异种金属扩散焊接接头的超声检测

异种金属扩散焊接接头存在多种类型的缺陷,这些缺陷严重影响焊接结构的完整性和零部件本身的使用性能。利用超声波扫描成像技术获得试样的扫描图样,然后从扩散焊接界面的显微结构和界面超声回波信号等角度,阐述了扩散焊接接头的原材料裂纹、接头裂纹、未焊合缺陷和焊接良好区域的特征。通过有效的无损检测手段,可以准确地评价缺陷的类型、大小和位置。     

扩散焊接头缺陷超声C扫描检测能力分析

扩散焊界面缺陷的检测是目前无损检测领域的难点之一. 为研究超声C扫描对钛合金扩散焊接头小缺陷的检测能力,以钛合金为研究对象,制作了含有不同尺寸和类型缺陷的扩散焊试件,研究了步进长度和检测频率对检测能力的影响,最后通过破坏性测试结果对其进行验证. 结果表明,使用较小的步进长度和较高的检测频率,可提高检测的准确度,但扩散焊界面存在大量接触型和微小型缺陷,因此采用超声法难以对其进行精确定量.     

铝基复合材料超声波辅助钎焊质量评价

根据铝基复合材料钎焊接头的结构特点,分析了界面的声学信号特征,并采用先进的超声成像法对接头质量进行了检测,同时获得了界面的A扫描信号、B扫描和C扫描图像.研究结果表明,结合A扫描信号、B扫描和C扫描图像的特征,能够判断缺陷类型及其位置,并通过断面金相分析进行了验证.超声成像技术能反映出铝基复合材料钎焊界面的接合状态,可检测出气孔、氧化膜夹杂和未钎透缺陷,为铝基复合材料钎焊的研究提供了有效的检测手段.     

导向环钎焊接头超声检测图像处理及质量评价

采用水浸聚焦超声C扫描成像方法对导向环钎焊接头进行了无损检测,针对超声检测图像特征,采用基于面积重构的形态学图像处理方法进行了缺陷分割.根据图像处理结果,计算了钎焊接头的焊合率以及最大缺陷的位置,实现了导向环钎焊质量的无损评价.利用Matlab语言的图形用户界面工具开发了导向环钎焊接头超声检测图像处理与质量评价软件,该软件界面简洁、易操作,并且能够脱离MATLAB语言环境独立运行,便于推广应用.     

铝合金微流道散热板真空扩散焊可靠性及气淬工艺

采用真空扩散焊对6063铝合金微流道散热板进行了连接。研究了6063铝合金扩散焊界面的组织形态及界面结合力,以及不同下压量(0. 2 mm,0. 5 mm,0. 7 mm)对扩散焊接头微观组织及力学性能的影响。同时,对扩散焊接头进行气淬处理,对比分析了气淬前后扩散焊接头组织与性能的差异。研究结果表明,扩散焊后流道侧壁呈现墩粗现象,下压量越大墩粗现象越明显。在扩散焊温度为520～540℃、保温时间为90 min、下压量为0. 5mm时,扩散焊界面可以获得均匀、连续、致密的组织,接头抗拉强度平均值高达84. 5 MPa,达到母材强度的90%以上。扩散焊接头经过气淬处理后,可以观察到大量细小分散的Mg2Si弥散强化相分布在基体组织中,洛氏硬度由78. 2 HRL提高到98. 6 HRL,接头抗拉强度达到186. 5 MPa。     

超声辅助铝/钛搅拌摩擦搭接接头的成形和组织

借助超声波辅助的方法对铝/钛异种合金进行搅拌摩擦搭接,研究超声波作用对接头的成形和组织的影响. 结果表明,当超声波施加在铝板时,接头的钩状缺陷较高,且会出现孔洞缺陷;当超声施加在钛板时,接头无缺陷. 超声振动能够增大铝/钛界面扩散层的厚度,对接头性能的提高起到一定的促进作用. 当搅拌头转速为300 r/min时,界面扩散层厚度较薄;当搅拌头转速升高至500 r/min时,界面生成一层厚度约为1 μm的金属间化合物. 超声辅助焊接可明显提高接头的断裂载荷.     

扩散焊工艺对6063铝合金焊接接头性能的影响

分别采用固相扩散焊和瞬间液相扩散焊方法焊接6063铝合金。采用金相显微镜对扩散界面附近的显微组织进行了分析;采用万能试验机测试了焊接接头的抗拉强度。试验结果表明,在连接同种铝合金材料的情况下,固相扩散焊相比瞬间液相扩散焊能够获得更为良好的接头性能。在焊接温度540℃、焊接压力8 MPa、保温时间80 min时,固相扩散焊接头区域成分均匀,没有空洞等缺陷,抗拉强度为122 MPa,达到同种热处理条件下母材抗拉强度(130 MPa)的94%。     

电子束焊-钎焊复合焊T形接头组织性能分析

实现了TA15钛合金T形接头的电子束焊-钎焊复合焊接.采用扫描电镜、能谱分析仪和X射线衍射分析仪等测试手段,对接头的微观组织形貌、元素成分分布和界面反应产物等进行分析研究.并分别对复合焊接头和电子束焊接头的弯曲性能进行了比较分析.结果表明,在适当的工艺条件下,可以实现TA15钛合金T形接头的电子束-钎焊复合焊接.在电子束焊缝和钎焊缝的界面处存在Cu,Ni元素的扩散和界面反应.复合焊接头的塑性要优于电子束焊,其所承受的最大压强略低于电子束焊.     

TiAl/40Cr扩散焊接头强度评价与预测

为了解决界面回波幅度均值无法评价异种材料扩散焊接头强度的问题,文中提出一种接头强度评价与预测方法.该方法基于二叉树支持向量机构建界面缺陷的识别模型,根据识别结果计算界面的焊合率,建立焊合率与抗剪强度的关系.采用线性拟合的方法获得抗剪强度的经验公式,用于预测接头强度.结果表明,构建的缺陷识别模型可以有效地识别出扩散焊界面未焊合、弱接合和微孔缺陷,焊合率与接头抗剪强度具有相关性,抗剪强度随着焊合率的增加而增加.实现了接头强度的预测,预测强度与实测值吻合较好.     

奥贝体钢轨和珠光体钢轨气压焊接头界面行为及力学性能分析

采用气压焊对U26Mn奥贝体钢轨和U75V珠光体钢轨混焊进行研究,通过OM、SEM、冲击、拉伸、硬度试验探究异种钢轨气压焊接头焊缝界面的冶金结合特征与力学性能水平。结果表明:气压焊接头焊缝界面两侧存在元素扩散行为,焊缝界面金属在热机循环作用下发生了交互结晶和再结晶,冶金结合良好(除轨底脚外);焊态接头平均强度达到贝氏体钢轨母材的86%,正火态接头平均强度达到贝氏体钢轨母材的90%;焊态接头轨顶面平均硬度、软化区平均硬度及宽度均满足TB/T1632《钢轨焊接》标准要求;接头中存在硫化物夹杂,对接头冲击韧性有较大影响。     

扩散连接接头质量评价现状

回顾扩散连接接头质量无损检测与评价的现状，介绍目前研究较多的超声反射法、超声信号处理、超声成像及实时监控等方法。由于扩散连接接头无损检测的复杂性，大多数检测技术还处于实验室研究阶段，因此，深入研究超声波与扩散连接界面的相互作用和先进的信号分析处理方法，对扩散连接接头质量的评价具有重要意义。     

UPA based 3D visualization of discontinuities in great thickness EBW seam

Electron beam welding(EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined.It is a complex high-temperature metallurgical process,and the quality of welding may deteriorate because of defects caused by improper welding parameters,especially in the EBW of thickened aluminum alloy plate.Ultrasonic phased array(UPA) technology has been applied more widely in the field of nondestructive testing because of its ability of effectively controlling the shape and direction of the emitted ultrasonic beam.In present research,a specimen with EBW seam on thickened aluminum plate was tested with a linear array ultrasonic phased array probe,and a large number of B-scan images of the weld were acquired by electronic scanning in probe combined with the mechanical scanning of the probe along the weld direction.This large number of B-scan images were stacked to construct the volume data,with which the 3D image of the weld discontinuities were reconstructed,and the 3D visualization was realized.More details about weld discontinuities' spatial distribution and orientation were revealed,and this approach also made the results of non-destructive ultrasonic testing more easily to understand.     

UPA based 3D visualization of discontinuities in great thickness EBW seam 1

Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined.It is a complex high-temperature metallurgical process,and the quality of welding may deteriorate because of defects caused by improper welding parameters,especially in the EBW of thickened aluminum alloy plate.Ultrasonic phased array(UPA) technology has been applied more widely in the field of nondestructive testing because of its ability of effectively controlling the shape and direction of the emitted ultrasonic beam.In present research,a specimen with EBW seam on thickened aluminum plate was tested with a linear array ultrasonic phased array probe,and a large number of B-scan images of the weld were acquired by electronic scanning in probe combined with the mechanical scanning of the probe along the weld direction.This large number of B-scan images were stacked to construct the volume data,with which the 3D image of the weld discontinuities were reconstructed,and the 3D visualization was realized.More details about weld discontinuities' spatial distribution and orientation were revealed,and this approach also made the results of non-destructive ultrasonic testing more easily to understand.     

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.     

Development of a bonding interface between steel/steel and steel/Ni by ultrasonic welding

Ultrasonic welding is a solid-state welding technique that can bond materials at a relatively low temperature and pressure. In this study, steel/steel and steel/Ni combinations were successfully bonded by ultrasonic welding, and the development of the bonding interface was examined. The bonding strength was obtained by a lap shear test and increased with welding time, as did the fraction of bonded area observed by SEM. The bonding process sequence was investigated by SEM and electron backscatter diffraction (EBSD) analysis of a cross-section at the bonding interface. It was revealed that abrasion is caused by oscillation to form small particles consisting of steel and Ni and that the particles are grown and subsequently flattened with welding time. Bonding is achieved by the flattened particles spreading along the bonding interface without any voids.     

A comparative evaluation of ultrasonic testing of AISI 316L welds made by shielded metal arc welding and gas tungsten arc welding processes

Ultrasonic testing of austenitic welds prepared by two different welding processes is studied in this paper. The two welding processes considered are shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) and the ultrasonic testing technique used is time-of-flight diffraction (ToFD). Identical artificial flaws were implanted in both welds during the welding process. Austenitic characteristics consisting of grain orientation distribution and anisotropy show that the GTAW specimen is more isotropic than the SMAW due to the orientation of its grains. Moreover, comparison of echo amplitudes shows higher attenuation for the weld prepared by the GTAW process. The specimens were examined by the ultrasonic ToFD technique under identical conditions. B-scan images obtained from ToFD measurements of the two welds indicate that inspection of the specimen prepared by the SMAW process is easier than the one made by the GTAW process due to higher scattering of waves in the latter. The measurements also showed that the probe positioning is very important in the detection of diffracted echoes when using the ToFD technique.     

引线键合中多向超声波能量传输特性研究

引线键合主要是采用超声波热键合技术，而超声波振动传播和能量传递是超声波键合设备中一个非常关键和复杂的问题。利用波在弹性体中传播的机理，给出超声波聚能杆和劈刀的振动传递特性，利用多普勒振动计PSV-300-F(1．5MHz)测量了振动位移和速度，证实了理论分析结果，并对双向垂直传输超声波能焊具的性能进行了研究，阐明垂直双向加载是一种高效的传能模型。     

Evolution of bonding interface during ultrasonic welding between steel and aluminium alloy

Ultrasonic welding (USW), a solid-state bonding technique, was applied to join ultra-low carbon steel and Al5052 aluminium alloy. The evolution of bonding strength and microstructure at the bonding interface during ultrasonic welding was investigated with an emphasis on the early stage before the formation of intermetallic compound. Initially, adhesive wear starts when steel and Al alloy have sliding contact, and thereafter, a thin layer of Al is attached onto the surface of the steel while the wear of Al base metal is continued owing to the sliding. As the welding time increases, bonding sections are gradually formed with the increase of interfacial temperature owing to the sliding friction, whose process is illustrated in this article.     

Microstructure and microtexture evolution of aluminum alloy 3003 under ultrasonic welding process for embedding SiC fibre

Ultrasonic welding process can be used for bonding metal foils which is the fundament of ultrasonic consolidation (UC).UC process can be used to embed reinforcement fibres such as SiC fibres within an aluminum matrix materials.In this research we are investigating the phenomena occurring in the microstructure of the parts during ultrasonic welding process to obtain better understanding about how and why the process works.High-resolution electron backscatter diffraction (EBSD) is used to study the effects of the vibration on the evolution of microstructure in AA3003.The inverse pole figures (IPF) and the correlated misorientation angle distribution of the mentioned samples are obtained.The characteristics of the crystallographic orientation,the grain structure and the grain boundary are analyzed to find the effect of ultrasonic vibration on the microstructure and microtexture of the bond.The ultrasonic vibration will lead to exceptional refinement of grains to a micron level along the bond area and affect the crystallographic orientation.Ultrasonic vibration results in a very weak texture.Plastic flow occurs in the grain after welding process and there is additional plastic flow around the fibre which leads to the fibre embedding.