Diffusion Bonding of TiAl to Ti6Al4V Using Nanolayers

Microstructural characterization of TiAl to Ti6Al4V dissimilar diffusion bonds assisted by reactive Ni/Al nanolayers was performed in this study. The nanolayers (alternated Al and Ni) were deposited onto the base material surfaces. Diffusion bonding was performed at 700 and 800 °C under pressures from 5 to 40 MPa and dwell times between 60 and 180 min. Microstructural characterization was performed using high-resolution transmission and scanning electron microscopies. The observations revealed that dissimilar TiAl to Ti6Al4V joints assisted by Ni/Al reactive nanolayers can be obtained successfully at 800 °C during 60 min using a pressure of 20 MPa. The bond interface is thin (less than 10 µm) and is mainly composed of NiAl grains. Thin layers of Al-Ni-Ti intermetallic compounds were formed adjacent to the base materials.     

In Situ Characterization of NiTi/Ti6Al4V Joints During Reaction-Assisted Diffusion Bonding Using Ni/Ti Multilayers

Reaction-assisted diffusion bonding process of NiTi and Ti6Al4V was studied in situ. For this purpose, experiments were carried out at the High Energy Materials Science beamline (P-07) at PETRA-III (DESY). Ni/Ti multilayer thin films 2.5 μm thick with 12 and 25 nm modulation periods were directly deposited by magnetron sputtering onto the materials being joined. The NiTi and Ti6Al4V coated parts were placed with the films facing each other in a dilatometer equipped with Kapton windows for the x-ray beams. Microjoining was promoted by applying a 10 MPa pressure and inductively heating the materials, while simultaneously acquiring x-ray diffraction scans across the bond interface. Sound joints were produced at 750 °C. The formation of the NiTi₂ phase could not be avoided.     

SiC/TiAl扩散连接接头的界面结构及连接强度

对常压烧结的ＳｉＣ陶瓷与ＴｉＡｌ金属间化合物进行了真空扩散连接。采用扫描电镜、电子和Ｘ射线衍射分析等确定了反应产物的种类和接头的界面结构,并用拉剪试验评价了接头的连接强度。研究结果表明：ＳｉＣ与ＴｉＡｌ扩散连接中生成了ＴｉＡｌ２、ＴｉＣ和Ｔ５Ｓｉ３Ｃｘ三种上,接头的界面结构为ＳｉＣ／ＴｉＣ／（ＴｉＣ＋Ｔｉ５Ｓｉ３Ｃｘ）／ＴｉＡｌ。在１５７３Ｋ和１．８ｋｓ的连接条件下,接头室温剪强度达到２４０ＭＰａ     

Characterization of Al/Ni Nanoscale Multilayer Used for Transient-Liquid-Phase Bonding of Copper and Al2O3 Ceramic

研究制备系列具有不同调制周期的Al-Ni多层膜,并将其应用于铜与氧化铝陶瓷件的TLP(transient-liquid-phase,瞬间液相)连接。分别对制备的系列多层膜及金属陶瓷接头微观组织进行表征,同时采用DSC及XRD对反应多层膜反应特性进行研究。研究结果表明,采用Al/Ni微纳尺度多层膜不仅可降低铜与氧化铝连接温度,并能提高焊接接头质量。     

Effect of Stand-Off Distance on the Microstructure and Mechanical Properties of Ni/Al/Ni Laminates Prepared by Explosive Bonding

Ni/Al laminates are of great interest in many aerospace and military applications due to their excellent mechanical properties. However, their application has been limited in part due to challenges related to fabricating complex geometries. However, explosive welding is regarded as a promising technique to fabricate laminates. However, it is difficult to fabricate Ni/Al/Ni laminates with high interfacial shear strength and ductility if the stand-off distance has not been optimized during the explosion process. The goal of this study was to investigate the effect of stand-off distance on the microstructure and mechanical properties of Ni/Al/Ni laminates, and SEM and EDS were used to characterize the morphology and element distribution of the double layer interface. Tensile and tensile-shear tests were conducted to evaluate the mechanical properties of the laminates. The results indicated that with the increase in stand-off distance, three different kinds of interface were obtained (straight, wavy and continuously melted). Thickness of atomic diffusion layer increased with the increase in stand-off distance. Moreover, the Ni/Al/Ni laminates with wavy interface possessed highest value of ductility and interfacial bonding strength.     

连接温度对高铌TiAl合金扩散接头组织和强度的影响

在连接工艺参数为1000～1200℃/25MPa/90min条件下,对高铌TiAl合金(TAN)进行直接扩散连接。采用SEM、EDS、XRD和EBSD等方法对连接界面微观组织进行分析,并研究了连接温度对接头界面结构和剪切强度的影响。结果表明:当连接温度T1100℃时,连接界面清晰垂直,继续升高温度,界面消失;扩散连接过程中,连接界面处出现再结晶现象,随着连接温度的升高,再结晶晶粒不断增多并长大,并且再结晶区域出现大量α_2相;当连接温度达到1150℃时,接头平均抗剪强度达到最大值为105 MPa。     

冷轧Ti/Al层状复合材料固-液反应过程中的界面微观组织演变

将冷轧Ti/Al层状复合材料在675~750 ℃下进行不同时间的退火处理,退火过程中钛和铝都保持过剩,研究了Ti/Al层状复合材料的界面微观组织演变。结果表明：Ti和Al的界面层由2个亚层组成,其中一个为紧密的TiAl₃亚层,其微观结构为紧密的TiAl₃层,其中分布着随机取向的充满Al的裂纹,另一个为颗粒状的TiAl₃亚层,其微观组织结构是颗粒状的TiAl₃分布在Al基体中。在不同的退火温度和时间条件下,紧密TiAl₃亚层的厚度几乎没有变化,但是颗粒状亚层的厚度随着退火温度及时间的增加而增加;另外,界面层中的TiAl₃颗粒的体积分数在不同的温度下均随着退火时间的延长而下降。因此提出了反应扩散模型来描述界面层的形成机理,在此模型中,TiAl₃相是化学反应和扩散的结果,并且也考虑了TiAl₃相的溶解。计算结果表明TiAl₃相的形成与生长由化学反应控制,其等效厚度与退火时间之间遵循线性规律,这主要是因为Ti和Al原子能够快速地通过紧密的薄TiAl₃亚层。     

Cu/W-Ni-Co/Ni多中间层的钨/钢扩散连接

采用铜箔/90W-5Ni-5Co(质量分数,%)混合粉末/镍箔复合中间层,在加压5 MPa、连接温度1120℃、保温60 min的工艺条件下,对纯钨(W)和0Cr13Al钢进行了连接。利用SEM、EDS、电子万能试验机及水淬热震实验等手段研究了接头的微观组织、成分分布、断口特征、力学性能及抗热震性能。结果表明,连接接头由钨母材、Cu-Ni-Co合金层、钨基高密度合金层、镍层、钢母材5部分组成。接头中的钨基高密度合金层由90W-5Ni-5Co混合粉末固相烧结生成,其Ni-Co粘结相和钨颗粒相冶金结合且分布均匀。钨基高密度合金层与钨母材以瞬间液相扩散连接机制实现了良好结合。接头剪切强度达到286 MPa,断裂均发生在钨基高密度合金层/镍层结合区域,断口形貌呈现为韧性断裂。经过60次700℃至室温的水淬热震测试,接头无裂纹出现。     

Solid-State Diffusion Bonding of Nb_(SS)/Nb_5Si_3 Composite Using Ni/Al and Ti/Al Nanolayers

Diffusion bonding of refractory Nb–Si-based alloy was performed with Ni/Al and Ti/Al nanolayers under the condition of 1473 K/30 MPa/60 min. The Nb_(SS)/Nb_5Si_3 in situ composite with the nominal composition of Nb–22 Ti–16 Si–3 Cr–3 Al–2 Hf was used as the parent material. The joint microstructures were examined by using a scanning electron microscope equipped with an X-ray energy dispersive spectrometer. Shear test was conducted for the bonded joints at room temperature.Within the joint bonded with Ni/Al multilayer, element diffusion occurred between the base metal and the nanolayer, with the reaction products of AlNb_2 + Ni_3 Al, NiAl and AlNi_2 Ti phases. The average shear strength was 182 MPa. While using Ti/Al multilayer, the interface mainly consisted of TiAl,(Ti,Nb)Al and(Ti,Nb)_2 Al phases, and the corresponding joints exhibited an increased strength of 228 MPa. In this case, the fracture mainly took place in the TiAl phase and presented a typical brittle characteristic.     

AZ31B/Al电场固相扩散界面结构及性能分析

采用电场激活固相连接工艺(FADB)实现了AZ31B镁合金与铝粉的固相扩散,观察研究了界面处扩散溶解层的微观形貌和相组成以及界面处元素交互扩散分布情况,测试了扩散溶解层的表面硬度和耐腐蚀性,探讨电场对AZ31B/Al固相扩散的影响.研究结果表明,在FADB条件下,AZ31B/Al结合界面处形成的扩散溶解层由均匀共晶层-溶解过渡层和胞晶区构成;外加电场通过降低界面处生成物的激活能,促进了Mg-Al间的扩散反应,所形成的锯齿状结构有利于提高界面连接强度;试样表面的平均硬度及耐腐蚀性能均高于镁合金母材.     

反应等离子喷涂Ni3Al涂层的组织与性能

为了满足高温热防护的需求,采用等离子喷涂技术制备Ni3Al复合涂层,并详细研究了涂层的组织结构、结合强度、热震性能及高温抗氧化性能。结果表明,由于Ni、Al粉体之间接触充分,喷涂过程中,完全反应生成了Ni3Al中间相,并放出大量的热,涂层与基体呈微冶金结合,结合强度较普通镍包铝涂层高30%~40%,并具有良好的抗热震性和高温抗氧化性能     

93W/Ni/Mo1接头的等离子活化扩散焊接研究

利用等离子活化技术对93W/Ni/Mo1进行真空扩散焊接,用剪切强度和显微硬度表征焊接接头的力学性能,对焊接界面和接头断口物相及微观结构进行表征分析。结果表明,焊接温度低于800℃时,焊接界面有孔洞,焊接温度高于800℃时,焊接界面良好。焊接接头的剪切强度随着焊接温度的升高先升高后降低,在焊接温度为800℃时接头强度最大为100.2 MPa。焊接温度低于800℃时,焊接界面发生扩散形成固溶体;焊接温度高于800℃时,Ni/Mo1界面生成MoNi高硬度金属间化合物,降低焊接接头结合强度。93W/Ni/Mo1焊接接头的断裂破坏主要发生在Ni/Mo1扩散界面。     

Ti/Ni多层复合材料界面扩散行为的研究

本文针对累积叠轧5道次制备的Ti/Ni多层结构复合材料试样进行热处理,采用光学显微镜和扫描电镜分析方法,对复合材料的显微组织、界面结构和扩散反应层厚度等进行观察分析,结合动力学理论研究了Ti/Ni界面的扩散行为。研究结果表明：试样经过累积叠轧5道次轧制后,Ti/Ni界面未发生扩散;在(550 ℃-750 ℃)×(0.5 h-8 h)热处理后,Ti/Ni界面发生扩散,扩散层厚度与保温时间呈幂函数关系,与加热温度呈指数关系;随着热处理温度的升高,Ti-Ni扩散层的生长方式由650 ℃以下的体扩散控制逐渐转变为晶界扩散控制。通过计算和验证得到采用累积叠轧5道次制备的Ti/Ni多层复合材料的Ti/Ni界面固相反应层生长动力学方程为：y=1.7043*104*exp(-78202/RT) *t1.2009-0.0008T。     

CuNi复合中间层对Mg/Al扩散焊接接头组织及力学性能的影响

采用真空扩散焊接的方法获得了Mg/CuNi/Al扩散焊接接头。采用万能试验机测试焊接接头剪切强度,通过SEM,EPMA,XRD对焊接接头的显微结构和物相组成进行了分析。结果表明,Mg/CuNi/Al扩散焊接接头剪切强度随焊接温度和保温时间的增加先增加后减小,焊接温度440℃,保温时间90 min时,接头剪切强度最大值达到22.4 MPa。焊接接头主要由Al3Mg2致密组织层、Al12Mg17针状组织层、Al12Mg17和α-Mg网状组织层组成,Cu、Ni富集于网状组织层中。Mg/CuNi/Al扩散焊接接头断口主要由Al3Mg2、Al12Mg17、AlCu3、Al2Cu和Al7Cu23Ni化合物组成,断裂方式以脆性断裂为主。     

自生Ti2AlC/TiAl复合材料的组织及反应过程

采用自蔓延燃烧合成及真空电弧熔炼的方法,以碳纤维(Cf)、钛粉及铝粉为原料,合成了Ti2AlC/TiAl复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析了复合材料的物相组成和微观结构,讨论了原位合成Ti2AlC的反应和二次Ti2AlC的析出过程。结果表明,复合材料铸锭由Ti2AlC、TiAl和Ti3Al3相组成,基体由α2(Ti3Al)+γ(TiAl)片层和γ(TiAl)等轴晶粒构成,原位自生的Ti2AlC分布均匀,呈短纤维状或颗粒状。1200℃均匀化热处理促使Ti3Al分解为TiAl和Ti2AlC,导致Ti2AlC粗化,同时基体表面析出细小的二次Ti2AlC颗粒。     

Cu/Ni固相扩散界面的研究

采用彩色金相技术对“嵌入式”Cu/Ni扩散偶真空扩散处理时的界面迁移现象进行了观测,并研究了Cu/Ni界面间的扩散行为。结果表明,扩散偶在退火温度1123~1223K、保温时间25~150h(0·9×105~5·4×105s)的工艺条件下反应,Cu/Ni界面间结构由α/β转变为α/α′/β,其中α′为扩散层,实质是成分不均匀的固溶体,Cu/Ni界面间扩散行为是Kirkendall效应的一种显现,即界面上Cu和Ni元素均发生了扩散,但主要是Cu原子向Ni层的扩散。最后在试验数据基础上发现,扩散层厚度L与退火时间t之间满足抛物线L=K(t/t)n关系。     

加载方式对Cu/Al真空扩散连接的影响

采用恒压和脉冲加压两种加压方式下的真空扩散连接工艺对Cu/Al异种材料进行连接,利用扫描电镜和EDS对焊接接头的微观组织及元素扩散行为进行了研究.在焊接温度为540℃、扩散时间为60 min、焊接压力为2～5MPa的工艺下,焊接接头最高抗拉强度为197MPa.     

扩散时间对Al/Cu真空扩散连接的影响

采用真空扩散焊工艺对Al/Cu异种材料进行连接,研究了保温时间对接头微观组织及力学性能的影响.利用扫描电镜和EDS对焊接接头的微观组织及元素扩散行为进行了研究.结果表明:随着扩散时间的延长,接头的抗拉强度随之升高,焊接接头最高抗拉强度为185 MPa.     

Ni/Al Multilayers Produced by Accumulative Roll Bonding and Sputtering

Journal of Materials Engineering and Performance - Ni/Al multilayers are known to transform into NiAl in a highly exothermic and self-sustaining reaction. The fact that this reaction has a high...