β型γ-Ti Al合金中硼化物的取向及其对α相的影响

本实验在β单相区分别对Ti-40Al-8Nb-0. 5B及Ti-40Al-8Nb-1B合金进行了热变形,研究了两种合金中硼化物的取向行为及其对α相的影响。结果表明:热变形及硼含量显著影响硼化物的分布状态。未变形时,两种合金中的硼化物均为随机分布;变形后,Ti-40Al-8Nb-0. 5B合金中硼化物呈现出强烈的[100]丝织构,而Ti-40Al-8Nb-1B合金中硼化物取向随机,这是由变形过程中硼化物的刚性旋转及其相互作用所造成的。经历β→α相变后,Ti-40Al-8Nb-0. 5B合金α相呈现出1120和1010双丝织构,而Ti-40Al-8Nb-1B合金α相取向随机,这归因于硼化物、β相以及α相之间的组织遗传性。本研究可为β型γ-Ti Al合金片层取向控制提供新的思路。     

FGH95镍基合金的电解萃取及相组成与分布特征

通过对热处理态FGH95合金进行电解萃取,组织形貌观察及XRD分析,研究了FGH95合金的相组成及γ′相的粒度分布.结果表明,经1140℃固溶和时效处理后,合金的组织结构由γ′,γ相,(Nb,Ti)C、( Nb,W)B2,Nb13B2和Cr23C6等碳、硼化物组成,其中合金中γ′,γ基体相的质量分数分别为47.8％和51.2％,其碳、硼化物的质量分数约为1％.合金中晶内为细小γ′相弥散分布,而粗大γ′相沿较宽的颗粒边界区域不连续析出;其中,在36～60nm之间的γ′相粒子质量分数为30.6％,在60～96nm之间的γ′相粒子质量分数为29.1％,γ′相的结构组成式为:(Ni0.896C00.055Cr0.017Fe0.031)3 (Ti0.224Nb0.134Al0.473Mo0.038W0.066 Cr0.064).     

球磨时间对MA-SPS法制备FeCoCrAlNiB高熵合金微观结构、硬度和断裂韧性的影响

采用机械合金化(MA)和放电等离子烧结(SPS)相结合的方法制备FeCoCrAlNiB高熵合金。研究球磨时间(1、5、10、20、30和40 h)对合金相成分、微观结构、硬度和断裂韧性的影响。结果表明：高能球磨过程中各金属元素的合金化顺序为Al→Co→Ni→Fe→Cr;混合粉末球磨20 h后基本形成了单一的BCC固溶体相,其颗粒尺寸约为20μm。对不同球磨时间的混合粉末进行SPS烧结,获得的FeCoCrAlNiB高熵合金主要由无序BCC+B2(Al-Ni)固溶体相和硼化物相(Fe₂B等)组成。随着球磨时间的延长,合金中硼化物相含量先减少后增加并主要以网状形式分布,BCC相含量则与之相反;合金硬度随球磨时间的延长逐渐提高,主要是因为合金元素间固溶程度越来越高,硼化物相逐渐增多;但硼化物形成的网状结构会破坏基体的连续性,导致合金断裂韧性逐渐降低。当球磨时间为20 h时,获得的FeCoCrAlNiB高熵合金的维氏硬度(HV)为(10.9±0.2) GPa,断裂韧性(K_IC)为(4.4±0.2) MPa·m^1/2,表现出最优的综...     

IC-6合金TLP连接接头组织对高温拉伸性能的影响

研究了采用镍基含硼中间层合金在１２２０℃保温不同时间连接ＩＣ－６合金时,接头９００℃拉伸性能的变化。结果表明接头拉伸强度并未随扩散时间延长而不断提高。从断口 分析可知,焊缝组织中的晶界强度和近缝区硼化物的形态、分布及数量决定了接头的拉伸强度和塑性。焊缝中的晶界强度高,裂纹沿晶界扩展至不利取向,转而沿近缝区硼化物扩展,断口上沿晶断裂所占区域少,对应接头强度较高,且具有一定的塑性。若晶界强度低,断口上主要表现为沿晶断裂,接头强度较低,且塑性差,在外应力作用下,硼化物发生脆性解理或由于与基体结合力低而脱开,其周围的包膜可以缓解硼化物上的应力集中使裂纹扩展需要的应变能增加。     

K640合金钎焊接头组织及工艺控制

采用不同的工艺参数对铸造钴基高温合金K640进行了钎焊实验,通过扫描电镜、能谱分析仪和X射线衍射仪对钎焊接头进行了微观组织观察、典型物相成分测试及物相分析.结果表明:不同钎焊工艺参数下的钎缝均由钴基固溶体、碳化物M23C6、硼化物M3B2 钴基固溶体共晶,以及块状及颗粒状碳化物MC组成.当钎焊温度较低或保温时间较短时,钎缝中央生成大量的M3B2;随着钎焊温度的升高及保温时间的延长,钎缝中M3B2、MC减少,M23C6增多、长大.     

等离子熔覆含亚微米碳化铌铁基耐磨合金组织与性能的研究

采用等离子熔覆(PTA)在Q235钢上制备含亚微米碳化铌Fe-Cr-B-C-Nb熔覆层,通过改变合金成分,分别设计含超细碳化铌、含共晶硼化物、含超细碳化铌+共晶硼化物、含超细碳化铌+初生Fe2B硬质相的熔覆层,研究不同尺寸硬质相对Fe-Cr-B-C-Nb熔覆层组织与性能的影响,并与市售常用Fe-Cr-C耐磨材料对比。结果表明:细小硬质相有助于改善合金冲击变形能力,含亚微米碳化铌和共晶硼化物的合金具有优良的综合性能,耐磨性为Fe-Cr-C耐磨材料的4倍多,且冲击变形能力优于Fe-Cr-C耐磨材料。     

电弧熔炼过程中LaFe10Si3合金的凝固组织和相形成研究

研究了电弧熔炼过程中LaFe_(10)Si_3合金的凝固行为。应用XRD和扫描电镜分析了合金组织相组成和结构。结果表明:温度梯度和成分偏析造成LaFe_(10)Si_3合金铸锭显微组织大致分成了5层,从样品四周到中部,析出1∶13相形貌依次为板条状、椭圆状、柱状、等轴晶状和羽毛状;La(Fe,Si)13合金铸锭中1∶13相析出方式应该有3种,直接析出形成等轴晶,1∶13相包裹α-Fe相形成包晶相析出,1∶13相与1∶1∶1相和1∶2∶2相共晶析出。     

BMIC-ZnCl2离子液体中电沉积铜-锌合金

在含有CuCl的BMIC-ZnCl2(物质的量比为1∶2)离子液体中,采用恒电位法于低碳钢基体上进行了Cu-Zn合金电沉积实验.研究了CuCl的浓度、沉积电位、温度对Cu-Zn合金成分、形貌及电流效率的影响,并采用带X射线能量散射谱(EDS)的扫描电子显微镜(SEM)及X射线衍射仪对所得Cu-Zn合金沉积层的成分、表面形貌及物相进行分析.结果发现当电解液中CuCl的浓度为0.2mol/L时,阴极沉积电位在-0.1V附近,温度为70℃时,可得到质量较好的Cu-Zn合金仿金镀层.     

硼和超声波对Ti42Al6Nb2.6C0.8Ta合金组织性能耦合作用机制研究

目的 为了揭示超声辅助熔铸下硼(B)和超声波的耦合细化机制及其强化机制,研究Ti42Al6Nb2.6C0.8Ta?xB合金的相组成、片层团尺寸、元素分布、析出相的种类和形貌、压缩性能及相应机制。方法 在氩气气氛保护下用真空非自耗电弧对合金进行熔炼,然后通过超声设备重熔引入超声波,超声电流恒定,超声作用时间为100 s。随后对合金组织进行扫描电镜观察和相组成分析,并测试其室温压缩性能。结果 TiAl合金中硼化物的种类和含量得到了调控,片层团尺寸从30.3 μm降低到16.6 μm,β稳定元素的偏析减少,B2相含量降低。合金压缩性能大幅度提高,压缩强度从1 701 MPa增加到2 176 MPa,压缩率从25.5 %增加到32.6 %。结论 B元素引起的成分过冷、异质形核质点的增加和超声波对初生相的破碎三者共同作用,细化了合金的组织。显微组织细化、Nb和Ta的固溶、棒状硼化物含量的增加和B2相含量的降低是压缩性能提高的主要原因。     

铸造铝镍钴合金的组织与性能研究

采用化学成分分析、合金结构形貌分析、磁特性分析等研究了LNG37等铸造铝镍钴永磁合金的组织结构形貌及化学成分,相组织转变过程及与热处理的关系,组织与获得最佳磁特性的关系。研究表明,随着合金组织中αγ相的增多,合金的磁特性(Br、Hc、(BH)max)随之下降,尤其是磁能积(BH)max下降最为显著,合金元素含量与热处理制度是合金获得理想磁特性的关键因素,热处理过程中应使合金快速通过(α+γ)两相区,控制α1+α2的良好分解和抑制γ相的出现。     

Microstructure and strength of TiC cermet/cast iron brazed with Ag – Cu – Zn filler metal

Abstract

The brazing of TiC cermet to cast iron was carried out at 1223 K for 5 – 30 min using Ag – Cu – Zn filler metal. The formation phases, interface structures and shear strengths of the joints were investigated. The experiment result and analysis identify that three new phases, namely Cu base solid solution, Ag base solid solution and (Fe, Ni) have formed during the brazing of TiC cermet to iron. The interface structure of the joints can be expressed as TiC cermet/Cu base solid solution/Ag base solid solution + a little Cu base solid solution/Cu base solid solution + (Fe, Ni)/cast iron. The highest shear strength of the joints is 292.0 MPa, obtained with a brazing time of 20 min.     

Microstructure and strength of TiAl/steel joint induction brazed with Ag-Cu-Ti filler metal

Abstract

Intermetallic TiAl was induction brazed to steel in an induction furnace with Ag-Cu-Ti filler metal at 1143 K for 0·2–2·4 ks. Microstructural analysis indicates that Ti, Al, and C atoms in base metal diffuse to the interface and react strongly with the filler metal during brazing. The interface structure of the joint can be divided into three distinct zones: the reaction layer near TiAl, composed of Cu-Al-Ti compounds and Ag based solid solutions; the central zone of the interface, consisting of Ag based solid solutions in which Ag-Cu eutectic phases are dispersed; a TiC reaction layer adjacent to the steel. The relationship between brazing parameters and tensile strength of the joints is discussed, and the optimum induction brazing parameters obtained. When brazed at 1143 K for 0.9 ks, the tensile strength of the joint is 298 MPa.     

Evaluation of transient liquid phase bonding between nickel-based superalloys

Induction brazing of Inconel 718 to Inconel X-750 using Ni-7Cr-3Fe-3.2B-4.5Si (wt.-%) foil as brazing filler metal was investigated in this paper. Brazing was conducted at the temperature range 1373–1473 K for 0–300 s in a flow argon environment. Both interfacial microstructures and mechanical properties of brazed joints were investigated to evaluate joint quality. The optical and scanning electron microscopic results indicate that good wetting existed between the brazing alloy and both Inconel 718 and Inconel X-750. Microstructures at joint interfaces of all samples show distinct multilayered structures that were mainly formed by isothermal solidification and following solid-state interdiffusion during joining. The diffusion of boron and silicon from brazing filler metal into base metal at the brazing temperature is the main controlling factor pertaining to the microstructural evolution of the joint interface. The element area distribution of Cr, Fe, Si, Ni and Ti was examined by energy dispersive X-ray analysis. It was found that silicon and chromium remain in the center of brazed region and form brittle eutectic phases; boron distribution is uniform across joint area as it readily diffuses from brazing filler metal into base metal. The influence of heating cycle on the microstructures of base material and holding time on the mechanical properties of brazed joint were also investigated.     

PTLP Joining of Al2O3-Stainless Steel 304 Using Ni-Cr Foil—The Microstructure Morphologies of Joint Interfaces

Partial-transient liquid-phase brazing of Al₂O₃-stainless steel (SS) 304 using a Ni-Cr foil as a refractory layer in brazing filler metals was investigated in a vacuum environment, and the microstructures in the joints were studied in detail. The cross-sectioned microstructures at joint interfaces show multilayered structures. Six characteristic zones can be distinguished in the joint, named as base alumina zone, titanium reaction zone, roughly homogenized filler materials zone, discontinuous precipitation zone, metallic brazing zone, and base metal zone. The main corresponding phases of these six zones are Al₂O₃(I), TiO+CuTiO₄(II), Ni(Cu)-Cr-Ti(III), Ni(Cu)-Cr+Ti+Fe-Ti(IV), SS304 (V, VI), respectively. Experimental results demonstrated that the formation of TiO and CuTiO₄can improve greatly the wettability of Al₂O₃, and, thus, the good joint was obtained at the interface of Al₂O₃and filler metal. Part of the Ti atoms can diffuse into the interface between SS304 and filler materials and form intermetallics, which precipitate as hard and brittle precipitation during the cooling stage.     

铜-铝合金CPU散热器钎焊技术研究

介绍了一种环保型钎焊膏及其在CPU散热器铝合金／铜钎焊中的应用．结合散热器的铝合金-铜结构,分析了利用钎焊膏进行钎焊的过程．结果表明,钎焊可以在气体保护炉中进行,也可利用高频电源在空气气氛中进行．钎焊时在铝散热器与铜板之间发生了明显的反应,反应的液相在深度方向上有明显的晶界优先扩展取向,当在接触点发生反应产生液相后,反应得以持续进行的驱动力是Al、Cu原子通过固／液界面向反应液相中的扩散和溶解,在母材表面以下的金属学组织为Al—Cu—X和纯Al的两相组织．LHG—S2钎焊膏钎焊铜-铝合金散热器,钎焊缝的致密性完全可以达到散热器设计的技术要求,诸如传热效率及外观等．     

Study on cold metal transfer welding–brazing of titanium to copper

3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti₂Cu, TiCu and AlCu₂Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface.     

SiC陶瓷与316L不锈钢真空活性钎焊

采用Ag-Cu-Ti活性钎料,通过真空钎焊方法进行了SiC陶瓷与316L不锈钢的连接,研究了接头的界面组织、特征点成分和物相,并探讨了钎焊温度(800~930℃)、保温时间(0~30 min)对接头界面组织和连接强度的影响。结果表明,SiC陶瓷与316L不锈钢钎焊抗剪断口均发生在SiC陶瓷与钎料连接界面处,由于活性元素Ti的作用,在陶瓷与钎料的界面处形成了连续的反应层,反应生成了Ti C和Ti₅Si₃;在316L不锈钢与钎料的界面处,生成了Fe-Ti化合物和Cu-Ti化合物。随着钎焊温度升高及保温时间延长,接头强度均呈现出一个峰值,在温度为900℃,保温20 min的工艺条件下可获得最大接头抗剪强度。     

Formation of the reaction zone between tin‐copper brazing fillers and aluminum‐silicon‐magnesium alloys: Experiments and thermodynamic analysis

A primary challenge in brazing is the controlled formation of phases resulting from interactions of elements of the liquid filler metal with those of the base material. The morphology of the brazed joint, which is decisive for the mechanical properties of the joint, is influenced by present elements and process parameters such as brazing temperature and time. Furthermore, the wetting of the base material is a crucial factor in joining of aluminum because of the low wettability of the alumina layer by molten brazing filler metals. In order to remove the alumina and prevent reoxidation of the substrate surface, the brazing process can be conducted in vacuum or inert gas atmosphere. Again, selection of process parameters is crucial for the quality of the brazed seam. In this work, we focus on the influence of the process parameters on the wetting behavior and the formation of aluminum‐copper phases theoretically by means of thermodynamic calculations using a CALPHAD database as well as by means of in‐situ observations in the large‐chamber scanning electron microscope (LC‐SEM) and by brazing experiments. Both the critical temperatures with respect to the wetting and the reaction kinetics as well as the crucial stages of the brazing process and the resulting phases were determined.     

电子束钎焊接头组织分析

采用自主开发的电子束钎焊系统,对不锈钢毛细管板结构进行钎焊,通过电子探针显微分析仪研究了不同电子束钎焊规范下BNi-2钎料与管壁基体界面合金元素的分布,分析了钎料和界面区各相的化学组成.研究表明:在加速电压60kV,束流6.5 mA,加热时间37 s,扫描幅值O.5的电子束钎焊规范下,管板接头质量满足技术规范要求;随着电子束输入功率或功率密度增大,钎料和管壁的相互扩散作用增强,导致过渡层厚度增加,毛细管壁显著减薄;母材和钎料中合金元素的相互扩散导致过渡层的形成,过渡层主要由硼化铬、硼化镍和镍的固溶体组成.     

铝合金中温自反应钎焊机理的研究

在AlF3-CsF共晶钎剂中添加ZnCl2和SnCl2两种活化物质,制备出可用于钎焊薄板铝合金的中温自反应钎剂。研究钎剂中活化物质含量和T形接头连接面积对接头界面组织与力学性能的影响。采用金相光学显微镜、扫描电子显微镜和能谱仪对钎焊接头微观组织、相成分、缺陷及断口形貌进行分析。结果表明:当钎剂中两种活化物质添加量都在4%(质量分数)左右时,钎焊接头连接最致密;钎焊时钎剂中的Zn2+和Sn2+与两侧母材中的Al原子发生置换反应生成液态金属Sn与Zn,与Al互溶度大的Zn迅速向母材扩散,而Sn由于在Al中固溶度小,与少量Zn和Al残留在界面上形成低熔点金属层;自反应钎剂易实现小连接面积接头的连接;接头拉伸断口中有大量韧窝存在,抗拉强度达到(58±5)MPa。