焊接头组织及力学性能的影响

针对热处理前后TC17(α+β)/TC17(β)钛合金线性摩擦焊接头组织和性能进行了对比分析. 结果表明,焊态时焊缝区组织发生动态回复和再结晶,两侧的热力影响区组织均被不同程度地拉长,热处理后焊缝中的亚稳相分解析出弥散的α和β相,TC17(α+β)侧热力影响区的初生α相有所长大. 焊态接头焊缝区显微硬度比母材低,接头的抗拉强度和屈服强度略低于母材,分别达到母材的91.9%,96.2%,接头拉伸性能试件断裂位置均在焊缝区;经过热处理,母材显微硬度未发生明显变化,焊缝区显微硬度显著提高,接头抗拉强度和屈服强度达到与母材相当,与焊态相比分别提高11.9%,8.2%,接头拉伸性能试件断于母材区.     

铝合金激光-多股绞合焊丝MIG复合焊接头组织与性能分析

选用1 × 3结构的ER5356铝合金多股绞合焊丝,进行5A06铝合金激光-多股绞合焊丝MIG复合焊对接试验,通过金相、扫描电镜、电子背散射衍射、拉伸和硬度测试等方法对20 mm厚焊接接头的微观组织和力学性能相关性进行分析. 结果表明,铝合金激光-多股绞合焊丝MIG复合焊工艺性较好,焊缝主要由α(Al)基体和弥散分布的Al₃Mg₂第二相组成,焊缝中心区以等轴晶为主,晶粒的平均尺寸为34.83 μm;热影响区晶粒细小,存在回复再结晶,晶粒的平均尺寸为10.21 μm. 焊接接头硬度在75 ~ 90 HV之间,其中熔合区硬度值最低,为母材硬度值的84.6 %;焊接接头平均抗拉强度292 MPa,为母材抗拉强度的84 %,拉伸试件断口断裂位置为熔合区附近,呈现出韧性断裂特征.     

Incoloy 825镍基高温合金电子束焊工艺及接头组织与力学性能分析

采用电子束焊,对空冷器管箱Incoloy 825镍基高温合金进行对接焊试验. 通过对焊接接头的组织观察,并结合拉伸力学性能以及接头的冲击韧性等试验,分析镍基高温合金电子束焊接头的组织和力学性能. 结果表明, 采用电子束焊焊接镍基高温合金可以得到良好的焊接接头,焊缝区组织由大片等轴晶和少量柱状晶组成;焊缝区没有出现明显的元素烧损现象;焊缝、热影响区硬度达到母材硬度值;焊缝接头抗拉强度达到600 MPa,接近母材抗拉强度,接头断裂形式为韧性断裂;焊缝和热影响区的冲击吸收能量高于母材区,其中焊缝区的冲击吸收能量达到了262 J,冲击断口形貌为韧窝状.     

不同成形状态2195铝锂合金GTAW焊接头的组织与性能

采用喷射沉积2195铝锂合金旋态和锻态材料进行了GTAW对接焊,检测了接头抗拉强度和维氏硬度,观察了接头金相组织及断口形貌,对接头各区域进行了EBSD表征和微观特征量的统计分析,讨论了接头微观组织与力学性能的相关性.结果表明,旋、锻态材料具有良好的GTAW工艺性,接头抗拉强度达到了各自母材的71％和68％,断后伸长率达...     

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.     

热输入对超高强钢DP1000激光焊接接头微观组织和断裂机制的影响

利用光学显微镜（OM）、扫描电子显微镜（SEM）观察超高强双相钢DP1000激光焊接接头微观组织的变化,通过显微硬度的测试、拉伸试验研究其不同热输入下焊接接头的力学性能.结果表明,随着热输入的增加,由回火区和两相区组成的软化区的组织发生了明显的变化,软化区内平均硬度值减小,其宽度尺寸增加,导致拉伸试样的断裂位置发生变化.当热输入不高于52 J/mm,焊接试样的抗拉强度是母材的97.75%,软化区宽度最大约为506 μm,断裂发生在母材上;当热输入达到72 J/mm,软化区宽度约为621 μm,断裂发生在软化区内.     

7475铝合金回填式FSSW接头微观组织与力学性能研究

本文针对7475铝合金回填式搅拌摩擦点焊展开研究,首先采用不同工艺参数对2mm 7475铝合金进行焊接,然后对焊点表面和横截面进行观察,同时对试样进行硬度测量和拉伸剪切测试。结果表明,根据焊缝微观组织可以将焊点分为四个部分,不同部位的晶粒尺寸不同;并在微观组织中发现了Hook、孔洞和未连接等由于材料流动性不佳造成的微观组织缺陷;同时,母材区和搅拌区的硬度明显高于热影响区和热机影响区;另外,焊点的最高硬度和拉伸剪切强度随着焊具旋转速度、搅拌套下压深度的变化而呈现规律性变化,但是搅拌套运动速率对焊点力学性能的影响不明显。     

CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

Effectiveness of cold metal transfer process for welding 7075 aluminium alloys

Abstract

Cold metal transfer (CMT) welding is a promising process to improve the mechanical characteristics of the hard to weld 7075-T6 aluminium alloy owing to its unique advantages in contrast to conventional metal inert gas welding process. The welded joints, using ER5356, were identified and characterised by means of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Mechanical properties were measured by tensile and hardness tests. Results indicate that CMT provides better joint tensile strength and ductility compared to metal inert gas welding. The softness in the heat affected zone was very low, but a big hardness gap was recognised in the welded metal compared to base metal. The joint had mechanical property coefficients of 77%, 60% and 69% for yield strength, ultimate tensile strength and elongation respectively.     

AZ71镁合金TIG焊焊接接头微观组织与力学性能

采用钨极氩弧焊接方法对2.2mm厚镁合金AZ71薄板进行焊接加工。焊后对接头进行拉伸试验和硬度测试,结果表明:采用90A的电流焊接时,接头抗拉性能最好(281.23MPa),达到母材的89.58%。断裂发生在焊缝区,焊接接头断口呈准解理断口,接近解理断口;母材断裂为延性断裂,断口呈韧窝断口;焊缝区显微硬度最高,其次是母材,热影响区硬度最低。     

Microstructure and mechanical properties of the joint of 6061 aluminum alloy by plasma-MIG hybrid welding

Plasma-MIG (metal inert gas arc welding) hybrid welding of 6061 aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out.The microstructures and mechanical properties of the welded joint were investigated by optical microscopy,X-ray diffraction (XRD),energy dispersive spectroscopy (EDS),tensile test,hardness test and scanning electron microscope (SEM) were used to judge the type of tensile fracture.The results showed that the tensile strength of welded joint was 142 MPa which was 53.6％ of the strength of the base metal.The welding seam zone was characterized by dendritic structure.In the fusion zone,the columnar grains existed at one side of the welding seam.The fibrous organization was found in the base metal,and also in the heat affected zone (HAZ) where the recrystallization occurred.The HAZ was the weakest position of the welded joint due to the coarsening of Mg2Si phase.The type of tensile fracture was ductile fracture.     

Microstructure and Its Influence on the Mechanical Properties of Ni–28W–6Cr-Based Alloy-Welded Joints by GTAW

Microstructure and mechanical properties of Ni–28W–6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work.Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding.Carbides with different shapes were found in the weld metal and base metal, which all were determined as M6C carbides.In comparison with carbides in base metal, M6C carbides in weld metal are rich in Si and Cr but deficient in W.Moreover, M6C carbides are extremely scarce and hard to be detected in weld metal.Mechanical tests show that the hardness value of weld metal is only about 60% of base metal; the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.     

Microstructures and mechanical properties of bonding layers between low carbon steel and alloy 625 processed by gas tungsten arc welding

A filler metal wire, Alloy 625, was cladded on a plate of a low carbon streel, SS400, by gas tungsten arc welding, and the morphology of the weld bead and resulting dilution ratio were investigated under different welding parameter values (the input current, weld speed and wire feed speed). The wire feed speed was found to be most influential in controlling the dilution ratio of the weld bead, and seemed to limit the influence of other welding parameters. Two extreme welding conditions (with the minimum and maximum dilution ratios) were identified, and the corresponding microstructures, hardness and tensile properties near the bond line were compared between the two cases. The weld bead with the minimum dilution ratio showed superior hardness and tensile properties, while the formation lath martensite (due to relatively fast cooling) affected mechanical properties in the heat affected zone of the base metal with the maximum dilution ratio.     

Microstructure characterization and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy

The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses were utilized to characterize the weld nugget, heat affected zone and base metal. The AA6111 spot welds displayed a softer nugget and hardened heat affected zone, compared with the base metal. The through-thickness hardness of the base metal sheet was not constant and had to be carefully considered to determine the effect of welding on material properties. Quasi-static lap-shear tensile tests were used to determine the failure load and failure mode. All tensile specimens failed through the interfacial fracture. This failure mode is consistent with the observed reduced hardness in the weld nugget.     

异种高温钛合金电子束焊接接头组织与性能

采用真空电子束焊机对高温钛合金Ti60板材和Ti700sr铸件进行焊接,并对接头显微组织和力学性能进行了研究. 结果表明,高温钛合金Ti60板材和Ti700sr铸件电子束焊接性良好,可以获得优质的接头. 获得的接头中焊缝为细小针状马氏体组织,Ti700sr侧熔合区马氏体内部存在层错和孪晶. Ti700sr侧热影响区相比于母材网篮状的α相长大. Ti60侧熔合区和热影响区均发现富Nd稀土弥散相析出. 焊缝区显微硬度与Ti60和Ti700sr母材相当,基本在360 HV左右.硬度最高点出现在Ti60侧热影响区,硬度最大值达到418 HV.接头室温抗拉强度达到1 100 MPa以上,断裂于Ti60热影响区. 接头600 和650 ℃高温抗拉测试均失效断裂在Ti60母材. 其中接头600 ℃高温拉伸性能均值为695 MPa,650 ℃高温拉伸性能均值为587 MPa.     

FSS/ASS厚壁异种钢“TIG冷焊 + UNGW”组合焊的接头组织与力学性能

为了有效解决铁素体不锈钢的焊接热影响区晶粒易粗化问题，以及奥氏体不锈钢焊接时在接头部分熔合区及其附近热影响区内因易形成蠕虫状δ铁素体而显著降低该区域耐腐蚀性的问题，提出了“TIG冷焊 + UNGW”的组合焊接工艺，并进行了1Cr17/1Cr18Ni9Ti厚壁异种不锈钢的焊接，同时对所得接头的显微组织、力学性能及耐腐蚀性进行了测试与分析. 结果表明，组合焊接头的1Cr17母材热影响区晶粒未发生粗化，并且1Cr18Ni9Ti母材部分熔合区及其附近热影响区内未形成蠕虫状δ铁素体；组合焊接头的抗拉强度优于1Cr17母材，并且1Cr17母材热影响区的冲击吸收能量与1Cr17母材相当；组合焊接头的熔敷层、1Cr18Ni9Ti母材、1Cr17母材、UNGW焊缝区及完整接头的耐腐蚀性呈依次下降的趋势.     

TC4钛合金线性摩擦焊接头组织和力学性能

文中阐述了线性摩擦焊的原理、特点,并针对TC4钛合金线性摩擦焊接头组织和力学性能进行了研究.对比分析TC4钛合金线性摩擦焊接头焊态和焊后热处理态的接头组织和力学性能.结果表明,焊接接头共分为母材、热力影响区和焊缝区三部分;TC4钛合金的接头(包括焊态和焊后热处理态)抗拉强度和屈服强度均达到母材的90%以上;焊缝中心的硬度值最高,焊后热处理能使接头的硬度分布更加均匀.