铜/钛合金电子束焊接工艺优化

研究了QCr0.8/TC4电子束焊接工艺及接头组织,由于铜合金热导率高而熔化量较小,以及焊缝中生成大量脆性金属间化合物相,因此对中焊时接头强度较低.采用偏铜侧进行非对中电子束焊接,接头抗拉强度随偏束量的增大而增高,偏束量为0.8mm时接头最高抗拉强度为270.5MPa.断裂发生在TC4侧熔合线处,为脆性准解理断裂特征.偏铜焊时接头成形得到改善,焊缝包括熔合区及TC4侧反应层两部分.熔合区主要由铜基固溶体组成,硬度较TC4母材有所降低.反应层成分过渡较大,含有多种金属间化合物相.随着工艺参数的变化,反应层厚度也发生变化,从而对接头性能产生影响.     

高氧TC4/TC17钛合金线性摩擦焊接头组织特征及力学性能

对高氧TC4/TC17异质钛合金进行线性摩擦焊试验,研究了焊接接头各区域组织特征、焊接界面合金元素扩散行为及力学性能. 结果表明,焊接过程中焊缝区发生了相变及动态再结晶,形成细小的等轴晶粒. 高氧TC4侧焊缝区形成针状马氏体,TC17侧形成亚稳定β相;两侧热力影响区晶粒均发生了破碎,沿着振动方向拉长. 焊后冷却阶段在焊合线附近出现合金元素扩散现象,扩散区域狭窄. 焊缝中心处显微硬度值最高达到420 HV,高氧TC4侧显微硬度随着靠近母材而逐渐降低;TC17侧显微硬度随着远离焊缝中心迅速升高. 拉伸性能测试结果表明,接头抗拉强度与高氧TC4母材相当.     

薄板TC4钛合金脉冲电子束焊接技术研究

脉冲电子束焊接是指将电子束流调制成脉冲方波的形式进行焊接的一种先进技术。脉冲束流能提高被焊金属蒸发率,从而提高焊接效率、增加焊缝深宽比。本文采用常规直流电子束和不同频率脉冲电子束对1.2 mm薄板TC4钛合金进行了焊接工艺试验,并对接头进行了微观组织与力学性能检测。结果表明：脉冲电子束焊接能够形成无熔合缺陷的焊缝,随着频率的增加,焊缝咬边和背面余高减小,表面成形得到改善;由于焊接热循环变化,脉冲束流可加快熔池冷却速度,细化组织晶粒;直流和脉冲电子束焊接接头拉伸时均断裂在母材区,拉伸强度不低于母材;高频脉冲电子束可提升焊接接头塑性和焊缝区、热影响区的显微硬度,频率为10 kHz时,焊接接头的断后伸长率可达14.9%,约为母材的80%,焊缝区和热影响区的显微硬度分别为375 HV和368 HV。     

7A52铝合金电子束焊接参数及性能

对20mnrl厚7A52铝合金板材采用试件法进行电子束焊接,确定了焊接参数并对力学性能进行分析．结果表明,采用加速电压60kV,电子束流120mA,聚焦电流763mA,焊接速度800mm／min,可得到良好的焊缝表面．电子束流增大焊缝深宽比显著增加,聚焦电流微小的数值变化可引起焊缝形状突变．接头焊缝区晶粒细小均匀,抗拉强度为母材的87％,焊缝维氏硬度最低值为母材的61％,焊缝冲击韧度为母材的95．4％,表明了电子束接头的性能很高．     

Effect of welding processes on joint characteristics of Ti–6Al–4V alloy

Abstract

Although Ti–6Al–4V alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Microstructures and tensile and impact properties of welded Ti–6Al–4V alloy were evaluated for high vacuum electron beam welding, CO₂ laser beam welding and gas tungsten arc welding. The resultant tensile and impact properties of the welded joints are correlated with the weld metal microstructure and hardness. The results indicate that the electron beam welding is more suitable for Ti–6Al–4V sheet welding and the welding seam without defects can be obtained. The full penetration butt welds are obtained by gas tungsten arc welding process, but they have many drawbacks such as wide weld seam, big deformation and coarse grains. Laser beam welding has many advantages such as the narrowest weld seam, the least deformation and the finest grains, but it should be studied again for the reasons of unstable welding technologies and strict condition.     

高铌TiAl/Ti600合金电子束焊接头组织与性能

对高铌TiAl/Ti600合金进行了电子束焊接试验以便对高温钛合金与高铌TiAl合金高质焊接提供理论及试验依据,采用金相显微镜、扫描电子显微镜及X射线衍射仪等设备对焊接试样进行了分析.结果表明,高铌TiAl/Ti600接头极易产生裂纹缺陷.接头焊缝主要形成细针状α₂-Ti₃Al相及α-Ti相,而高铌TiAl侧热影响区呈现板条状及等轴组织形貌,Ti600侧热影响区为针状α'相.接头焊缝区硬度最大,达到586 HV,Ti600侧向高铌TiAl侧过渡过程中硬度逐渐增大,由焊缝到两侧热影响区硬度过渡梯度较大.高铌TiAl/Ti600电子束焊接头室温抗拉强度可达516 MPa,且接头断裂于偏高铌TiAl侧焊缝区,断裂性质为典型的脆性解理断裂,呈现穿晶断裂特征.     

钛合金(TC4)电子束焊接模拟

通过工艺试验,获得了9 mm厚TC4电子束焊接最佳工艺参数;利用有限元软件ABAQUS建立模型.结果表明,模拟焊缝形貌和表面残余应力结果与实测结果具有非常高的一致性,说明了穿透性强的圆锥热源和辐射性强的双椭球热源组成的复合热源能够有效地反应出电子束焊接特点,证明了有限元模型的正确性;进而对模拟结果进一步分析,得到焊缝周围存在较高残余应力,尤其是在焊件内部存在危险的三维拉伸应力状态.     

焊接电流对Ti2AlNb/TC18焊接界面性能及元素扩散的影响

采用真空电子束焊接对Ti2AlNb和TC18合金进行连接,研究了不同焊接电流时焊接界面的性能及元素扩散情况。结果表明:焊接接头在室温和高温下均获得了较高的抗拉强度。采用同一电流焊接时,TC18侧热影响区的显微硬度值高于该合金基体却低于该侧焊缝区,而Ti2AlNb合金侧热影响区的显微硬度值均高于该侧焊缝区和Ti2AlNb合金基体;在28 mA的焊接电流下,焊接界面的整体显微硬度值均较高,这是因为焊接界面形成了含量较多且尺寸较小的α′马氏体和O相,对界面起到了强化作用。在不同的焊接电流下,合金元素均在焊缝和两侧母材交界处存在较大的浓度梯度,其原因是焊缝金属的快速凝固使得各合金元素没有足够的时间和能量进行充分扩散。     

TC4钛合金水下湿法激光焊接焊缝组织与性能

使用光纤激光器对TC4钛合金进行了水下湿法激光焊接试验,通过在TC4表面预置焊接辅助剂实现了增加水下湿法焊接熔深的同时对焊缝进行保护的目的. 对焊缝的微观组织和力学性能进行了分析,结果表明,预置焊接辅助剂后,焊缝熔深增大,焊接阈值增加,焊缝中裂纹减少. 焊缝中心主要由初生α和马氏体组织α'相组成,在熔池底部还保留有粗大的β晶界,焊缝由于水的急冷作用出现了淬硬组织,显微硬度远高于TC4母材. 水下焊接拉伸试验试件均断裂在焊缝处,焊接接头平均抗拉强度值为439 MPa,呈现为脆性断裂.     

TiAl金属间化合物电子束焊接头应力场分布特征

采用热弹塑性有限元方法,对TiAl金属间化合物平板电子束焊接接头的焊接应力进行了三维数值模拟,并分析了应力分布状态与裂纹特征之间的关系.结果表明,沿焊缝方向σx为残余拉应力,在焊道中部维持在较高水平,最高拉应力为390MPa.焊道中部横截面σx方向为残余拉应力,在热影响区附近达到最大值415 MPa,σy方向也为残余拉应力,且在距焊缝中心1.9 mm处达到最高值160 MPa左右.在不同焊接热输入条件下接头最高抗拉强度为304.7 MPa,断裂发生在接头热影响区附近,即残余应力最大的区域.     

热输入对TiAl基合金电子束焊接头性能的影响

采用不同的焊接工艺参数对Ti43Al9V0.3Y(原子分数,%)合金进行电子束焊接,分析了不同的焊接热输入对接头组织、焊缝成形及抗拉强度的影响.结果表明,随焊接热输入的增大接头的抗拉强度也增大,但热输入过大时强度降低.TiAl基合金性能对组织非常敏感,电子束焊接时接头组织转变不充分造成变形能力差,极易形成宏观横向裂纹和纵向弧坑微裂纹.近缝区组织和硬度过渡剧烈,是接头中的薄弱环节,因此裂纹大多从弧坑扩展到近缝区而断裂.断裂性质为脆性断裂,断裂特征为解理断裂和穿晶断裂,还具有分层、穿层的断裂特征.     

Effects of zonal heat treatment on residual stresses and mechanical properties of electron beam welded TC4 alloy plates

Zonal heat treatment(ZHT) was conducted in situ to 14.5 mm-thick TC4 alloy plates by means of defocused electron beam after welding. The effects of ZHT on residual stresses, microstructures and mechanical properties of electron beam welded joints were investigated. Experimental results show residual stresses after welding are mostly relieved through ZHT, and the maximum values of longitudinal tensile stress and transverse compressive stress reduce by 76% and 65%, respectively. The tensile strength and ductility of welded joint after ZHT at slow scanning velocity are improved because of the reduction of residual stress and the microstructural changes of the base and weld metal. ZHT at fast scanning velocity is detrimental to the ductility of welded joint, which is resulted from insufficiently coarsened alpha phase in the fusion zone and the appearance of martensite in the base metal.     

Double-sided gas tungsten arc welding process on TC4 titanium alloy

TC4 titanium alloy was welded by double-sided gas tungsten arc welding（GTAW） process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results indicate that double-sided GTAW is superior over regular single-sided GTAW on the aspects of increasing penetration, reducing welding deformation and improving welding efficiency. Good weld joint was obtained, which can reach 96.14% tensile strength and 70.85% elongation percentage of the base metal. The grains in heat-affected zone（HAZ） are thin and equiaxed and the degree of grain coarsening increases as one moves to the weld center line, and the interior of grains are α and α′ structures. The coarse columned and equiaxed grains, which interlace martensitic structures α′ and acicular α structures, are observed in weld zone. The fracture mode is ductile fracture.     

TC4厚壁管全位置PAW工艺及接头性能分析

介绍了一种适合TC4钛合金厚壁管的等离子弧焊接新工艺,通过对工艺参数分区控制和优化匹配,实现了钛合金管道全位置优质焊接.采用光学显微镜、扫描电镜以及显微维氏硬度仪分别对特征位置焊接接头的显微组织、断口形貌以及显微硬度进行表征.结果表明,特征位置接头焊缝区及热影响区显微组织均主要由网篮状α'相、针状α相以及粗大β相组成;接头拉伸性能良好,拉伸试样均断裂于母材处;冲击试样的断裂形式为韧性断裂;焊缝区及热影响区硬化区的硬度值高于母材.     

PM-TZM钼合金电子束焊接特性

为研究PM-TZM钼合金电子束焊接特性,对其进行了电子束焊接试验,分别对接头显微组织及力学性能进行了分析. 结果表明,PM-TZM钼合金电子束焊缝呈“钉状”几何特征,熔合线附近有链状气孔出现. 焊缝区由粗大的等轴晶及柱状晶组成,热影响区晶粒相比于母材明显长大. 接头各区域硬度值不同,焊缝区硬度与母材相当,硬度最低值出现在两侧热影响区.PM-TZM合金电子束焊接接头有较大的性能损失. 接头室温最高抗拉强度378 MPa,为母材抗拉强度的47%,1 000℃抗拉强度168 MPa. 接头拉伸断裂均发生于焊缝区,呈典型的脆性解理断裂特征.     

Inconel 718镍基合金与304不锈钢电子束焊接

对Inconel 718镍基合金与304不锈钢进行了电子束焊接试验,分析了接头显微组织及力学性能. 结果表明,焊缝区中部由枝晶及细小的等轴晶组成,在近镍侧及近钢的熔合线,都由向焊缝中心方向生长的树枝晶组成. 各特征区域显微硬度值各不相同,焊缝区高于镍基合金侧,高于不锈钢侧. 当焊接束流为8 mA,焊接速度为700 mm/min时,接头的抗拉强度最高为722 MPa. 拉伸试样断裂发生于焊缝区内部,呈典型的延性断裂,断口可观察到明显等轴状韧窝.     

35mm厚板铝合金搅拌摩擦焊接头组织和性能

采用搅拌摩擦焊双面焊工艺,对35 mm厚板6005A-T6铝合金型材进行了搅拌摩擦焊接,获得成形良好、表面光滑、无隧道孔和沟槽缺陷的焊接接头.应用光学显微镜、扫描电镜、显微硬度仪及电子拉伸试验机等对搅拌摩擦焊接头组织与性能进行研究.结果表明,接头焊核区组织为细小等轴晶;前进侧出现明显的螺旋纹及清晰的结合线,热力影响区晶粒被明显拉长呈条状组织,热影响区受热晶粒粗大;后退侧未见螺旋纹,晶粒比前进侧细小,过渡区较前进侧宽.在搅拌头旋转频率为650 r/min,焊接速度为200 mm/min工艺条件下接头抗拉强度为213 MPa,达到母材强度的84.8%,断裂起始于焊缝前进侧的热影响区,扩展至双面焊接重合区时,沿着焊缝后退侧热影响区直至断裂;接头显微硬度最低值出现在前进侧热影响区,最低值为50 HV.     

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.     

Microstructure and high-temperature mechanical properties of laser beam welded TC4/TA15 dissimilar titanium alloy joints

The microstructure evolution and high-temperature mechanical properties of laser beam welded TC4/TA15 dissimilar titanium alloy joints under different welding parameters were studied. The results show that the weld fusion zone of TC4/TA15 dissimilar welded joints consists of coarsened β columnar crystals that contain mainly acicular α′ martensite. The heat affected zone is composed of the initial α phase and the transformed β structure, and the width of heat affected zone on the TA15 side is narrower than that on the TC4 side. With increasing temperature, the yield strength and ultimate tensile strength of the TC4/TA15 dissimilar welded joints decrease and the highest plastic deformation is obtained at 800 °C. The tensile strength of the dissimilar joints with different welding parameters and base material satisfies the following relation (from high to low): TA15 base material > dissimilar joints > TC4 base material. The microhardness of a cross-section of the TC4/TA15 dissimilar joints reaches a maximum at the centre of the weld and is reduced globally after heat treatment, but the microhardness distribution is not changed. An elevated temperature tensile fracture of the dissimilar joints is located on the side of the TC4 base material. Necking occurs during the tensile tests and the fracture characteristics are typical when ductility is present in the material.     

TiAl/TiAl和TiAl/TC4真空电子束焊接头组织结构及焊接性

对TiAl自体及TiAl／TC4异体对接接头进行了不同焊接参数下的电子束焊接试验。通过光学金相、能谱分析及SEM断13形貌分析等方法对TiAl自体焊及TiAl／TC4异体焊接头区的显微组织结构及断裂性质进行了分析。研究结果表明,TiAl／TiAl焊缝为树枝状TiAl铸态组织,TiAl／TC4焊缝为支晶近Ti3Al铸态混合组织;接头拉伸断裂为脆性解理断裂,接头的力学性能对接头显微组织非常敏感;TiAl／TC4接头拥有比TiAl／TiAl接头较好的可焊性。