TLP扩散焊过程中近表面区域元素贫化控制研究

为了控制TLP扩散焊过程中近表面区域元素贫化,通过对IC10合金TLP扩散焊不同充氩分压量实验,测试分析充氩分压对表面Cr元素含量的影响和对焊接组织性能的影响。实验结果表明:TLP扩散焊真空充氩分压能控制表面Cr元素贫化层厚度在4μm左右,能有效控制TLP扩散焊过程中的表面元素贫化问题;焊接保温20min后开始分压,对焊接接头组织性能无不利影响;焊后进行热处理,能提高焊接强度,恢复基体组织性能。添加涂层后,经过扩散处理,贫Cr层消失。     

线性摩擦焊接头形成过程及机理

分析了异质钛合金线性摩擦焊接头焊合线近域组织结构,结合飞边形貌及组织特点,探讨了线性摩擦焊接头的形成机理。结果表明,在线性摩擦焊接过程中摩擦界面温度超过钛合金基体材料相变点,焊后摩擦界面两侧均有高温塑性层残留并发生再结晶,焊缝区为完全再结晶组织,TC11侧焊缝区为细小针状组织,TC17侧焊缝区为亚稳态β组织。异质钛合金线性摩擦接头形成机理研究表明,在线性摩擦焊接过程中以及焊后摩擦界面始终存在,界面两侧的高温黏塑性金属没有发生机械混合,界面两侧原子发生了扩散迁移现象,在接头结合界面处形成扩散过渡区。摩擦焊通过扩散与再结晶的共同作用形成焊接接头。     

5A02铝合金TG‒TLP焊接接头的组织及性能

目的 研究5A02铝合金温度梯度瞬间液相扩散焊(TG?TLP)焊接接头的组织及性能。方法 采用TG?TLP对5A02铝合金导管进行焊接,研究温度梯度对接头的组织和力学性能的影响,为探究5A02铝合金导管的TG?TLP连接机理提供理论依据。结果 水冷铜块离焊缝的距离d=15 mm,5A02铝合金TG?TLP接头强度最高,达到90.7 MPa。随水冷铜块离焊缝的距离d的减少,接头处熔合线组织形貌由平直状到正弦状最后呈树枝状。当水冷铜块离焊缝的距离d大于15 mm时,熔合线组织形貌由平直状到正弦状,连接界面接触面积增大,接头强度提高;当水冷铜块离焊缝的距离d小于15 mm时,熔合线组织形貌由正弦状最后到树枝状,有大量的界面空隙产生,接头强度降低。结论 焊接接头强度随水冷铜块离焊缝距离的减少呈先增加后减少的变化趋势。     

SiC颗粒增强铝基复合材料的纯铜中间层液相扩散焊

采用Cu箔中间层在Ar气氛保护、550℃条件下过渡液相扩散焊(TLP)焊接SiC颗粒(SiC_P)增强Al基复合材料SiC_P/ZL101和SiC_P/Al (SiC_P 10vol%),对母材与焊接接头的微观组织、剪切强度、焊接接头剪切断面与断裂路径等进行分析。结果表明:在铸Al(ZL101)与纯Al(Al)基体中,分别通过共晶温度较低的Al-Si-Cu(524℃)三元共晶反应与Al-Cu(548℃)二元共晶反应实现中间层金属/基体金属(M/M)界面润湿。其中铸Al基体焊接接头中虽有颗粒偏聚,但由于Al-Si-Cu三元共晶反应的Cu含量(26.7wt%)低于Al-Cu二元共晶反应的Cu含量(33wt%),SiC_P/ZL101焊接接头焊缝中CuAl₂相少于SiC_P/Al焊接接头焊缝中的CuAl₂相,且未出现CuAl₂相的聚集,故其强度较高。Cu中间层形成的金属间化合物CuAl₂相是影响焊接接头力学性能的重要因素,两种复合材料焊接接头的剪切强度分别为85.4 MPa和73 MPa。      

电场对异种金属摩擦焊接头组织与性能的影响

研究了外加电场对T2紫铜和1Cr18Ni9Ti不锈钢摩擦焊接头焊合区的显微组织、主要合金元素的扩散区宽度以及接头力学性能的影响．结果表明，外加电场加快了焊合区金属的动态再结品进程，不同形式的电场对焊合区铜侧的组织形态与分布有不同的影响．在负电场(试件接电源负极)作用下，焊合区金厦发生的动态再结晶程度最大，品粒尺寸较大且分布均匀；交流电场使品粒尺寸略有减小．交流电场和负电场通过对金厦内部电子密度的影响，促进了焊接过程中焊缝区Cu、Pe和Cr的扩散，并提高了焊接接头扭转强度。     

紫铜-碳钢磁脉冲焊接接头界面形貌研究

为探索紫铜-碳钢磁脉冲焊接(MPW)接头界面形貌等微观特征,本文进行了T2紫铜管和50#钢管的磁脉冲焊接试验,在电压11 k V、径向间隙2.2 mm、重叠面积比3/4的条件下,获得了T2铜管-50#钢管冶金连接接头.通过光学金相、SEM/EDS、显微硬度和纳米压痕试验,重点研究了接头界面形貌、基体元素扩散和硬度分布.结果表明:接头由未焊合区、波状界面结合区、平直界面结合区等特征区域构成,连接区长度达到5 mm;波状结合区界面波长约为60μm,波峰幅值高约20μm;平直界面结合区基体元素扩散区(过渡区)宽度约2μm,而在波状界面结合区,扩散区宽度可达6μm;接头铜侧硬度相对初始值提高50%,最高硬度值出现在靠近界面的50号钢侧,而界面硬度介于两种母材之间.     

Ti3Al基合金与Ti-6Al-4V合金TLP连接接头的组织转变

采用TiZrNiCu合金作为中间层材料研究了Ti3Al基合金与Ti-6Al-4V合金的瞬间液相(TLP)扩散连接接头成分、组织转变及显微硬度.研究结果表明,连接温度和连接时间对接头成分和组织有较大的影响.随着连接温度的提高和连接时间的延长,接头中元素分布趋于均匀,连接区宽度增大.连接温度为850℃和900℃时,液相的残留使得接头中存在Ti-Cu金属间化合物.当连接温度为950℃,连接时间为30min时,等温凝固的完成使Ti-Cu金属间化合物从接头中消失.随着连接温度的提高和连接时间的延长,接头连接区硬度降低.当连接温度为950℃,连接时间为30min时,接头硬度分布较均匀.     

6061铝合金无倾角搅拌摩擦焊工艺及性能

目的 为了适应空间曲面构件的搅拌摩擦焊,开展6061铝合金无倾角搅拌摩擦焊工艺及性能的研究。方法 采用无倾角搅拌摩擦焊用的搅拌头,对5 mm厚6061-T6铝合金板材进行试验,研究焊缝成形及接头力学性能,并分析接头组织特征。结果 零倾角搅拌摩擦焊接头从组织上可区分为5个不同区域：焊核区(WNZ)、热力影响区(TMAZ)、热影响区(HAZ)、轴肩影响区(SAZ)和母材(BM);随着搅拌头转速增加,焊缝宽度和焊核尺寸均先变大后变小;随焊接速度增加,焊缝宽度和焊核尺寸均逐渐变小;当焊接速度固定时,随搅拌头转速增加,接头拉伸强度先增加后减小;当搅拌头转速固定时,随焊接速度增加,接头拉伸强度逐渐增大。结论 采用无倾角搅拌摩擦焊接方法,能够实现对5 mm厚6061-T6铝合金板材的有效焊接。     

镍基钎料钎焊GH586高温合金

采用非晶箔状BNi82CrSiB和BNi81CrB钎料以不同的保温时间进行钎焊实验,对钎焊接头进行了力学性能测试。利用扫描电镜和能谱分析对钎焊接头微观组织和断口进行观察和分析。结果表明,在钎焊温度下延长钎焊时间(60min)能够促进钎缝与扩散层的元素均匀分布,提高钎焊接头的室温和高温(930℃)拉伸性能。通过调整钎料合金成分,提高了钎焊接头的拉伸性能,高温拉伸性能提高22.5%。接头断裂发生在近缝区基体一侧,断裂形式主要为沿晶断裂。同时讨论了Si,B等元素对钎焊接头的组织和性能的影响。     

焊前及焊后热处理对TC11钛合金线性摩擦焊接头组织性能的影响

目的 研究焊前及焊后热处理（950 ℃+1 h+AC/540 ℃+6 h+AC）对TC11钛合金线性摩擦焊接头组织演变和力学性能的影响。方法 采用光镜、扫描电镜、显微硬度及拉伸试验对不同热处理条件下的接头进行了组织分析和力学性能测试。结果 金相结果表明，焊前热处理对焊接过程中接头的组织演变影响较小。在焊态和焊前热处理接头的焊接中心区域（WCZ）观察到类似的马氏体组织，但明显的热影响区域只能在焊前热处理接头中找到。焊后热处理后，WCZ中的马氏体组织转变为网篮组织，热力影响区（TMAZ）的初生α和转变β晶粒均有一定程度的长大。力学性能结果表明，焊前热处理可以提高整个接头的显微硬度，但硬度分布趋势与焊态接头的分布趋势相似。结论 焊后热处理可以降低WCZ和TMAZ的显微硬度，但母材的显微硬度有所提高。焊前和焊后热处理都可以提高接头抗拉强度，但会降低接头伸长率，特别是在焊前热处理条件下。     

Microstructure and mechanical properties in the TLP joint of FeCoNiTiAl and Inconel 718 alloys using BNi2 filler

High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were investigated.Owing to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy.     

The effect of gap size on the microstructure and mechanical properties of the transient liquid phase bonded FSX-414 superalloy

Optimization of transient liquid phase (TLP) bonding variables is essential to achieve a joint free from deleterious intermetallic constituents as well as with appropriate mechanical properties. In this research, TLP bonding of FSX-414 superalloy was performed using the MBF-80 interlayer. The effects of bonding time (1–30 min) and gap size (25–100 μm) were studied on the joint microstructure and its mechanical properties. Continuous centerline eutectic phases, characterized as nickel-rich and chromium-rich borides, were observed at the joints with incomplete isothermal solidification. The globular and acicular phases were seen at diffusion affected zone (DAZ). These phases could be nickel–chromium and cobalt–chromium borides. The time of complete isothermal solidification increased with increasing the gap size. This increase was consistent with the models based on the diffusion induced solid/liquid interface motion. A deviation of these models was observed for 75 and 100 μm gap size specimens. At complete isothermal solidification condition, the shear strength and the hardness of isothermal solidification zone decreased with increasing the gap size. Scanning electron microscopy (SEM) micrographs of shear fracture surfaces of the specimens with incomplete isothermal solidification showed secondary cracks through the brittle centerline eutectic constituents.     

Counteracting particulate segregation during transient liquid-phase bonding of MMC-MMC and Al2O3-MMC joints

The microstructure and mechanical properties of MMC-MMC and Al2O3-MMC joints (MMC is metal matrix composite) produced at a bonding temperature of 853 K using copper foils ranging in thickness from 10 to 30 μm were examined. The particle segregation tendency during transient liquid-phase (TLP) bonding of aluminium-based MMC material markedly increases when the aluminium-based composite material contains large number of small radius (less than 10 μm) reinforcing particles. Also, the particle segregation tendency is much greater in dissimilar Al2O3-MMC joining since the rate of solid-liquid interface movement is much slower and the time required for completing the isothermal solidification during TLP bonding is much longer. The particle segregation tendency during MMC-MMC and Al2O3-MMC bonding can be counteracted using a combination of a short (1 min) holding time at the bonding temperature (853 K) and subsequent post-weld heat treatment at 773 K for 4 h. This TLP-bonding-heat-treatment cycle removes the retained eutectic phase present at the joint centreline. This revised version was published online in November 2006 with corrections to the Cover Date.     

Transient liquid-phase bonding of ferritic oxide dispersion strengthened superalloy MA957 using a conventional nickel braze and a novel iron-base foil

It has been shown that an iron foil based on the Fe-B-Si system is a suitable material for use as a high-temperature interlayer for transient liquid-phase (TLP) bonding of ferritic oxide dispersion strengthened alloys. TLP bonding produced ferritic joints, free from intermetallic precipitates and identical in composition to that of the parent metal. In contrast, however, TLP bonding using the nickel-base foil, Bni1a, resulted in an austenitic bond region stabilized by the high nickel concentration. Furthermore, the retention of the melting point depressants, particularly silicon, at the centre of the joints resulted in the bond solidifying with the formation of silicide-boride precipitates both at the bond centre and at the braze/parent metal interface. High-temperature heat treatments failed to remove the -Fe phase and the precipitates, and their presence detrimentally affected the mechanical properties of the joint. The formation of intermetallic precipitates at the braze centre has been attributed to the initial high concentration of chromium present in the Bni1a brazing foil. Preliminary mechanical tests showed that bond strengths of joints made using the iron-base foil were superior to those obtained using the commercial nickel braze. When the iron-base foil was used, bond strengths both at room temperature and at the service temperature (700 °C) were near parent metal strengths. However, at room temperature, failure was observed to occur away from the bond interface, whilst at elevated temperatures, joints failed along the bond interface; this was attributed to the effects of melt-back phenomenon characteristic in TLP bonding.     

金属板材轧制-扩散复合机理研究进展

金属板材轧制-扩散复合集合了轧制和扩散连接的特点,对有塑性变形条件下中间层瞬间液相扩散连接过程进行研究,是研究轧制-扩散复合界面结合机理的关键.本文介绍了国内外对瞬间液相扩散连接机理实验、数学模型和数值模拟研究的进展和现状,讨论了存在的一些问题,并提出了解决方法.     

Mg/Zn/Al瞬间液相过冷连接界面的组织与性能研究

采用瞬间液相过冷连接方法对AZ31镁合金/锌中间层/5083铝合金进行连接,利用SEM、XRD、拉伸实验机和微观硬度计对结合界面的微观组织、力学性能进行了表征。结果表明,以锌作中间层,采用瞬间液相过冷连接可以实现AZ31镁合金与5083铝合金的有效连接,接头的最高抗拉强度可以达到38.5MPa,随着低温扩散保温时间的延长,扩散层厚度随之增加,接头的抗拉强度也随之升高;接头的拉伸断口属于脆性断裂,结合界面形成了MgZn2和少量的Mg17Al12金属间化合物;结合界面的微观硬度最高达170。     

Transient liquid phase bonding of magnesium alloy (Mg – 3Al – 1Zn) using copper interlayer

Abstract

The mechanism, microstructure and mechanical properties of transient liquid phase (TLP) bonded magnesium alloy (Mg – 3Al – 1Zn) joints using copper interlayers in an argon atmosphere have been investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid state diffusion, dissolution of the interlayer and base metal, isothermal solidification and homogenisation. The composition profiles and microstructures of the joint depend on the bonding time at a temperature of 530°C. With an increase in bonding time from 10 to 60 min, the concentration of copper and the amount of CuMg₂ compound in the joint decrease. For longer bonding times, the most pronounced features of the joint are composition homogenisation, grain coarsening and elimination of the bond line within the joint centre. The presence of brittle CuMg₂ and grain coarsening of the joint are the main reasons for impairing the joint shear strength. A joint shear strength of 70.2 MPa, which is 85.2% of the base metal strength (82.4 MPa), can be achieved by bonding at 530°C for 30 min.     

Al-Cu双金属复合结构的扩散连接试验研究

应用扩散连方法进行了Al-Cu双金属复合结构的试验研究，比较了不同的焊接工艺，材料组合以及母材状态情况Al合金与Cu的连接性，观察了接头区域的微观组织结构，研究表明，固相扩散连接是一种适用于异种材料连接的有效方法，通过在连接区域形成Al-Cu金属间化合物，达到Al和Cu的有效连接，材料组合，母材原始状态以及连接工艺参数对Al合金与Cu的扩散连接存在着明显的影响。表面镀Ni工艺不但能够有效阻止Al和Cu之间形成脆性相，而且Al和Ni之间形成了良好的扩散连接，改善了接头性能。     

Application of Ni and Cu nanoparticles in transient liquid phase (TLP) bonding of Ti-6Al-4V and Mg-AZ31 alloys

The transient liquid phase (TLP) bonding of Ti-6Al-4V alloy to a Mg-AZ31 alloy was performed using an electrodeposited Ni coating containing a dispersion of Ni and Cu nanoparticles. Bond formation was attributed to two mechanisms; first, solid-state diffusion of Ni and Mg, followed by liquid eutectic formation at the Mg-AZ31 interface. Second, the solid-state diffusion of Ni and Ti at the Ti-6Al-4V interface resulted in a metallurgical joint. The joint interface was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction analysis. Microhardness and shear strength tests were used to investigate the mechanical properties of the bonds. The use of Cu nanoparticles as a dispersion produced the maximum joint shear strength of 69 MPa. This shear strength value corresponded to a 15 % enhancement in joint strength compared to TLP bonds made without the use of nanoparticles dispersion.     

Effect of bonding variables on TLP bonding of oxide dispersion strengthened superalloy

Transient liquid phase (TLP) bonding has evolved as a successful alternative joining technique for high service temperature components (e.g., vanes and blades for aircraft gas turbine engines) made from superalloys when neither fusion welding nor solid-state bonding techniques are successful. However, study shows that the optimization of bonding variables is critical to achieve a metallurgically sound joint free from deleterious intermetallic constituents in the joint region. In this study, the influence of bonding pressure and interlayer thickness on microstructural developments at the joint region of TLP bonded oxide dispersion strengthened (ODS) superalloy MA758 was examined. A commercial interlayer based on the Ni–Cr–B (MBF-80) system was used and results showed that bonding pressure and interlayer thickness affected the final width of the joints. A theoretical study revealed that the TLP bonding time can also be reduced when there is an increase in bonding pressure.