焊接速度对GTA焊接AZ31B镁合金接头组织和拉伸性能的影响

研究焊接速度对脉冲电流钨极惰性气体保护焊接（PCGTAW）AZ31B镁合金接头组织和拉伸性能的影响。实验中焊接速度为105-145 mm/min。结果表明,焊接速度为135 mm/min时,所得接头具有最好的拉伸性能。在熔合区生成的细小晶粒组织和均匀分布的析出相是导致较好的拉伸性能的主要原因。     

镁合金交流TIG和脉冲TIG组织性能分析

采用交流TIG和交流脉冲TIG两种焊接方法焊接变形镁合金AZ31B板材,利用高速摄像机和红外热像仪研究稳定焊接过程中的电弧形态和焊接温度场,观察焊接接头的微观组织并进行力学性能拉伸试验.发现脉冲焊接在峰值电流加热时的电弧形态明显大于交流TIG焊接时的电弧.对比焊接温度分布曲线可以看到,脉冲焊接时熔池两侧区域的冷却速度更快.脉冲焊接接头的热影响区更窄,而且晶粒更细小均匀.拉伸结果显示交流脉冲TIG焊接接头强度高于交流TIG焊接接头强度.     

AZ31B-AZ91D异种镁合金自动弧焊工艺研究

本文利用焊接机器人夹持氩弧焊炬对AZ31B-AZ91D异种镁合金自动弧焊工艺进行了研究,并在焊后利用金相显微镜、扫描电子显微镜、电子能谱仪和拉伸试验机等先进手段对焊接接头的微观组织、析出相类型、拉伸性能及断口形貌进行了表征分析。研究结果表明,在焊接电流130A、焊接速度0. 65m/min、填丝速度0. 7m/min、正面保护气体流量16L/min、背面保护气体流量19L/min的焊接工艺条件下,可得到外观形貌良好的AZ31B-AZ91D异种镁合金焊接接头。邻近焊接接头AZ31B一侧的微观组织可以清晰地分为AZ31B母材区,热影响区和焊接熔化区,邻近AZ91D一侧析出相数量明显增多,EDS分析结果表明,该析出相为β-Mg17Al12相。拉伸结果显示,AZ31B-AZ91D异种镁合金焊接接头的屈服强度、抗拉强度和断后延伸率分别达到了AZ31B母材的76. 38%、88. 45%和42. 77%。表明该焊接接头力学性能优异。焊接接头拉伸断口形貌呈现出韧性-脆性复合断裂特征。     

焊接电流变化对镁合金TIG焊接的影响

采用TIG焊接方法焊接AZ31B镁合金,采用宏观分析、显微组织、显微硬度、拉伸强度等分析方法对研究了焊接电流对镁合金焊接接头微观组织和力学性能的影响。结果表明:随着焊接电流的增加,镁合金焊接接头拉伸强度先增加后减小,焊接电流为110 A时达到最大值193 MPa。镁合金焊接接头热影响区和熔合区显微硬度随焊接电流增加逐渐降低,晶粒尺寸逐渐增大。焊缝熔宽随焊接电流增大逐渐增加,焊缝深宽比先增加后减小。     

AZ31镁合金板材点焊接头的力学性能与断裂特征

用交流点焊机焊接了AZ31镁合金板材,测试了不同表面清理状态下点焊接头的力学性能,用光学显微镜和扫描电镜分析了接头的显微组织和拉伸断口形貌.结果表明:在其它参数不变的情况下,接头的拉剪强度随电极压力的增加先增大,后减小,中间有个峰值;焊接电流和焊接时间对接头断裂强度的影响规律与电极压力相似.表面清理状态对接头的质量有很大影响,焊前未经过清理的接头强度较低;焊前经机械打磨的接头总体焊接质量较好;焊前采用化学清理的接头,质量稳定,接头强度随焊接电流的增大而提高.焊缝组织由等轴晶和柱状晶构成,拉伸断口呈韧脆混合的断裂特征.     

AZ31B镁合金焊接接头组织特征及力学性能

采用钨极氩弧焊(TIG)焊接AZ31B镁合金,研究了焊接接头的微观组织,并分析了接头的力学性能.结果表明,选择45-60A焊接电流,快速填丝焊可使焊接接头的力学性能达到母材的90％以上,焊接性能良好.拉伸试验中,焊接试样断裂位置多发生在晶粒粗大的热影响区,经扫描电子显微镜(SEM)分析,接头呈韧性-脆性混合断裂.     

AZ31B镁合金搅拌摩擦焊接头的组织与性能

对我国航天工业中常用的6.6 mm厚的AZ31B镁合金进行了搅拌摩擦焊试验,获得了型面良好、表面质量光滑、检测无缺陷的焊接接头。对比分析了镁合金在不同工艺参数下的焊接接头拉伸、硬度以及断裂等力学性能;同时,研究了AZ31B镁合金搅拌摩擦焊在不同区域的显微组织结构。结果表明,焊接接头抗拉强度达到250 MPa,为母材的89.3%,焊接接头硬度大于母材硬度,接头断裂位置位于前进边热力影响区附近;焊核区晶粒大小均匀,热力影响区晶粒大小不一,存在焊核区塑性流动和搅拌头的转动双重作用结构,从而论证了航天AZ31B镁合金搅拌摩擦焊的可行性。     

电流加载方式对AZ31B镁合金板材拉伸变形行为的影响

为了探究脉冲电流加载方式对AZ31B镁合金板材拉伸变形行为的影响,通过单向拉伸实验研究了脉冲电流加载方式(持续加载与间断加载)和加载时间对AZ31B镁合金板材塑性的影响,结合试样温度场分布分析了电流辅助拉伸过程中试样宽度与厚度方向的应变分布,并观察了不同电脉冲电流参数条件下的微观组织。结果表明,脉冲电流间断加载能够有效提高材料塑性,降低变形抗力,在占空比为40%、电流加载时间为9 s条件下,AZ31B镁合金板材伸长率达到40. 5%,并且发现在脉冲电流作用下,试样温度分布不均匀,从而导致了应变不均匀。此外,脉冲电流作用下AZ31B镁合金在较低温度下发生了不同程度的晶粒长大。     

AZ31镁合金/镀锌钢异种金属TIG熔钎焊接头组织与力学性能研究

以AZ31B镁合金焊丝为填充材料,采用TIG熔钎焊工艺对AZ31B镁合金板与镀锌钢板进行连接。采用光学显微镜、SEM、XRD、万能拉伸试验机等检测方法研究了焊接电流对AZ31B镁合金/镀锌钢熔钎焊接头微观组织及力学性能的影响。结果表明:采用TIG熔钎焊工艺可以实现AZ31B镁合金与镀锌钢的可靠连接,接头具有典型的鱼尾纹特征。当焊接电流较小时,镁/钢界面有大量孔洞生成,接头结合强度较低;当焊接电流大于75A时,镁/钢界面有Mg_(32)(Al,Zn)_(49)、Al_2Mg和Al Fe_3等金属间化合物生成,镁/钢接头具有最大的抗拉强度210 MPa;随着焊接电流继续增大,镁/钢界面的脆性反应层逐渐增厚,接头力学性能有所降低。     

AZ31B镁合金搅拌摩擦焊工艺优化

采用搅拌摩擦焊(FSW)对AZ31B及加0.5%Ce的AZ3IB镁合金板材进行焊接试验.通过正交试验对FSW焊接工艺参数进行了优化.对于AZ31B镁合金,FSW最佳工艺方案为:轴肩下压量0.19mm,转速1400r/min,焊速40mm/min;对于添加0.5%Ce的AZ31B镁合金,FSW焊接的最佳工艺方案为:轴肩下压量0.17mm,焊速40mm/min,转速1300r/min.对加0.5%Ce的AZ31B镁合金FSW正交试验分析得出的最佳方案进行了验证,结果表明,焊接接头的拉伸强度为250.76MPa,延伸率为8.56%,断裂位置为热影响区.     

Fatigue crack growth behaviour of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

The laser beam welded joints offered better resistance against the growing fatigue cracks compared to friction stir welded and pulsed current gas tungsten arc welded AZ31B magnesium alloy joints. The formation of very fine grains in weld region, higher fusion zone hardness, uniformly distributed fine precipitates and favourable residual stress field of the weld region are the main reasons for superior fatigue performance of laser beam welded joints of AZ31B magnesium alloy.     

Influences of pulsed current parameters on mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloys

This paper reveals the influences of pulsed current parameters, namely peak current, base current, pulse frequency and pulse-on time, on the mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloys. Twenty joints were fabricated using different levels of peak current, base current, pulse frequency and pulse-on time. The tensile properties of the welded joints were evaluated and correlated with the weld zone’s microstructure and hardness. Optical microscopy, scanning electron microscopy and X-ray diffraction were used to evaluate the metallurgical characteristics of the welded joints. The joints fabricated using a peak current of 210 A, base current of 80 A, pulse frequency of 6 Hz and pulse on time of 50 % yielded tensile properties superior to the other joints. The formation of fine grains in the weld region, higher fusion zone hardness and uniformly distributed precipitates are the main reasons for the superior tensile properties of these joints.     

Influences of pulsed current parameters on mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloy

This paper reveals the influences of pulsed current parameters, namely peak current, base current, pulse frequency and pulse-on time, on the mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloys. Twenty joints were fabricated using different levels of peak current, base current, pulse frequency and pulse-on time. The tensile properties of the welded joints were evaluated and correlated with the weld zone’s microstructure and hardness. Optical microscopy, scanning electron microscopy and X-ray diffraction were used to evaluate the metallurgical characteristics of the welded joints. The joints fabricated using a peak current of 210 A, base current of 80 A, pulse frequency of 6 Hz and pulse on time of 50 % yielded tensile properties superior to the other joints. The formation of fine grains in the weld region, higher fusion zone hardness and uniformly distributed precipitates are the main reasons for the superior tensile properties of these joints.     

Optimizing pulsed current gas tungsten arc welding parameters of AA6061 aluminium alloy using Hooke and Jeeves algorithm

Though the preferred welding process to weld aluminium alloy is frequently constant current gas tungsten arc welding （CCGTAW）, it resulted in grain coarsening at the fusion zone and heat affected zone（HAZ）. Hence, pulsed current gas tungsten arc welding（PCGTAW） was performed, to yield finer fusion zone grains, which leads to higher strength of AA6061 （Al-Mg-Si） aluminium alloy joints. In order to determine the most influential control factors which will yield minimum fusion zone grain size and maximum tensile strength of the joints, the traditional Hooke and Jeeves pattern search method was used. The experiments were carried out based on central composite design with 31 runs and an algorithm was developed to optimize the fusion zone grain size and the tensile strength of pulsed current gas tungsten arc welded AA6061 aluminium alloy joints. The results indicate that the peak current （Ip） and base current （IB） are the most significant parameters, to decide the fusion zone grain size and the tensile strength of the AA6061 aluminum alloy joints.     

Study on ac-PMIG welding of AZ31B magnesium alloy

Abstract

Welding of AZ31B magnesium alloy is carried out using alternating current pulsed metal inert gas (ac-PMIG) welding with 1·6 mm diameter of filler wire. Typical current waveform is used to make sure arc given an accurate energy input into filler wire. The arc characteristics, metal transfer forms, microstructure and mechanical property of ac-PMIG welding of AZ31B magnesium are investigated. The results show that a stable welding procedure and continuous joints can be obtained easily under a wide range of welding parameters. The most important factors for ac-PMIG welding are negative electrode (EN) ratio and pulse rework current, which give an accurate energy input into filler wire. The grain in fusion zone is much finer and more uniform, and grain size does not grow significantly in the heat affected zone compared with base metal. The average ultimate tensile strength of weld beads is 97·2% of base metal.     

镁合金薄板焊接性能研究

采用钨极交流氩弧焊焊接方法制备了0.8 mm厚的AZ31和AZ80镁合金拼焊板,分析了AZ31和AZ80镁合金拼焊板的焊接性能,确定了钨极交流氩弧焊接工艺参数.研究结果表明,AZ31镁合金焊缝处的晶粒为等轴晶,热影响区组织是树枝状晶.AZ31-AZ80拼焊板的焊缝处缺陷主要是气孔和热裂纹.焊缝性能与焊接母材的性能相当.     

Effect of process parameters of pulsed current tungsten inert gas welding on weld pool geometry of titanium welds

The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded (GTAW) titanium alloy was analysed. Four factors, five levels, central composite design were used to develop empirical relationships, incorporating pulsed current parameters and weld pool geometry.     

镁合金钨极氩弧焊接头深冷强化机制

针对镁合金焊接接头软化问题,文中提出了AZ31镁合金TIG焊接接头深冷强化方法,进行了镁合金TIG焊接工艺试验和焊接接头的-160℃,8 h深冷处理试验;深冷处理使镁合金焊接接头抗拉强度从212.4 MPa提高到246.6 MPa;用X射线衍射仪(XRD)和透射电子显微镜(TEM)等观测了焊接接头深冷前后的微观组织与结构,分析了焊接接头深冷强化机理.结果表明,深冷处理使镁合金TIG焊接接头形成亚晶结构,第二相Mg17Al12颗粒弥散析出,提高了基体连续性,第二相颗粒数量增加,使接头组织细化并获强化,深冷处理使焊接接头的晶粒发生转动与位错转化为位错环,使接头组织产生孪晶,强化了焊接接头.