TiNbTaZr难熔高熵合金/W真空扩散焊组织及性能

TiNbTaZr难熔高熵合金和钨在不同温度下进行真空扩散焊,采用SEM、TEM、XRD和万能试验机等手段研究了各参数下接头界面的微观组织演变、元素扩散行为和力学性能。结果表明,各参数下两种材料均实现了良好连接。接头界面靠近基体两侧组织形成两类反应层,其中TiNbTaZr侧生成富Ta(Nb、W) BCC相和富Zr BCC相,钨侧为单相。元素扩散层宽度随温度升高而增大,最宽达52.77μm。接头剪切强度随温度升高而增加,最高为155 MPa。断裂机制为脆性断裂,接头均在钨侧反应层断裂。     

(CoCrFeNi)100-xCux中间层对WC-10%Co硬质合金与42CrMo钢快速扩散连接的影响

本文将不同Cu含量的(CoCrFeNi)_100-xCu_x高熵合金(x=10、20、30、40、50)作为中间层,利用放电等离子烧结对WC-10%Co(质量分数)硬质合金和42CrMo钢进行固相扩散焊,探究了高熵合金中间层成分对焊接接头界面组织特征、元素扩散行为及最终力学性能的影响。结果显示,各成分下硬质合金与高熵合金界面均无明显微孔和微裂纹,但高熵合金中间层与42CrMo钢界面普遍存在少量微孔,且低Cu含量(CoCrFeNi)90Cu10与42CrMo钢界面存在大量微孔和微裂纹。扩散焊后中间层出现了富Cu相和富Cr相,其中富Cu相在Cu的原子数分数减小到10%后基本消失,而富Cr相主要分布在界面附近,且Cu的原子数分数增加到50%时主要分布在贫Cu相边缘及内部。中间层元素(Co、Cr、Fe、Ni)在硬质合金中的扩散距离比硬质合金中W元素在中间层的扩散距离要远。相较而言,高熵合金中间层各元素与42CrMo钢之间的元素扩散距离基本相同。另外,在使用(CoCrFeNi)_100-xCu_x高熵合金作为中间层时...     

高熵合金CoCrFeMnNi/不锈钢真空扩散焊

采用真空扩散焊方法实现了CoCrFeMnNi高熵合金与304不锈钢在900℃~1000℃下的稳固连接。利用扫描电镜、EDS能谱分析、显微硬度测试和拉伸试验机研究扩散焊温度对原子界面行为和接头机械性能的影响规律。结果表明,温度较低时,界面上存在大量的孔洞,随着温度的升高,孔洞逐渐消失。结合EDS能谱分析和硬度测试结果可知,反应层成分为FCC固溶体,没有金属间化合物产生。所有接头拉伸后断裂均发生在远离界面的高熵合金一侧,随着扩散焊温度的升高,抗拉强度略微升高,应变明显增大,这可能与第二相的数量有关,1000℃时接头的抗拉强度和应变均达到最大值,分别为585MPa和50%。     

CoCrFeMnNi高熵合金作为中间层的Cu/304不锈钢扩散连接研究

将CoCrFeMnNi高熵合金作为中间层,采用真空固态扩散方法实现Cu/304不锈钢的连接,通过SEM、EDS以及显微硬度测试,研究温度对扩散反应机理及性能的影响,采用Fick第二定律计算Cu/Fe原子在高熵合金中的扩散系数,借助XRD以及高熵合金中固溶体相形成判据分析扩散界面的相组成。结果表明:在800～900℃下,高熵合金与Cu和304不锈钢分别实现了稳固连接,界面处发生了元素的互扩散,随着温度的升高,Cu/Fe在高熵合金中的平均扩散系数增加;Cu/CoCrFeMnNi高熵合金和CoCrFeMnNi高熵合金/304不锈钢扩散界面处均未形成脆性金属间化合物;扩散界面处硬度呈连续变化趋势。研究表明,CoCrFeMnNi高熵合金是一种可用于Cu/304不锈钢异种材料扩散连接的阻挡层材料。     

Cu和Ni原子在高熵合金CuCoCrFeNi中的扩散行为

研究了CuCoCrFeNi高熵合金在镀镍和镀铜并经不同温度退火不同时间后扩散层的显微组织、成分以及扩散层厚度。结果表明,Cu原子在CuCoCrFeNi高熵合金中不易发生晶格扩散,但经高温或长时间热处理后,Cu原子可在晶界处发生扩散。Ni原子与高熵合金中的组元发生了明显的互扩散;Cu和Ni原子在高熵合金中的扩散是空位机制,只有"适配空位"才能为原子在高熵合金中提供迁移的位置。显微硬度测试结果表明,Cu/高熵合金界面处显微硬度较低,而Ni/高熵合金界面处显微硬度逐渐提高。     

Cu/W-Ni/Ni多中间层的钨/钢扩散连接(英文)

采用铜箔/90W-10Ni(质量分数)混合粉末/镍箔多中间层,在加压5 MPa、连接温度1150°C、保温60 min的工艺条件下,对纯钨(W)和0Cr13Al铁素体不锈钢进行真空扩散连接。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合金层/W-Ni复合材料层/镍层/钢母材五部分组成。接头中的W-Ni复合材料层由90W-10Ni混合粉末固相烧结而生成,其组织均匀、致密。W-Ni复合材料层与钨母材以瞬间液相扩散连接机制来实现良好结合。接头剪切强度达到256 MPa,断裂均发生在W-Ni复合材料层与镍层的结合区域,断口形貌呈现为韧性断裂。经过60次700°C至室温的水淬热震测试,接头无裂纹出现。     

Al/Co相界面的扩散溶解层

采用镶嵌式扩散偶,在不同退火处理条件下,对Al/Co扩散溶解层进行了研究。利用扫描电子显微镜和电子探针显微分析仪观察和分析了扩散溶解层的形态和形成规律,并对其形成机理进行了探讨。结果表明,当进行600℃保温75h退火处理后,在Al/Co界面处形成了结构为Al/Co2Al9/Co4Al13/Co2Al5/CoAl/Co,并与Al-Co二元合金相图上相的位置顺序一致、厚度约170μm的扩散溶解层。CoAl相层首先在Co基体上形成,然后其余三个相层都在CoAl相层上形成;Co4Al13相层和Co2Al5相层几乎同时呈"柱状"方式分别纵向向Co块和Al丝相向生长,生长到一定的厚度,再从根部转向横向生长,最终层2和层3交错在一起;最后Co2Al9相层在Al/Co4Al13界面处形成。Al-Co扩散溶解层的形成是Al和Co固相扩散、溶解与结晶的结果,由于扩散浓度和固溶度的相互作用,导致了扩散溶解层析出的序列性。     

TiAl/Ti/Nb/GH99扩散连接接头的界面组织结构及接头强度

采用Ti/Nb复合中间层对TiAl与镍基高温合金(GH99)进行扩散连接.采用扫描电镜、电子探针和X射线衍射等手段对连接接头的生成相及界面组织结构进行分析,采用抗剪强度测试对接头的连接强度进行评价.结果表明,GH99/Nb/Ti/TiAl的典型界面结构为GH99/(Ni,Cr)ss/Ni3Nb/Ni6Nb7/Nb/(Ti,Nb)ss/α-Ti+(Ti,Nb)ss/Ti3Al/TiAl.当连接温度为900℃,连接时间为30 min,连接压力为20 MPa时,所得接头抗剪强度最高为273.8 MPa.随着连接温度的升高,界面组织结构及反应层厚度发生变化.当连接温度T>900℃时,界面处生成对接头强度有不利影响的Ni6Nb7反应层;根据试验结果,进一步分析了各反应层的形成过程,揭示了GH99/Nb和Nb/Ti/TiAl的界面扩散反应机制.     

形变+退火对CoCrCuFeNi高熵合金显微组织及性能的影响

对高熵合金CoCrCuFeNi进行30%形变及退火处理,分析了合金的点阵结构和晶粒形貌变化,并进行了硬度测试。结果表明,CoCrCuFeNi合金的部分树枝晶在冷形变后发生弯曲,硬度提高;退火后合金晶粒部分二次枝晶臂消失,硬度明显降低;高熵合金CoCrCuFeNi形变后退火在一定程度上促进了富铜相的溶解和原子的扩散。     

镀Ni层对钛/钢钎焊接头原子扩散行为的影响机制

针对钛/钢钎焊接头金属间化合物引起的焊缝组织性能恶化问题,通过对比试验,研究了母材匹配面镀Ni层对接头原子扩散行为、微观组织和力学性能的影响机制。结果表明:Ni层对Fe、Ti等元素扩散的阻碍作用程度上存在差异,这种差异性与Ni层在接头区域中的介入位置相关。Ni层阻碍作用改变了Fe、Ti等元素在接头各区域的原子浓度分布,减缓了原子之间的冶金反应程度,降低了脆性金属间化合物的生成量。Ni层的介入可使接头微观组织和力学性能得到有效改善。     

Diffusion brazing repair of IN738 superalloy with crack-like defect: microstructure and tensile properties at high temperatures

In this study, tapered slots with an opening width about 200?μm were artificially fabricated in IN738LC superalloy to imitate service cracks. The ‘cracks’ were repaired by diffusion brazing with a Ni–Cr–Co–Al–Ta–B filler alloy at 1150°C and then heat treated at 1180°C (HT-A) and 1190°C (HT-B), respectively. A joint with uniform microstructure, chemical composition and hardness was obtained using HT-B. The mechanisms of the borides evolution during homogenisation were discussed. The tensile strength of the HT-B joint tested at 20, 600 and 800°C reached up to approximately 96, 90 and 87% of the base metal, respectively. The fracture modes of the joints tensile tested at various temperatures were discussed.     

Direct active soldering of Al0.3CrFe1.5MnNi0.5 high entropy alloy to 6061-Al using Sn-Ag-Ti active solder

Al_0.3CrFe_1.5MnNi_0.5 high entropy alloys (HEA) have special properties. The microstructures and shear strengths of HEA/HEA and HEA/6061-Al joints were determined after direct active soldering (DAS) in air with Sn3.5Ag4Ti active filler at 250 °C for 60 s. The results showed that the diffusion of all alloying elements of the HEA alloy was sluggish in the joint area. The joint strengths of HEA/HEA and HEA/6061-Al samples, as analyzed by shear testing, were (14.20±1.63) and (15.70±1.35) MPa, respectively. Observation of the fracture section showed that the HEA/6061-Al soldered joints presented obvious semi-brittle fracture characteristics.     

The effects of ultrasonic nanocrystal surface modification (UNSM) on pack aluminizing for the fabrication of Pt-modified aluminide coatings at low temperatures

An 8–9 μm thick Pt layer was coated on a superalloy and transformed to a Ni–Pt alloy layer by the interdiffusion of Ni and Pt at 1050 °C for 3 h. The surface of the Ni–Pt alloy layer was pack aluminized to form a Pt-modified aluminide coating. Ultrasonic nanocrystal surface modification (UNSM) was applied to the alloy layer prior to pack aluminizing. The effects of UNSM on Pt-modified aluminide coatings fabricated at 750, 850, 950, and 1050 °C were studied. The treated Ni–Pt alloy layers had finer grain sizes than the untreated specimens. In addition, UNSM made the grain size of the Ni–Pt alloy finer and reduced the surface roughness. During pack aluminizing, the Pt-modified aluminide coatings fabricated following UNSM uptook more Al and were thicker than the untreated Pt-modified aluminide coatings at the various temperatures (750, 850, 950, and 1050 °C). The untreated Pt-modified aluminide coatings with pack aluminizing performed at 750 and 850 °C were composed of only a two-phase (NiAl + PtAl₂) layer, due to insufficient diffusion of Pt at the lower temperatures. However, two-phase and one-phase (NiAl) layers were obtained in the treated Pt-modified aluminide coatings which were pack-aluminized at 750, 850, 950, and 1050 °C, due to the diffusion of Pt through the greater amount of grain boundaries and increased volume generated by UNSM before the pack aluminizing. Additionally, the treated coatings had smoother surfaces even after the pack aluminizing. During cyclic oxidation at 1150 °C for 1000 h, the treated Pt-modified aluminide coatings aluminized at relatively low temperatures (750 and 850 °C) showed better cyclic oxidation resistance than the untreated Pt-modified aluminide coating aluminized at 1050 °C.     

Ti-37.5Zr-15Cu-10Ni钎焊钼的钎缝组织分析

采用Ti-37.5Zr-15Cu-10Ni非晶钎料真空钎焊钼,获得Mo/Mo钎焊接头,研究钎焊过程液态钎料与母材的相互作用. 结果表明,液态Ti-37.5Zr-15Cu-10Ni钎料与钼发生扩散–溶解,即母材钼向钎料中的溶解和钎料组分向母材的扩散. 随钎焊温度的升高,钼向钎料中溶解量增加,凝固后钼主要固溶在Ti基固溶体内;随钎焊温度的升高,发生钎料组分向母材晶间的扩散,当温度为900 ℃时,发生显著的晶间渗入现象. 为得到良好的钎焊接头,避免母材过量溶解和晶间渗入的发生,Ti-37.5Zr-15Cu-10Ni钎料真空钎焊钼温度不宜高于900 ℃.     

Vacuum brazing of TiAl-based intermetallics with Ti–Zr–Cu–Ni–Co amorphous alloy as filler metal

An amorphous Ti41.7–Zr26.7–Cu14.7–Ni13.8–Co3.1 (wt%) ribbon fabricated by melt spinning was used as filler to vacuum braze Ti–48Al–2Nb–2Cr (at%) intermetallics. The influences of brazing temperature and time on the microstructure and strength of the joints were investigated. It is found that intermetallic phases of Ti₃Al and γ-Ti₂Cu/Ti₂Ni form in the brazed joints. The tensile strength of the joint first increases and then decreases with the increase of the brazing temperature in the range of 900–1050 °C and the brazing time varying from 3 to 15 min. The maximum tensile strength at room temperature is 316 MPa when the joint is brazed at 950 °C for 5 min. Cleavage facets are widely observed on all of the fracture surfaces of the brazed joints. The fracture path varies with the brazing condition and cracks prefer to initiate at locations with relatively high content of γ-Ti₂Cu/Ti₂Ni phases and propagate through them.     

采用两种银基活性钎料钎焊AlN陶瓷与可伐合金的接头组织与性能

采用Ag-Cu-Ti和Ag-Cu-In-Ti两种活性钎料箔带,分别在860℃/10 min和760℃/10 min两种规范下对AlN与可伐合金(4J29)进行了真空钎焊连接,获得了冶金质量良好的接头. 对接头室温抗剪强度进行了测试,AlN/Ag-Cu-Ti/4J29和AlN/Ag-Cu-In-Ti/4J29两种接头强度分别为126和113 MPa. 微观分析结果表明,两种接头中靠近陶瓷母材附近生成了连续的扩散反应层,结合XRD结果,该层主要由TiN相组成,反应层的厚度对接头强度有影响;钎缝基体区由铜基固溶体、银基固溶体和复杂的Ni(Fe,Co)-Ti化合物组成.     

Diffusion parameters of grain-growth inhibitors in WC based hardmetals with Co,Fe/Ni and Fe/Co/Ni binder alloys

The diffusion behaviour of the grain-growth inhibitors (GGI) Cr and V during early sintering stages from 950 to 1150 °C was investigated by means of diffusion couples of the type WC-GGI-binder/WC-binder. Besides Co, also alternative Fe/Ni and Fe/Co/Ni binder alloys were investigated. It was found that the diffusion in green bodies differs significantly from sintered hardmetals. Diffusivities in the binder phase were determined from diffusion couples prepared from model alloys and were found to be almost equal for Co and alternative binder alloys. The diffusion parameters determined from green bodies allowed to estimate the GGI distribution in a hardmetal during heat up. This was subsequently used to estimate an appropriate grain size of VC and Cr₃C₂ in hardmetals, which is required to ensure a sufficient GGI distribution during sintering before WC grain-growth initiates.     

Oxidation von Schweißverbindungen austenitischer Stähle bei hohen Temperaturen

Oxidation of austenitic steel welds at elevated temperatures Two steels (18–21 Cr, 8–11 Ni and 17–20 Cr, 7–10 Ni) welded with filler material of the composition 18 Cr, 11 Ni, have been studied with respect to their resistance to oxidizing atmospheres in the temperature range between 850 and 1000°C, test durations being up to 5000 h. The behaviour has been evaluated in terms of scale properties (compactness, adhesion), structural stability (by metallographic methods), scale composition (with the micro analizer) and investigation of diffusion from the base metal. On the basis of the results obtained it may be concluded that the base metal could be exposed to a maximum temperature of 900°C, while the welded zone is not sufficiently resistant at that temperature; consequently, the service temperature should be limited to a maximum of 850°C.     

Diffusion Bonding of Stainless Steel to Copper with Tin Bronze and Gold Interlayers

Vacuum diffusion bonding of stainless steel to copper was carried out at a temperature ranging from 830 to 950 °C under an axial pressure of 3 MPa for 60 min with three kinds of interlayer metals: tin-bronze (TB) foil, Au foil, and TB-Au composite interlayer. The results showed that the grain boundary wetting was formed within the steel adjacent to the interface due to the contact melting between TB and Au when TB-Au composite interlayer was used. The grain boundary wetting could occur at a relatively low temperature of 830 °C and becomes significant with the increase of temperature. The tensile strength of the joint with TB-Au was higher than that with TB or Au interlayer separately and could be 228 MPa at the joining temperature of 850 °C. Furthermore, the axial compression ratio of the specimen joined at 850 °C was approximately 1.2%. Therefore, a reliable and precise joining of stainless steel to copper could be realized by diffusion bonding with the TB-Au composite interlayer at a comparatively low temperature.     

有机溶剂保护对Al/Ni扩散连接的影响规律研究

采用有机溶剂保护实现了纯铝和纯镍的扩散连接。利用扫描电子显微镜、能谱分析以及X射线衍射等分析手段,确定了Al/Ni扩散连接接头典型的界面结构为Al/Al_3Ni_2/Ni。在扩散连接过程中利用有机溶剂防止铝表面发生二次氧化,相比直接扩散连接可得到更好的焊接质量。研究了连接温度对Al/Ni接头界面结构的影响规律,随着连接温度的升高各反应层厚度逐渐增加。当连接温度为490℃,连接时间为60 min,连接压力为2 MPa时,接头抗剪强度达到最大值,为17.83 MPa,比该工艺下直接扩散连接得到的焊接接头强度提高了约55%。