随机后热处理对TiNi记忆合金精密脉冲电阻对焊接头性能的影响

采用拉伸测试、SEM、TEM和定点成分能谱分析等手段研究了随机后热处理对TiNi形状记忆合金精密脉冲电阻对焊焊接接头力学性能、形状恢复率的影响,并对影响接头力学性能和形状恢复率的接头组织和形貌进行了研究,得出了获得具有较高形状恢复率接头的焊接参数,从微观角度揭示了随机后热处理提高接头形状恢复率的内在原因,为TiNi形状记忆合金的开发和应用提供了基础,具有重大的理论和实际应用价值。     

薄片状TiNi形状记忆合金的激光对接焊

采用低功率脉冲激光对厚度为0.2mm的TiNi形状记忆合金进行了对接焊,研究了接头的抗拉强度、断裂应变、相变过程和形状记忆效应.试验发现,低功率脉冲激光能够实现薄片状TiNi合金的良好焊接.冷轧态TiNi合金焊后接头的强度达到母材的97%,断裂应变为母材的95%,对接头进行焊后退火处理其强度有所提高,高于冷轧态母材、达到退火态母材的63.6%,断裂应变为退火态母材的82.5%.冷轧态TiNi合金焊接接头经焊后退火处理,其相变过程和退火态母材接近,形状记忆效应基本和退火态母材相同.     

TiNi形状记忆合金片激光微焊接接头的组织性能

采用脉冲激光实现了0.2mm厚TiNi形状记忆合金的对接焊,研究了焊接接头的抗拉强度、断裂形貌、组织和相变过程。结果表明,脉冲激光能够实现薄片状TiNi形状记忆合金的良好对接焊,焊接接头的抗拉强度可达683MPa,为冷轧态母材的97%,断口形貌与母材相似,均为延性断裂。根据晶粒尺寸和显微组织的不同,接头可分为4个区。焊缝中心区为细小的等轴晶,而焊缝边缘为柱状晶组织。对焊接接头进行焊后退火处理后其相变过程与退火态TiNi形状记忆合金的接近。     

TiNi形状记忆合金电阻钎焊技术

利用自行研制的数控交流电阻焊机，采用CuNi薄带钎料，配合改进型钎剂对TiNi形状记忆合金丝材的电阻钎焊技术进行了研究，分析了焊接热量、焊接时间、焊接压力及保护气体等参数对接头力学性能的影响规律，得到了获得优异力学性能的TiNi合金丝接头的最佳焊接参数。试验结果表明，焊接热量对接头的力学性能有着显的影响。研究结果表明，电阻钎焊技术可实现TiNi合金的可靠连接。     

铝合金/镀锌钢板脉冲MIG电弧熔-钎焊接头组织与性能

采用数字化脉冲MIG焊机,以ER4043焊丝为填充材料.实现了6013-T4铝合金薄板与镀锌钢板的熔-钎焊接,研究了焊接热输入对接头组织和性能的影响,结果表明,在熔-钎焊接头熔化焊缝焊趾处存在主要由Zn-Al共晶体、富A1的α固溶体和Fe3Al组成的富Zn区:钎焊界面上的Fe-Al金属间化合物层厚度在1.05-4.50μm之间.且随焊接热输入的增加而增大.Fe-Al金属间化合物呈"锯齿"或"舌"状向焊缝内生长,主要为FeAl₂,Fe₂Al₅和Fe₄Al₁₃.随着焊接热输入的增大,熔-钎焊接头的抗拉强度先增大而后减小.在850 J/cm的热输入下达到229 MPa,拉伸后在铝合金焊接热影响区发生断裂,为塑韧性断裂;当焊接热输入较小时接头在钎焊界面断裂,属于脆性断裂.     

Microstructures and properties of welded joint of TiNi shape memory alloy and stainless steel

The fracture characteristics of the joint were analyzed by means of scanning electron microscope(SEM).Microstructures of the joint were examined by means of optical microscope, SEM and an image analyzer. The results show that the tensile strength of the inhomogeneous joint of TiNi shape memory alloy and stainless steel is lower than that of the homogeneous joint and a plastic field appears in the heat affected zone on the side of TiNi shape memory alloy. Because TiNi shape memory alloy and stainless steel melted, a brittle as-cast structure was formed in the weld. The tensile strength and the shape memory effect of the inhomogeneous joint are strongly influenced by the changes of composition and structure of the joint. Measures should be taken to reduce the base metal melting and prevent the weld metal from the invasion by O for improving the properties of the TiNi shape memory alloy and stainless steel inhomogeneous joint.     

TiNi形状记忆合金与不锈钢激光焊接头裂纹分析及防止措施

采用激光焊对TiNi形状记忆合金与不锈钢异种材料进行焊接,用扫描电镜和激光共聚焦显微镜研究了TiNi合金/不锈钢接头裂纹及断口特征,分析了焊缝裂纹的形成机理,并提出了防止裂纹的措施.结果表明,裂纹多以微裂纹的形式出现于焊缝中心和TiNi合金侧熔合区.焊缝中存在大量的脆性化合物是产生裂纹的内在原因,接头受到拉伸应力是产生裂纹的必要条件,焊缝裂纹是二者共同作用的结果.通过焊接区加镍和钴中间层材料、改变激光光斑位置、焊接区施加轴向力及优化激光焊接参数的方法均能在一定程度上改善焊缝金属的裂纹敏感性,其中加金属中间层效果更为明显,加镍和钴中间层后,接头抗拉强度分别达到372和347 MPa,比未加中间层的接头的抗拉强度分别提高98.9%和85.6%.     

Friction welding of Al–Mg–Si alloy to Ni–Cr–Mo low alloy steel

Abstract

It is difficult to weld the dissimilar material combination of aluminium alloys and low alloy steels using fusion welding processes, on account of the formation of a brittle interlayer composed of intermetallic compound phases and the significant difference in physical and mechanical properties. In the present work an attempt has been made to join these materials via the friction welding method, i.e. one of the solid phase joining processes. In particular, the present paper describes the optimisation of friction welding parameters so that the intermetallic layer is narrow and joints of acceptable quality can be produced for a dissimilar joint between Al-Mg-Si alloy (AA6061) and Ni-Cr-Mo low alloy steel, using a design of experiment method. The effect of post-weld heat treatment on the tensile strength of the joints was then clarified. It was concluded that the friction time strongly affected the joint tensile strength, the latter decreasing rapidly with increasing friction time. The highest strength was achieved using the shortest friction time. The highest joint strength was greater than that of the AA6061 substrate in the as welded condition. This is due to the narrow width of the brittle intermetallic layer generated, which progressed from the peripheral (outer surface) region to the centreline region of the joint with increasing friction time. The joints in the as welded condition could be bent without cracking in a bend test. The joint tensile strength in the as welded condition was increased by heat treatment at 423 K (150° C), and then it decreased when the heat treatment temperature exceeded 423 K. All joints fractured in the AA6061 substrate adjacent to the interface except for the joints heated at 773 K (500° C). The joints fractured at the interface because of the occurrence of a brittle intermetallic compound phase.     

脉冲宽度对超薄TiNi/不锈钢激光焊接头TiNi侧界面的影响

添加Ni做为填充材料是抑制TiNi/不锈钢异种材料激光焊接头裂纹从而实现其良好连接的方法之一,但填充金属Ni与母材TiNi合金的成分差异会形成界面区,焊接热输入对界面区的组织形貌有很大的影响,进而会影响整个接头的力学行为。本文在厚度为0.2mm的TiNi合金/321不锈钢异种材料激光微焊接时,预置Ni做为填充材料,获得了TiNi合金/Ni/321不锈钢激光焊接头,研究了激光脉冲宽度对焊接接头TiNi侧界面的影响。结果表明,不同脉冲宽度下,TiNi合金侧界面区均由宽度不等的TiNi共晶层和TiNi₃金属间化合物层组成;随着脉冲宽度的增加,TiNi共晶层平均宽度逐渐减小,TiNi₃金属间化合物层平均宽度逐渐增加;界面区显微硬度随脉冲宽度的增加逐渐升高。TiNi母材熔化量和Marangoni流动的改变是影响接头该侧界面区宽度及显微硬度的主要原因。     

TiNi形状记忆合金与不锈钢的储能焊

采用储能焊焊接TiNi形状记忆合金与不锈钢异质接头，研究了两种母材及接头的力学性能，在光学显微镜、扫描电镜及能谱仪上观察分析接头的断口形貌和微观组织。结果表明：TiNi形状记忆合金与不锈钢异质接头的抗拉强度较低并且脆。由于不锈钢与TiNi形状记忆合金熔化，在接头处形成铸态组织及脆性化合物，改变了TiNi形状记忆合金成分和组织，异质接头的记忆效应和抗拉强度受到严重影响。为了提高异质接头的性能．焊接时应尽量避免各种缺陷并将焊缝中多余熔化金属挤出。     

Microstructures and properties of capacitor discharge welded joint of TiNi shape memory alloy and stainless steel

0IntroductionTiNi SMAis a newkind of functional material used inmany fields,such as aviation and spaceflight,atomic ener-gy,ocean development,instruments and medical purpo-ses,etc.due to its special SME and superelasticity,aswell as excellent erosion resi…     

添加铜箔中间层的NiTi形状记忆合金超声波焊接

采用超声波焊接方法对添加铜箔中间层的NiTi形状记忆合金进行搭接焊,研究接头的表面形貌、界面形貌、相变行为、抗拉性能和断裂特点. 结果表明,超声波焊接能实现添加铜箔中间层的薄片状NiTi形状记忆合金的有效连接. NiTi焊缝表面存在明显压痕,界面处结合良好,无金属间化合物生成. NiTi形状记忆合金超声波焊缝呈可逆单相转变过程,接头强度达到母材的65%,断裂位置在母材区,断口形貌呈现韧性断裂特征. 超声波焊接方法将有效解决NiTi形状记忆合金采用传统熔焊方法时产生脆性金属间化合物的这一问题,为NiTi记忆合金的连接提供了新的解决途径.     

几种铝钢异种金属熔钎焊工艺的对比与分析

采用脉冲旁路耦合电弧MIG焊、CMT及激光焊方法实现铝/镀锌钢板搭接焊,对焊缝界面微观组织、形貌及元素成分进行了观察分析,并测试了其力学性能.结果表明,三种焊接方法均可以实现铝/镀锌钢板异种金属的优质连接,获得成形良好的焊缝,搭接接头的抗拉剪强度均可以达到铝合金母材的80%以上,拉伸试样断裂在焊缝铝合金母材热影响区.当母材热输入及工艺合适时,三种方法下搭接接头界面处均形成一主要成分为Fe₂Al₅和FeAl₃,平均厚度约为8 μm的金属间化合物,而且控制金属间化合物的生成是获得铝/钢焊接优质接头的关键.     

TiNi形状记忆合金精密脉冲电阻对焊接头相变温度的变化规律

通过示差热分析 (DSC)和X射线衍射等分析手段 ,研究了焊接热量、焊接压力、随机热处理等焊接参数以及焊后热循环对焊接接头相变温度的影响 ,并总结了其影响规律 :焊接热量和焊接压力对焊接接头相变温度的影响较小 ,As 和Af 区间基本保持不变 ;焊后随机热处理对焊接接头相变温度有一定的影响 ,As 和Af 均随热处理时间的增加而提高 ;焊后冷热循环对焊接接头的相变过程和相变温度具有重要的影响 ,因而实施焊后接头热循环工艺过程是必要的。     

7075/TC4异种金属CMT Advanced+P熔钎焊特性分析

基于CMT Advanced+P焊接方法,以ER5356铝合金焊丝对7075铝合金和TC4钛合金组成的搭接接头进行熔钎焊试验,并对接头进行微观组织及力学性能分析.结果表明,焊接接头主要由焊缝区、铝合金侧热影响区和钎焊界面区组成;焊缝区主要是等轴晶;铝合金侧热影响区的晶粒表现出轧制特性,并在晶界附近析出大量金属间化合物;...     

Friction welding of TiNi alloy to stainless steel using Ni interlayer

Abstract

Friction welding was carried out between TiNi alloy and austenitic stainless steel with and without a Ni interlayer. When TiNi alloy was welded to stainless steel without the Ni interlayer, a large amount of brittle Fe₂Ti intermetallic compound was formed at the weld interface. The formation of this brittle compound led to degradation of the joint strength. The Ni interlayer changed the microstructures at the weld interface and improved the joint strength. A fracture occurred at the interface between Ni and TiNi. The interface between Ni and TiNi was free from Fe₂Ti and consisted of mainly TiNi₃ and TiNi. After TiNi₃ was formed as the reaction layer, a eutectic reaction occurred between the TiNi₃ and TiNi base alloy. A reaction layer with a eutectic structure tends to form at the periphery, where the temperature would be higher than that of the central region.     

真空热循环作用下LF6合金焊接接头的拉伸性能和微观组织

采用精密多功能低温静载材料实验机、热循环试验装置、透射电镜和扫描电镜，系统研究了真空热循环条件下LF6合金焊接接头的拉伸性能和微观组织，分析讨论了真空热循环对LF6合金焊接接头的影响规律。研究结果表明，在循环300周次范围内，真空热循环可改善LF6合金焊接接头的拉伸性能，使其强度和塑性均得到提高。热循环对焊接接头拉伸性能具有影响，并同循环次数有关。初始循环时，由于位错不断增殖，使得LF6合金焊接接头的强度和塑性增加较快；经热循环70周次后，接头的强度和塑性均达到最高值；循环次数继续增加，强度和塑性开始下降，这可能与晶内位错密度降低、晶界处形成位错墙有关。     

Microstructures and mechanical properties of laser-welded TiNi shape memory alloy and stainless steel wires

The Nd:YAG laser welding was used to join the TiNi shape memory alloy and AISI304 stainless steel wires. The microstructural features of the dissimilar material joint were analyzed. The tensile and hardness tests were carried out to examine the mechanical properties and microhardness distribution of the welded joint. The results show that the joint has the non-homogeneous microstructure and element distribution. The brittle phases such as Fe2Ti, FeTi, Cr2Ti, Ti3Ni4, Fe0.2Ni4.8Ti5 and TiN mainly segregate in rich Ti region of fusion zone. The laser-welded joint has the tensile strength of 298 MPa with the elongation of 3.72% and exhibits the brittle fracture features on the fracture surfaces. The reasons for low joint strength were discussed in this investigation.     

Effect of gas flow rate on shapes of weld bead sections. Study on high‐speed surface treatment by arc with laser (2nd report)

Recently, lightening, speed-up and decreasing vibration of the transport vehicles have been discussed for improving of environmental problems. As one solution, the material hybrid concept using aluminum alloys and high strength steels has been proposed. Therefore, new welding processes by which these dissimilar materials can be joined in high reliability and productivity are demanded. Laser roll welding was developed for joining of dissimilar metals by M. Kutsuna, M. Rathod and A. Tsuboi in 2002. Up to now, a CO₂ laser has been used as a heat source. In the present work, laser roll welding of low carbon steel and aluminum alloy using a 2 kW fibre laser was investigated to improve the joint properties due to the effective heating characteristics. Effects of the process parameters were studied. Otherwise, the influences of process parameters on the weldability, the formation of intermetallic compound layer and the mechanical properties have been investigated. As a result, various types of intermetallic compound layer were confirmed at the laser roll welded joint interfaces. When intermetallic compound layer thickness was less than 10 μm, the specimen was a failure in the base metal of low carbon steel in the tensile shear test.     

基于试验设计与统计分析的双相钢激光焊工艺优化

为了优化激光焊接接头力学性能,利用试验设计方法对厚度为1.7 mm的DP600双相钢进行对接焊接试验,采用回归分析得到了激光焊接功率、焊接速度、离焦量、侧吹保护气体流量与接头抗拉强度之间的数学模型. 分析了焊接速度与侧吹气流量对焊缝抗拉强度的交互影响作用. 通过遗传算法优化该模型并得到了最优的焊接工艺参数组合,当焊接功率为1.7 kW,焊接速度为25 mm/s,侧吹气流量为2.4 m3/h,离焦量为-1 mm时焊缝的抗拉强度最大. 验证试验所测的焊缝抗拉强度值与模型预测值的相对误差在5%以内. 结果表明,文中研究可以有效的预测与优化厚度为1.7 mm的双相钢激光焊接质量.