Brazeability evaluation of Ti-Zr-Cu-Ni-Co-Mo filler for vacuum brazing TiAl-based alloy

Ti-47Al-2Nb-2Cr-0.15B(mole fraction,%)alloy was vacuum brazed with amorphous and crystalline Ti.25Zr-12.5Cu-12.5Ni-3.0Co-2.0Mo(mass fraction,%)filler alloys,and the melting,spreading and gap filling behaviors of the amorphous and crystalline filler alloys as well as the joints brazed with them were investigated in details.Results showed that the amorphous filler alloy possessed narrower melting temperature interval,lower liquidus temperature and melting active energy compared with the crystalline filler alloy,and it also exhibited better brazeability on the surface of the Ti.47Al.2Nb.2Cr.0.15B alloy.The TiAl joints brazed with crystalline and amorphous filler alloys were composed of two interfacial reaction layers and a central brazed layer.Under the same conditions,the tensile strength of the joint brazed with the amorphous filler alloy was always higher than that with the crystalline filler alloy.The maxmium tensile strength of the joint brazed at 1273 K with the amorphous filler alloy reached 254 MPa.

Contact reactive brazing of Al alloy/Cu/stainless steel joints and dissolution behaviors of interlayer

Contact reactive brazing of 6063 Al alloy and 1Cr18Ni9Ti stainless steel was researched by using Cu as interlayer. Effect of brazing time on microstructure of the joints, as well as the dissolution behaviors of Cu interlayer was analyzed. The results show that the product of reaction zone near 1Cr18Ni9Ti is composed of Fe2Al5, FeAl3 intermetallic compound （IMC）, and Cu-Al IMC; the near by area is composed of Al-Cu eutectic structure with Al （Cu） solid solution. With increasing the brazing time, the thickness of IMC layer at the interface increases, while the width of Al-Cu eutectic structure with Al（Cu） solution decreases. Calculation shows the dissolution rate of Cu interlayer is very fast. The complete dissolution time is about 0.47 s for Cu interlayer with 10 μm in thickness used in this study.

Improving pulsed laser weldability of duplex stainless steel to 5456 aluminum alloy via friction stir process reinforcing of aluminum by BNi-2 brazing alloy

Effects of laser pulse distance and reinforcing of 5456 aluminum alloy were investigated on laser weldability of Al alloy to duplex stainless steel (DSS) plates. The aluminum alloy plate was reinforced by nickel-base BNi-2 brazing powder via friction stir processing. The DSS plates were laser welded to the Al5456/BNi-2 composite and also to the Al5456 alloy plates. The welding zones were studied by scanning electron microscopy, X-ray diffractometry, micro-hardness and shear tests. The weld interface layer became thinner from 23 to 5 μm, as the laser pulse distance was increased from 0.2 to 0.5 mm. Reinforcing of the Al alloy modified the phases at interface layer from Al-Fe intermetallic compounds (IMCs) in the DSS/Al alloy weld, to Al-Ni-Fe IMCs in the DSS/Al composite one, since more nickel was injected in the weld pool by BNi-2 reinforcements. This led to a remarkable reduction in crack tendency of the welds and decreased the hardness of the interface layer from ~950 HV to ~600 HV. Shear strengths of the DSS/Al composite welds were significantly increased by ~150%, from 46 to 114 MPa, in comparison to the DSS/Al alloy ones.

Microstructure and mechanical properties of Cu/Al joints brazed using(Cu,Ni,Zr,Er)-modified Al−Si filler alloys

To design a promising Al−Si filler alloy with a relatively low melting-point,good strength and plasticity for the Cu/Al joint,the Cu,Ni,Zr and Er elements were innovatively added to modify the traditional Al−Si eutectic filler.The microstructure and mechanical properties of filler alloys and Cu/Al joints were investigated.The result indicated that the Al−Si−Ni−Cu filler alloys mainly consisted of Al(s,s),Al_(2)(Cu,Ni)and Si(s,s).The Al−10Si−2Ni−6Cu filler alloy exhibited relatively low solidus(521℃)and liquidus(577℃)temperature,good tensile strength(305.8 MPa)and fracture elongation(8.5%).The corresponding Cu/Al joint brazed using Al−10Si−2Ni−6Cu filler was mainly composed of Al_(8)(Mn,Fe)_(2)Si,Al_(2)(Cu,Ni)3,Al(Cu,Ni),Al_(2)(Cu,Ni)and Al(s,s),yielding a shear strength of(90.3±10.7)MPa.The joint strength was further improved to(94.6±2.5)MPa when the joint was brazed using the Al−10Si−2Ni−6Cu−0.2Er−0.2Zr filler alloy.Consequently,the(Cu,Ni,Zr,Er)-modified Al−Si filler alloy was suitable for obtaining high-quality Cu/Al brazed joints.

Stirring brazing of dissimilar Al/Mg alloy without flux in air

AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.

Novel approach of LY12 alloy brazing

The LY12 Al alloy was brazed with the adoption of the improved KF CsF AlF 3 flux matching Ag Al Cu Zn filler metal. The shear strength of brazed joint could reach 80% of that of the substrate and the tensile strength of butt brazed joint will be 70% of that of the substrate. This was the great progress against the traditional claim that Al alloy reinforced by heat treatment could not be brazed. The experimental results and theoretical analysis had proved that it was the key issue to remove the MgO oxide film below 503 ℃ . The addition of rare earth La was the effective way to obtain better mechanical properties of the filler metal as well as brazed joints.

Microstructure and Strength of Brazed Joints of Ti_(3)Al Base Alloy with Cu-P Filler Metal

Brazing of Ti3Al alloys with the filler metal Cu-P was carried out at 1173-1273 K for 60-1800 s. When products are brazed, the optimum brazing parameters are as follows： brazing temperature is 1215-1225 K; brazing time is 250-300 s. Four kinds of reaction products were observed during the brazing of Ti3Al alloys with the filler metal Cu-P, i.e., Ti3Al phase with a small quantity of Cu （Ti3Al（Cu）） formed close to the Ti3Al alloy; the TiCu intermetallic compounds layer and the Cu3P intermetallic compounds layer formed between Ti3Al（Cu） and the filler metal, and a Cu-base solid solution formed with the dispersed Cu3P in the middle of the joint. The interracial structure of brazed Ti3Al alloys joints with the filler metal Cu-P is Ti3Al/Ti3Al（Cu）/TiCu/Cu3P/Cu solid solution （Cu3P）/Cu3P/TiCu/Ti3Al（Cu）/Ti3Al, and this structure will not change with brazing time once it forms. The thickness of TiCu＋Cu3P intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity/to of reaction layer TiCu＋Cu3P in the brazed joints of Ti3Al alloys with the filler metal Cu-P are 286 kJ/mol and 0.0821 m2/s, respectively, and growth formula was y2=O.O821exp（-34421.59/T）t.Careful control of the growth for the reaction layer TiCu＋Cu3P can influence the final joint strength. The formation of the intermetallic compounds TiCu＋Cu3P results in embrittlement of the joint and poor joint properties. The Cu-P filler metal is not fit for obtaining a high-quality joint of Ti3Al brazed.

Microstructure evolution and mechanical properties of ultrasonic-assisted soldering joints of 2024 aluminum alloys

Ultrasonic-assisted soldering of 2024 aluminum alloys using a filler metal of Zn-5Al alloy was investigated at the temperature of 400 ℃,which is lower than the solution strengthening temperature of Al-Cu alloys.The ultrasonic vibration with power of 200 W and vibration amplitude of 15 μm at the frequency of 21 kHz was applied on the top samples.The ultrasonic vibration promoted the dissolution of Al elements in the base metal.The reduction of volume fraction of the eutectic phases in the bonds was investigated by increasing ultrasonic vibration time.As the ultrasonic vibration time increased from 3 s to 30 s,the volume fraction of the eutectic phase in the bonds decreased from 12.9% to 0.9%,and the shear strength of the joints was up to 149-153 MPa,increased by 20%.The improvement of the mechanical properties of joints was discussed based on the modulus and hardness of the phases in the bonds and the fracture of the joints.

Effect of welding parameters on Al/Ti joint property in electron beam welding-brazing

The electron beam welding-brazing being used to join 5A06 Al alloy to TC4 Ti alloy decreases the formation of brittle intermetallic compound.Experiments were carried out to study the influence of electron beam welding parameters on the tensile strength of welds,based on an orthogonal test and analysis method.The welding parameters include beam current,welding speed,scanning figure,scanning frequency,figure size,beam offset and focus current.The optimum parameters for3 mm 5A06 Al alloy and 2 mm TC4 alloy were as follows：acceleration voltage was 60 kV,beam current was 11 mA,welding speed was 600 mm/min,focus current was 0 mA,scan figure was O,scanning frequency was 1 000 Hz and beam offset was 0.5 mm.The results show that the joints were with good appearance and quality welded by the optimum parameters.The successful joints could be gained and the maximum tensile strength of Al/Ti dissimilar alloy joints could be up to 222.61 MPa using electron beam welding-brazing.

Al-Si-Cu-Ni钎料成分和钎焊温度对高硅铝合金/可伐合金钎焊接头性能的影响

采用甩带工艺制备Al-7.5Si-23Cu-xNi(x取0,0.5,1.0,1.5,2.0,2.5,质量分数/%)箔状钎料,研究了镍含量对钎料组织和性能的影响;利用性能最好的钎料对CE11高硅铝合金和4J29可伐合金进行真空钎焊,分析了钎焊温度(560~600℃)对接头组织、抗剪强度及气密性的影响。结果表明:随着镍含量的增加,钎料的液/固相线变化较小,熔化温度区间较稳定,铸态钎料局部共晶组织增多,柱状晶变粗大,断裂应变和接头的抗剪强度均先升高后降低;当镍质量分数为2.0%时,钎料的熔化温度区间最小,熔点最低,组织均匀,共晶相较多且弥散分布,钎料的韧性和焊接性能最好。当钎焊温度低于570℃时,Al-7.5Si-23Cu-2.0Ni钎料熔化不完全,与母材结合较差;当钎焊温度高于570℃时,钎料与母材间的元素互扩散剧烈,造成硅相聚集,焊缝中出现裂纹。随着钎焊温度的升高,接头的抗剪强度先升后降,焊后泄漏率先降后升。最佳钎焊温度为570℃,此时焊缝与两侧母材结合紧密,元素扩散均匀,接头的抗剪强度最大,气密性最好。

Ti/Al异种合金激光熔钎焊过程气孔形成机制

采用矩形光斑CO2激光为热源,以AlSi12作为填充焊丝进行钛/铝异种合金的激光熔钎焊试验,发现气孔是导致接头失效的一个主要因素。结果表明,钛/铝异种合金激光熔钎焊的气孔缺陷主要是由镁元素的气化所致。光束的偏移量及激光功率是影响气孔产生的主要因素。界面棒状的金属间化合物长度低于10μm时一般不产生气孔,而气孔的直径与焊缝内部的微观组织有关。

Al元素对Zn-Al钎料钎焊2A01铝合金性能的影响

研究了Al元素对Zn—Al钎料钎焊2A01锅合金性能的影响．钎料润湿性试验结果表明，随着钉料中Al元素含量的增加，钎料在2A01铝合金表面的铺展性能提高，Al元素含量为12％（质量分数）时，铺展面积达到最大，继续增加钎料中Al元素含量，铺展性能降低．钎料中Al元素含量在8％～15％范围内时，钎料均具有良好的铺展性能．钎焊接头力学性能试验结果表明，随着钎料中Al元素含量的增加，钎缝中铝基固溶体强化相数量增加，对接钎焊接头强度提高，钎料中Al元素含量为8％时，钎焊接头强度达到最高，继续增加Al厄素含量，钎缝中的枝状共析组织变得粗大，与其周围组织容易产生应力集中，萌生裂纹，对应的钎焊接头强度降低．综合考虑钎料的铺展性能以及钎焊接头力学性能，92Zn-8A1钎料钎焊2A01铝合金性能最佳．

Ti/Al异种合金电弧熔钎焊接头温度场与界面微观组织

采用交流TIG焊电弧与AlSi12焊丝实现了TC4钛合金与LF6铝合金熔钎焊连接,通过有限元软件分析接头温度场,并利用扫描电镜观察接头钎焊界面的微观组织特征.结果表明,接头温度分布极不均匀,钛侧梯度大高温区窄,铝侧梯度小高温区范围广,冷却时高温区逐渐向钛侧偏移.当钨极正对钛钝边时,等温线平行于钎焊界面,温度分布均匀,有利于形成组织均匀的界面反应层.冷体熔钎焊加速了钎焊界面的冷却,降低了钛的溶解量,可抑制金属间化合物的生长.化合物层形貌由空冷时的锯齿状转变为胞状生长.

光斑形式对Ti/Al异种合金激光熔钎焊特性的影响

采用椭圆形和矩形两种光斑形式对Ti/Al异种合金进行了激光填丝熔钎焊的试验研究,分析了不同工艺参数对焊缝成形的影响规律,获得不同热源作用方式下的界面形态规律及其对界面强度的影响。结果表明,采用椭圆形光斑和矩形光斑进行激光填丝熔钎焊均可获得较满意的焊缝成形。其中矩形光斑具有更好的焊接适应性,更容易控制焊缝成形。抗拉强度测试结果表明,椭圆形和矩形光斑接头的最高抗拉强度分别达到铝母材的75%和80%。

Al-Mg-Zn钎料钎焊镁合金AZ31B接头的显微组织和性能

以Al-Mg-Zn钎料对变形镁合金AZ31B进行了高频感应钎焊,分析了变形镁合金AZ31B钎焊接头的显微组织、钎缝物相和力学性能.采用扫描电镜(SEM)、X射线衍射仪(XRD)、X射线能谱分析仪(EDS)等仪器分析了钎焊接头的界面组织及钎缝生成相,测试了接头的强度及形成相的显微硬度.结果表明,在钎焊接头的钎缝中钎料与母材AZ31B发生反应生成离异共晶组织-αMg+-βMg17(Al,Zn)12,母材AZ31B的显微硬度最低,钎缝中的-βMg17(Al,Zn)12相显微硬度最高.对接和搭接接头断口的断裂形式为沿晶脆性断裂,断裂产生在离异共晶组织-αMg+-βMg17(Al,Zn)12中的-βMg17(Al,Zn)12硬脆相处.

一种具有球晶组织的半固态Zn-Al合金钎料

通过熔炼、浇注以及等温热处理的方法制备了具有球晶组织的Zn-Al合金,并采用重熔实验、等温压缩实验和振动辅助半固态钎焊实验研究了半固态Zn-Al合金的固相率与温度的关系、压缩变形行为以及作为钎料的可钎焊性。结果表明:半固态Zn-Al合金在压缩变形时,具有较强的抗变形能力;作为钎料,在钎焊过程中其固相率能控制在(64±5)%范围内,所得钎焊接头中仅在钎缝边缘处界面上有少许氧化膜残留,而其他区域界面上的氧化膜都被彻底去除。

Zn-Al钎料钎焊6063铝合金铺展性能及接头断裂机理分析

研究了Zn-Al钎料钎焊6063铝合金的铺展性能及接头断裂机理.钎料铺展试验表明,随着钎料中铝含量的增加,钎料铺展面积增大,铝含量增至22%(质量分数)时,钎料铺展面积达到最大,继续增加铝含量,铺展面积减小.钎焊接头力学性能试验表明,随着钎料中铝含量的增加,铝基固溶体强化相数量增加,搭接钎焊接头强度提高,铝含量增至22%(质量分数)时,钎焊接头强度达到最高,继续增加铝含量,钎缝内枝状共析组织变得粗大,与其周围组织之间容易产生应力集中,萌生裂纹,钎焊接头强度降低.综合考虑钎料的铺展性能以及钎焊接头力学性能,78Zn-22Al钎料钎焊6063铝合金性能最佳.

快速凝固Al-Si基粉末钎料的研制

设计了系列铝硅基合金钎料,采用超音速气体雾化技术制备了钎料粉末,系统地研究了快凝钎料微观组织和焊接性能,优化出一种具有较高综合性能的钎料合金Al-10Si-5Cu-5Zn-0.3RE。研究表明:Al-10Si-5Cu-5Zn-0.3RE快凝粉末钎料的平均直径为0.11 mm,组织细小,焊接强度达到了95.8 MPa。Zn元素使快凝钎料的熔点显著降低,稀土元素明显改善钎料的润湿性。

Al-Si-Cu-Zn急冷钎料钎焊铝及铝合金的界面结构及强度

采用Al70Si7.5Cu20Zn2.5和Al65Si10Cu20Zn5两种急冷钎料钎焊L2纯铝和6063铝合金,研究钎焊接头的界面微观结构和力学性能。结果表明,急冷钎料钎焊接头由母材、界面区和钎缝中心组成。界面区为αAl固溶体,钎缝中心组织为αAl固溶体+θ(Al2Cu)相+Si相。采用Al65Si10Cu20Zn5急冷钎料钎焊的接头抗剪强度均高于Al70Si-7.5Cu20Zn2.5急冷钎料钎焊的接头强度;匹配氯化物钎剂钎焊的接头强度均高于氟化物钎剂。在相同的工艺条件下,采用急冷钎料钎焊的L2纯铝接头,其抗剪强度都明显高于相应的常规钎料,其增加值在40%左右。

Al-Si-Cu-Zn急冷钎料制备及润湿性

采用单辊急冷装置制备的两种Al-Si-Cu-Zn急冷钎料钎焊纯铝和6063铝合金,研究其熔化特性、相结构及润湿性。试验结果表明:Al70Si7.5Cu20Zn2.5和Al65Si10Cu20Zn5急冷钎料主要由αAl、Si相和θ(Al2Cu)三相组成;Al65Si10Cu20Zn5急冷钎料和Al70Si7.5Cu20Zn2.5急冷钎料相比,固、液相线温度均有所降低,熔化区间更小;在纯铝和6063铝合金上均具有更好的润湿性;Al65Si10Cu20Zn5和Al70Si7.5Cu20Zn2.5急冷钎料和同成分的常规钎料相比,熔化温度降低,熔化区间更窄;在纯铝和6063铝合金上的润湿性均大大提高。