Interface microstructure of diffusion bonded Ni3Al intermetallic alloy and austenitic stainless steel

The diffusion bonding of a Ni₃Al intermetallic alloy to an austenitic stainless steel has been carried out at temperatures 950, 1000 and 1050 °C. The influence of bonding temperature on the microstructural development and hardness across the joint region has been determined. The microvoids in the interface have been found to decrease with increasing bonding temperature. The intermetallic phase Al₃Ni has been detected at the Ni₃Al side of the diffusion couple. Diffusion of Cr and Fe from the stainless steel to the Ni₃Al alloy has been observed.     

Interfacial microstructures and properties of aluminum alloys/galvanized low-carbon steel under high-pressure torsion

A new composite processing technology characterized by hot-dip Zn–Al alloy process was developed to achieve a sound metallurgical bonding between Al–7 wt% Si alloy (or pure Al) castings and low-carbon steel inserts, and the variations of microstructure and property of the bonding zone were investigated under high-pressure torsion (HPT). During hot-dipping in a Zn–2.2 wt% Al alloy bath, a thick Al₅Fe₂Zn_x phase layer was formed on the steel surface and retarded the formation of Fe–Zn compound layers, resulting in the formation of a dispersed Al₃FeZn_x phase in zinc coating. During the composite casting process, complex interface reactions were observed for the Al–Fe–Si–Zn (or Al–Fe–Zn) phases formation in the interfacial bonding zone of Al–Si alloy (or Al)/galvanized steel reaction couple. In addition, the results show that the HPT process generates a number of cracks in the Al–Fe phase layers (consisting of Al₅Fe₂ and Al₃Fe phases) of the Al/aluminized steel interface. Unexpectedly, the Al/galvanized steel interface zone shows a good plastic property. Beside the Al/galvanized steel interface zone, the microhardnesses of both the interface zone and substrates increased after the HPT process.     

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。     

Zn层添加AZ31/7075合金复合成形工艺及组织与性能研究EI北大核心CSCD

通过在异种材料界面添加厚度为100μm的Zn箔,采用预挤压与孔型轧制复合工艺成功制备出AZ31/7075复合材料,并利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)对复合界面进行表征及显微硬度测试,探究Zn过渡层在挤压复合孔型轧制过程中对产品的影响。结果表明:7075硬质铝合金芯部可细化AZ31镁合金,引入Zn过渡层可减少或者避免镁铝系金属间化合物生成;挤压及变形温升使Mg-Zn互扩散形成的低熔点共晶相熔化,同时加速元素自固相向液相扩散;然而降温冷却使Mg-Zn扩散层易出现不连续裂缝,但后续孔型轧制可显著改善;Mg-Zn扩散层经变形生成的MgZn_(2)金属间化合物具备较高的显微硬度(161HV),但Mg-Zn扩散层变形后厚度则较薄,结合层整体硬度变化不明显。     

Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot welds

Defect-free dissimilar Al/zinc coated steel and Al/AlSi coated steel welds were successfully fabricated by refill friction stir spot welding. However, Al alloy and uncoated steel could not be welded under the same welding condition. Al-Zn eutectic layer formed at the Al/zinc coated steel interface showed non-uniformity in thickness and nanoscale intermetallic (IMC) produced was discontinuous. The bonding formation between the Al-Zn layer and the surrounding materials was attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface was attributed to a solid/solid reaction mechanism, as the joining process did not involve with melting of base metals or AlSi coating materials. Kissing bond formed at the weld boundary acted as a crack initiation and propagation site, and the present study showed that weld strength of Al 5754/AlSi coated steel was greatly influenced by properties of original IMC layer.     

热输入对AZ31B镁合金/PRO500超高强钢TIG熔-钎连接特性的影响

利用TIG电弧作为热源开展了AZ31B镁合金与超高强钢PRO500熔-钎连接试验,研究了不同焊接热输入条件对接头微观结构及力学性能的影响。结果表明:利用TIG电弧能够实现AZ31B镁合金/PRO500钢的有效熔-钎连接,强度可达镁合金母材的85%,接头界面区形成由Fe-Mg-O化合物、金属间化合物AlFe_3相和基体Fe元素、熔敷金属中扩散过来的Mg元素等共同组成的过渡区;随着焊接电流的增大,AZ31B镁合金/PRO500钢熔-钎焊接头断裂模式由包含了延性断裂和准解理断裂的混合断裂模式转化为准解理断裂主导的脆性断裂模式,结合强度显著下降。     

MB2-LY12扩散焊接头界面组织结构及其形成机制

采用真空扩散焊接技术进行镁合金（MB2）与铝合金（LY12）的焊接,采用超声波无损检测,电子探针、X射线衍射和扫描电镜等手段研究了焊接温度对焊接接头界面附近组织结构的影响,分析了界面反应物的生成机理。结果表明,随着焊接温度的升高,焊接界面的焊合率提高,在焊接压力为3 MPa、保温时间为100 min的条件下,温度升高到480℃完全焊合,在Al侧和Mg侧分别形成了A1（ss,Mg）和Mg（ss,A1）固溶体,焊接界面形成了Al₁₂Mg₁₇、AlMg、Al₃Mg₂三种金属间化合物层,其厚度随着焊接温度的升高而增加,其中AlMg层厚度增长得最快,接头断裂发生在金属间化合物层且呈阶梯状断裂。界面扩散区的形成主要由有效物理接触阶段、固溶体形成阶段、金属间化合物相形成阶段以及金属间化合物增长阶段组成。     

Investigation on diffusion bonding characteristics of SiC particulate reinforced aluminium metal matrix composites (Al/SiCp-MMC)

Joining characteristics of SiC particulate reinforced aluminium metal matrix composites (Al/SiC_p-MMC) were investigated by vacuum diffusion bonding process. The joining performances of the similar and dissimilar composites were studied, and the influences of SiC_p volume percentage and the insert alloy layer on bonding quality and properties of the bonded joints were also estimated. The experimental results indicate that the strength of vacuum diffusion bonded joints decreases with increasing SiC_p volume percentage, and obtaining satisfactory bonding quality in the diffusion bonded joints of the dissimilar Al/SiC_p-MMC is much more difficult than that of the similar Al/SiC_p-MMC. Moreover, the results still manifest that the diffusion bonding either for the similar or for the dissimilar Al/SiC_p-MMC, the suitable insert alloy layer can improve evidently the joining quality of joints, and the strength of diffusion bonded joints corresponding to using the insert alloy layer is apparently higher than that of no insert layer.     

金属镀层对铝/钢激光熔钎焊接头组织与性能的影响

针对在铝/钢焊接过程中,钢的表面金属镀层对铝/钢激光熔钎焊接头性能有着重要影响的问题,研究铝合金在不同金属镀层的低碳钢表面的铺展效果,通过SEM对不同金属镀层下熔钎焊接头界面微观组织形态、金属间化合物厚度、种类等进行分析,并进一步研究不同金属镀层下铝/钢接头的力学性能及断口形貌。结果表明:钢表面的金属镀层对铝/钢激光熔钎焊过程中5A06铝合金在钢上的铺展与浸润有着较大的影响,其中5A06铝合金在镀铝钢上的铺展效果最佳,且铝合金与镀铝锌钢熔钎焊的接头抗拉性能最好,达到母材铝合金的70%。铝/钢界面金属间化合物主要由铝铁金属间化合物组成,其中在镀铝钢、镀铝锌钢、镀锌钢中主要存在Fe2Al5,FeAl3,FeAl等金属间化合物,在镀镍钢界面中还存在Fe4Al13等金属间化合物。     

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。     

Vacuum hot roll bonding of titanium alloy and stainless steel using nickel interlayer

Abstract

Vacuum hot roll bonding of titanium alloy and stainless steel using a nickel interlayer was investigated. No obvious reaction or diffusion layer occurs at the interface between stainless steel and nickel. The interface between titanium alloy and nickel consists of an occludent layer and diffusion layers, and there are the intermetallic compounds (TiNi₃, TiNi, Ti₂Ni and their mixtures) in the layers. The total thickness of intermetallic layers at the interface between titanium alloy and nickel increases with the bonding temperature, and the tensile strength of roll bonded joints decreases with the bonding temperature. The maximum tensile strength of 440·1 MPa was obtained at the bonding temperature of 760°C, the reduction of 20% and the rolling speed of 38 mm s^–1.     

搅拌摩擦焊辅助Al/Zn/Mg接头扩散连接

对2mm厚的AZ31B镁合金和6061铝合金平板进行添加夹层Zn的搅拌摩擦诱导扩散连接实验。通过SEM,EPMA,XRD,拉伸实验和维氏硬度测试研究Al/Zn/Mg搭接接头显微组织和力学性能。结果表明:当旋转速率合适时,扩散层存在Al富集区,Al5Mg11Zn4层及Mg-Zn共晶区;而旋转速率较低时,扩散层存在残留的Zn层;旋转速率过大时,扩散层出现Al-Mg系金属间化合物。由于扩散层主要为金属间化合物,其显微硬度明显高于母材。Zn箔的加入提高了Al/Mg搭接接头的力学性能。断口观察分析表明,接头失效发生在靠近Al侧的扩散层上。     

Laser-tungsten inert gas hybrid welding of dissimilar metals AZ31B Mg alloys to Zn coated steel

Laser-tungsten inert gas (TIG) hybrid welding has been developed for joining Mg alloys to Zn coated steel in a lap joint configuration. The joint could not be produced in laser or arc welding only, while acceptable joints without obvious defects were obtained with a relatively wide processing window in the hybrid process. Two reaction layers were observed to form at the interface and were identified as Mg–Zn eutectic structure (α-Mg + MgZn) and Fe₃Al phase by TEM analysis. In some cases, Al₆Mn phase also formed adjacent to the Fe–Al reaction layer. The tensile-shear strength attained the maximum value of 68 MPa, representing 52.3% joint efficiency relative to Mg base metal. The element Al from AZ31B Mg alloys diffused to the liquid/solid interface and then reacted with the elements from steel, such as Fe and Mn, contributing to the metallurgical bonding at the interface. The weak bonding between Mg–Zn reaction layer and newly formed Fe–Al layer resulted in the interfacial failure.     

Cast joining of cast iron to aluminium casting matrix

Abstract

The present study focused on reinforcing Al–Si–Cu alloy with a cast iron insert and using Zn–xAl–3Si–0·5Mg (wt-%) intermediate alloys by the cast joining technique to take advantage of lightness and stiffness of the hybrid structure. The experimental set-up consisted of coating the insert using hot dipping method followed by immersing the coated insert into the Al melt and allowing the system to cool down to the room temperature. The quality of Al–Fe joints in terms of morphology, thickness, chemistry and microhardness was evaluated as a function of coating composition and immersion time in the Al melt. Characteristics of reaction layer at the coating/insert interface and its effects on the joint properties were determined using microstructural analysis and thermodynamic calculations. Combination of a suitable coating containing 27 wt-%Al and optimised process parameters, including 1 min immersion time, resulted in the formation of an Al–Fe joint with promising characteristics.     

Diffusion bonding between Ti–6Al–4V alloy and ferritic stainless steel

In the present study, Ti–6Al–4V alloy was diffusion bonded to a ferritic stainless steel. The effect of bonding temperature on the microstructural development across the joint region was investigated. After diffusion bonding, microstructural analysis including metallographic examination, energy dispersive spectrograph (EDS) and shear strength was conduced. From the results, it was seen that bonding on the temperature was affecting the Fe and Ti mutual diffusion which controls the interface microstructure. The microstructure of the interface region was formed, consisting of Fe and Ti intermetallics.     

冷金属过渡条件下AZ61镁合金在两种钢板上的润湿行为

采用动态座滴法研究冷金属过渡条件下,AZ61镁合金分别在Q235钢板和镀锌钢板表面的润湿行为及其界面微观结构。结果表明:润湿行为与焊接工艺参数中的送丝速率密切相关;无论基板采用镀锌钢还是Q235钢在界面处均观察到Al-Fe金属间化合物层,其形成符合热力学形成条件;在Q235钢表面润湿时,送丝速率增加,界面反应变得剧烈,因而润湿性变好,在镀锌钢表面润湿时,送丝速率增加,加剧锌的挥发,使裸露的表面显金属性,因而润湿性变好;当送丝速率≤10.5m·min~(-1)时,镁在Q235钢板上的润湿性要好于镀锌钢板,且后者锌的挥发将导致工艺不稳定。     

Si、Sn、Mg对Q235钢在铝浴中腐蚀行为的影响

为降低钢在铝液中的腐蚀,通过对比纯铝、Al-Si、Al-Sn、Al-Mg铝合金熔体静态腐蚀作用下Q235钢/熔体界面的结构、形貌和腐蚀速率,研究了Si、Sn、Mg元素对Q235在铝合金熔体中静态腐蚀的影响。结果表明:Q235在不同铝合金熔体中均发生腐蚀,表面均形成Fe_2Al_5金属间化合物层,在铝液中添加Si可以使形成的Fe_2Al_5层由舌状转变为平板状,减小Fe_2Al_5层厚度,并显著减缓腐蚀速率;添加Sn和Mg不改变Fe_2Al_5层的形态和厚度,减缓腐蚀速率效果不如Si显著;Si、Sn、Mg不改变Fe_2Al_5择优生长的特点;Si降低腐蚀速率的机制是阻塞Fe_2Al_5空位孔道抑制原子扩散;Sn、Mg降低腐蚀速率的机制是占位阻隔减缓扩散速率。     

Technique of Aluminum Alloy Composite by Inversion Casting

The influence of the temperature of liquid aluminum alloy,the dipping time in liquid alloy and the thickness of base strips on the solidified layer was studied during the process of producing aluminum alloy composite strips used in automobile radizator with inversion casting.It is concluded that there is welding as well as diffusion of alloying elements between the base strip and the coating.Experiments proved that the interface has a good bonding.     

Analysis of process parameters effects on friction stir welding of dissimilar aluminum alloy to advanced high strength steel

Thin sheets of aluminum alloy 6061-T6 and one type of Advanced high strength steel, transformation induced plasticity (TRIP) steel have been successfully butt joined using friction stir welding (FSW) technique. The maximum ultimate tensile strength can reach 85% of the base aluminum alloy. Intermetallic compound (IMC) layer of FeAl or Fe₃Al with thickness of less than 1 μm was formed at the Al–Fe interface in the advancing side, which can actually contribute to the joint strength. Tensile tests and scanning electron microscopy (SEM) results indicate that the weld nugget can be considered as aluminum matrix composite, which is enhanced by dispersed sheared-off steel fragments encompassed by a thin intermetallic layer or simply intermetallic particles. Effects of process parameters on the joint microstructure evolution were analyzed based on mechanical welding force and temperature that have been measured during the welding process.     

Effect of gradient thermal distribution on butt joining of magnesium alloy to steel with Cu–Zn alloy interlayer by hybrid laser–tungsten inert gas welding

Experimental investigations on butt welding of magnesium alloy to steel by hybrid laser–tungsten inert gas (TIG) welding with Cu–Zn alloy interlayer are carried out. The results show that the gradient thermal distribution of hybrid laser–TIG welding, controlled by offset adjustment, has a noticeable effect on mechanical properties and microstructure of the joints. Particularly, at the offset of 0.2 mm, defect-free joints are obtained, and the tensile strength could attain a maximum value of 203 MPa. Moreover, the fracture of the joint with the 0.2 mm offset happens in the weld seam of Mg alloy instead of the Mg/Fe interface. Owning to the addition of the Cu–Zn alloy interlayer, a metallurgical bonding between Mg alloy and steel is achieved based on the formation of intermetallic compounds of CuMgZn and solid solutions of Cu and Al in Fe. Meanwhile, the same element distribution tendency of Fe and Al indicates the intimate interaction between Fe and Al in current experimental conditions.