间隙大小对瞬时液相连接IN-738LC高温合金显微组织的影响（英文）

以AMS 4777粉末为填料,研究瞬时液相连接IN-738LC高温合金的显微组织演变,获得完全等温凝固时间。研究间隙大小和连接时间对接头组织的影响。当间隙大小为40μm时,完全等温凝固时间为45 min。在不完全等温凝固的情况下,连接区的残余液相在非平衡条件下冷却,形成γ-γ共晶相。间隙大小与时间存在非线性关系。随着间隙增大,共晶相变宽。在扩散影响区,发现大量合金元素,其浓度达到峰值,这是由于形成了硼化物和硅化物等金属间化合物。随着间隙增加,所需连接时间增加,合金元素有更多的时间进行扩散和分布至更大区域。因此,合金元素浓度随间隙增加缓慢降低。已有双相模型不能准确预测IN-738LC-AMS 4777-IN738LC瞬时液相连接系统的完全等温凝固时间。     

单晶高温合金的过渡液相扩散焊

为了探明单晶过渡液相(TLP)扩散焊接头组织与性能的关系,采用扫描电镜(SEM)研究接头微观组织,并进行力学性能测试. 结果表明,接头由连接区和基体区所组成. 当等温凝固过程未完成时,连接区由等温凝固区和快速凝固区组成,而等温凝固区主要由γ和γ'相组成,快速凝固区主要是由共晶组织组成. 当等温凝固完成而固态均匀化过程不充分时,连接区由等温凝固区和分布在接头中心的硼化物相组成. 采用低温等温凝固,高温固态均匀化的焊接工艺可以获得高性能的接头.     

DZ38G高温合金扩散钎焊微观结构分析

在真空环境下采用Ni-Si-B中间层,扩散钎焊DZ38G高温合金,扩散连接温度为1050℃,扩散连接时间为30～70min,焊后均质化保温温度为1050℃,保温时间为300 min.研究了接头的微观结构.研究表明:等温凝固完成前,接头主要有四种不同的相构成:初始共晶的γ固溶体、Ni基硼化物、共晶的γ固溶体和母材金属;在1050℃下,扩散钎焊时间70 min以上,可完成等温凝固.     

BNi68CrWB钎焊K24/GH648异种高温合金的界面形成机理

采用BNi68CrWB钎料粉末对K24和GH648异种高温合金进行钎焊连接,分析了接头典型界面组织,提出了钎焊过程反应机理.结果表明,接头由共晶区、等温凝固区和扩散区组成.共晶区由WB,CrB和镍基固溶体组成,等温凝固区为镍基固溶体,GH648侧扩散区由WB,W_xB_y,Cr_xB_y,以及沿晶界析出的镍基固溶体和少量的Cr₂Ni₃相组成,K24侧扩散区与母材差异不明显.钎焊过程由元素富集、母材溶解、等温凝固和共晶凝固四个阶段组成.其中等温凝固阶段是钎焊过程中最关键的阶段,等温凝固不完全时,钎缝中央存在共晶组织,影响接头性能.钎焊温度1 150℃,保温120 min时,等温凝固完全,接头组织均匀,力学性能最优,室温拉剪强度可达323 MPa.     

焊接工艺对瞬时液相焊接头组织及性能的影响

以Ni-Cr-B非晶薄片作为连接中间层,对Mar-M247镍基高温合金进行瞬时液相焊,采用光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)和硬度测试仪研究了焊接温度及时间对接头组织和性能的影响。结果表明:中间层和基体发生扩散反应,在保温时间不充分时,连接层内形成了非等温凝固区,其组成为镍基固溶相,富Ni硼化物和富Cr硼化物。在温度一定时,随着保温时间的增加,非等温凝固区宽度逐渐减小,最后形成完全等温凝固区,试样接头的断裂方式也由脆性断裂转变为韧性断裂。当保温时间一定时,升高焊接温度至1150℃,接头组织中非等温凝固区占比最小,力学性能最佳,极限拉伸强度为845 MPa,伸长率为11.5%。     

焊后热处理对CB2耐热钢焊接头组织及力学性能的影响

采用BNi-2非晶薄片作为连接中间层,分别在温度为1060℃,1100℃和1140℃,保温时间为1800 s的条件下,对CB2耐热钢进行瞬时液相焊接,并对接头进行焊后热处理。采用扫描电镜(SEM)和能谱仪(EDS)对接头显微组织和元素分布进行分析,并对接头的力学性能进行测试。结果表明,在焊接过程中,中间层和基体发生明显相互扩散。在1060℃的焊接温度下,接头中心处形成了非等温凝固区,其组成主要为富Cr硼化物。随着连接温度的增加,非等温凝固区消失,形成完全等温凝固区。在接头的扩散影响区,有Cr硼化合物的出现,在温度为1100℃时,其数量达到最大值,而后随温度增加而减少。接头的抗拉强度在1140℃达到最大值为920 MPa,而伸长率低于7%,拉伸断裂发生在接头。在经过焊后热处理后,接头的等温凝固区域宽度增加,而扩散影响区中的Cr硼化物减少,拉伸断裂以韧性断裂方式发生在母材,强度降低为723 MPa,但断后伸长率明显提升至19%,达到原始母材的性能,因此焊后热处理可以优化接头的力学性能。     

镁合金与不锈钢的瞬间液相扩散连接

以Cu箔为中间夹层对AZ31B镁合金与304不锈钢进行瞬间液相扩散连接,研究了焊接接头的微观结构和连接强度。结果表明,在510℃/30 min、530℃/10 min下进行扩散连接时,接头界面区没有出现共晶液相,界面结合较弱;520℃/30 min、530℃/20 min时,接头界面区形成Mg-Cu共晶液相,焊缝宽度显著增加,界面结合强度提高;530℃/30min时,镁基体一侧形成350μm的层状扩散区,接头显微组织依次是Mg-Cu共晶组织层、富Mg固溶体层、弥散分布于镁合金基体的Mg17(Cu,Al)12相和分布于镁合金晶界的Mg-Cu-Al三元化合物所组成的镁合金基体渗透区,其剪切强度达到最大(52 MPa);540℃/30 min、530℃/40 min时,界面扩散区的共晶液相发生等温凝固,镁合金基体晶界处Mg-Cu-Al三元金属间化合物呈连续网状分布,接头的剪切强度降低。AZ31B基体发生了再结晶及晶粒长大。     

FGH97高温合金TLP焊接接头组织分析

采用BNi82CrSiB中间层材料对FGH97高温合金进行了过渡液相(TLP)焊,研究了焊接温度为1150℃不同保温时间条件下的接头组织.结果表明,随保温时间的延长,焊缝宽度逐渐增大,焊缝中等温凝固区γ固溶体的数量逐渐增多,而焊缝中央非等温凝固区树枝状γ/Ni2B共晶、γ/γ'共晶、Ni3Si、M23B6和Cr2B等物相逐渐减少并消失,最后形成致密的γ固溶体焊缝组织.同时,随保温时间的延长,焊缝两侧扩散区的宽度逐渐增大,且有针状、颗粒状和蠕虫状的M3B2型硼化物析出,且越远离焊缝,析出相的数量越少.     

以BNi-2非晶为中间层的CB2耐热钢瞬时液相扩散连接的接头组织和性能研究（英文）

主要研究采用BNi-2非晶态中间层的CB2耐热钢瞬时液相(TLP)扩散连接接头组织和性能,及焊后热处理(PBHT)对接头组织和性能的影响。富Cr硼化物和Cr-Mo硼化物出现在接头的过渡区和扩散影响区,其尺寸和数量在等温凝固完成时达到最大值。随着连接温度和时间的增加,富Cr的硼化物和Cr-Mo硼化物逐渐减少,而BN相逐渐增多。经过焊后热处理后,接头的富Cr硼化物几乎全部消失,而BN相的尺寸和数量增加。在热处理之前,焊接温度为1150℃,保温时间1800 s的接头有最大抗拉伸强度,为934 MPa,延伸率为5.3%。通过焊后热处理,断裂发生在母材,而其延伸率显著提高到20%,而抗拉伸强度降低到720 MPa,其性能与原始的母材性能相近。     

以BNi2非晶为中间层的CB2耐热钢瞬时液相扩散连接的接头组织和性能研究

本文主要研究采用BNi2非晶态中间层的CB2耐热钢瞬时液相扩散连接接头组织和性能,及焊后热处理对接头组织和性能的影响。富Cr硼化物(CrB, CrB2, Cr2B3, Cr3B4 and Cr5B3)和Cr-Mo硼化物出现在接头的过渡区和扩散影响区,其尺寸和数量在等温凝固完成时达到最大值。随着连接温度和时间的增加,富Cr的硼化物和Cr-Mo硼化物逐渐减少,而BN相逐渐增加。经过焊后热处理后,接头的富Cr硼化物几乎全部消失,而BN相的尺寸和数量增加。在热处理之前,焊接温度为1150°C ,保温时间1800s的接头有最大的拉伸强度为934 MPa,延伸率为5.3%。通过焊后热处理,断裂发生在母材,延伸率提升到20%,而拉伸强度降低到720 MPa。     

New insights into microstructural changes during transient liquid phase bonding of GTD-111 superalloy

The effects of joining temperature (T_J) and time (t_J) on microstructure of the transient liquid phase (TLP) bonding of GTD-111 superalloy were investigated. The bonding process was applied using BNi-3 filler at temperatures of 1080, 1120, and 1160 °C for isothermal solidification time of 195, 135, and 90 min, respectively. Homogenization heat treatment was also applied to all of the joints. The results show that intermetallic and eutectic compounds such as Ni-rich borides, Ni−B−Si ternary compound and eutectic-γ continuously are formed in the joint region during cooling. By increasing t_J, intermetallic phases are firstly reduced and eventually eliminated and isothermal solidification is completed as well. With the increase of the holding time at all of the three bonding temperatures, the thickness of the athermally solidified zone (ASZ) and the volume fraction of precipitates in the bonding area decrease and the width of the diffusion affected zone (DAZ) increases. Similar results are also obtained by increasing T_J from 1080 to 1160 °C at t_J=90 min. Furthermore, increasing the T_J from 1080 to 1160 °C leads to the faster elimination of intermetallic phases from the ASZ. However, these phases are again observed in the joint region at 1180 °C. It is observed that by increasing the bonding temperature, the bonding width and the rate of dissolution of the base metal increase. Based on these results, increasing the homogenization time from 180 to 300 min leads to the elimination of boride precipitates in the DAZ and a high uniformity of the concentration of alloying elements in the joint region and the base metal.     

Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal

The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) filler metal. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone, borides/silicide formation during eutectic-type solidification in an athermal solidification zone, on-cooling precipitation of fine nickel silicides in the joint centerline, in situ precipitation of Mo–Cr-rich borides in the diffusion affected zone and grain growth in the heat affected zone. The implication of the phase transformations on the joint properties is discussed. It is shown that Hastelloy X exhibited very fast isothermal solidification which can be attributed to its high Mo and Cr content that promotes in situ boride precipitation during brazing.     

Microstructural and mechanical properties assessment of transient liquid phase bonding of CoCuFeMnNi high entropy alloy

The transient liquid phase (TLP) bonding of CoCuFeMnNi high entropy alloy (HEA) was studied. The TLP bonding was performed using AWS BNi-2 interlayer at 1050 °C with the TLP bonding time of 20, 60, 180 and 240 min. The effect of bonding time on the joint microstructure was characterized by SEM and EDS. Microstructural results confirmed that complete isothermal solidification occurred approximately at 240 min of bonding time. For samples bonded at 20, 60 and 180 min, athermal solidification zone was formed in the bonding area which included Cr-rich boride and Mn₃Si intermetallic compound. For all samples, the γ solid solution was formed in the isothermal solidification zone of the bonding zone. To evaluate the effect of TLP bonding time on mechanical properties of joints, the shear strength and micro-hardness of joints were measured. The results indicated a decrement of micro-hardness in the bonding zone and an increment of micro-hardness in the adjacent zone of joints. The minimum and maximum values of shear strength were 100 and 180 MPa for joints with the bonding time of 20 and 240 min, respectively.     

Aging response of transient liquid phase bonded wrought IN718 superalloy: influence of post-bond heat treatment

Aging response of transient liquid phase Nb bearing wrought IN718 nickel base superalloy is studied. The aging behaviour of the joint is influenced by low Nb+Al+Ti content of isothermal solidification zone (ISZ) and formation of Nb–Cr–Mo based boride precipitates in diffusion affected zone (DAZ). It was shown that applying a post-bond heat treatment which was able to eliminate the diffusion induced boride precipitates in DAZ and increase the Nb+Al+Ti content of the ISZ improved the aging response and shear strength of the joint.     

时效温度对非平衡凝固K424合金析出相及硬度的影响

采用铜模喷铸与等温时效相结合的方法,研究了快冷K424高温合金的非平衡凝固组织及其沉淀相析出行为。结果表明,铜模喷铸合金组织发生了显著细化,二次枝晶间距相比铸态大幅降低,溶质偏析的减弱有利于抑制粗大碳化物及共晶组织形成。随铜模内径下降,枝晶形貌由无方向性等轴晶逐渐转变为择优生长的定向枝晶。经800~1000℃等温时效30min后,快冷合金的过饱和固溶体组织中开始析出γ′相。随时效温度提高,沉淀相尺寸及体积分数同时增加。900℃×30min时效后可获得大量细小均匀的球形γ′相,快冷合金的显微硬度(HV)高达478,相比原始非平衡态合金提高了13%。     

Abnormal austenite–ferrite transformation behaviour in substitutional Fe-based alloys

The γ→α phase transformation behaviours of Fe-Co and Fe-Mn alloys were systematically investigated by dilatometry and Differential Thermal Analysis (DTA). Two kinds of transformation kinetics, called normal and abnormal, were recognized for the first time and classified according to the variation of the ferrite formation rate. These transformation characteristics were observed for both isothermally and isochronally conducted annealing experiments. A transition, from abnormal to normal transformation kinetics, occurs for Fe-1.79at.%Co when successive heat treatment cycles are executed, which contrasts with Fe-2.26at.%Mn for which only normal transformation kinetics occurs after each of all successive heat treatment cycles. A possible mechanism for the appearance of abnormal transformation kinetics is given, which is based on the austenite grain size. Light microscopical analysis indicates a repeated nucleation of ferrite in front of the migrating γ/α interface.     

超窄间隙焊接Q235/1Cr18Ni9Ti异种钢接头组织及力学性能

超窄间隙焊接厚壁异种钢具有高效、低成本、接头力学性能优良的独特优势.文中研究了Q235/1Cr18Ni9Ti异种钢超窄间隙焊接接头的微观组织及力学性能.结果表明,打底焊的熔池以FA模式凝固,凝固组织为细小的奥氏体等轴晶及少量枝晶状铁素体.填充焊和盖面焊在靠近熔合过渡区的熔池区域以AF模式凝固,凝固组织为奥氏体胞状晶及胞状晶间铁素体,在远离熔合过渡区的熔池区域则以FA模式凝固,凝固组织为奥氏体柱状树枝晶及少量骨架状铁素体.异种钢超窄间隙焊接接头的抗拉强度和弯曲性能优良,Q235一侧HAZ未出现软化,熔合过渡区及其一侧HAZ的韧性优于焊缝区.     

Microstructure－properties relationship of transient liquid phase diffusion bonded a third generation single crystal superalloy joint

Microstructure of transient liquid phase( TLP) diffusion bonded a third generation single crystal superalloy joint was investigated using scanning electron microscopy( SEM),and mechanical properties test of joint was carried out,for obtaining relationship between microstructure and mechanical properties of joint. The results showed that the joint contained bonding zone and base metal. The diffusion zone was obviously observed. When it was not finished for isothermal solidification process,the bonding zone would contain isothermal solidification zone and rapid solidification zone. Metallographic examination revealed that isothermal solidification zone was consisted of γ and γ' phase. Rapid solidification zone was consisted of two different structures,which were ternary eutectic of borides,γ and γ' phase developing at the edge of joint,binary eutectic of γ and γ' phase appearing in the portion of joint. When it was not enough for homogenization process under the condition of finishing isothermal solidification process,the bonding zone would contain isothermal solidification zone and borides at the interface. Under the conditions of relatively high welding temperature and long welding time,average tensile strength of joint was equivalent to that of parent material.     

IC10单晶过渡液相扩散焊接头微观组织与力学性能

采用扫描电镜（SEM）和能谱分析仪（EDS）研究IC10单晶高温合金过渡液相（TLP）扩散焊接头微观组织演变．结果表明,接头由连接区和基体区所组成,连接区由等温凝同区和快速凝固区组成．快速凝固区可以通过延长保温时间的方法予以消除．随着保温时间从2h增加到8h,基体内的γ＇相尺寸达到了0．9μm．通过限制TLP扩散焊接头内晶界的形成,以及焊后固溶处理的方法可以有效提高接头的力学性能．在温度1000℃下,接头平均抗拉强度为507MPa．在温度1000℃、应力144MPa下接头持久寿命可达到120h以上．