不锈钢／Al固液轧制复合板材界面的精细结构

应用场发射透射电子显微镜研究了不锈钢／Ａｌ固液轧制复合板材界面的精细结构。结果表明,在钢－Ａｌ之间存在主要由两种金属间化合物组成的界面反应层。靠近钢处由一层细小的（Ｆｅ,Ｃｒ,Ｎｉ）２Ａｌ５纳米晶组成,靠近Ａｌ处由纳米级的（Ｆｅ,Ｃｒ,Ｎｉ）４Ａｌ１３柱状晶组成。反应层附近的Ａｌ中有各种形态的（Ｆｅ,Ｃｒ,Ｎｉ）４Ａｌ１３相析出,并对界面结构的形成进行了初步的分析。     

Al-Fe金属间化合物对复合板界面结合的影响(英文)

对固态铝和固态铁界面金属间化合物的生长及金属间化合物对界面结合的影响进行了研究。结果表明,固态铝和固态铁热处理后的界面主要包括Fe2Al5和FeAl3化合物层,金属间化合物恶化了界面结合强度。在拉剪测试中,断裂主要发生在Fe2Al5或FeAl3化合物层,断裂的位置主要取决于化合物层内部的缺陷,包括微裂纹和空洞。热膨胀系数不匹配产生的应力导致内部微裂纹产生,内部孔洞产生的原因是Kirkendall效应。该研究对铝和铁的焊接与连接,尤其是对铝钢复合板的制备,奠定了一定的基础。     

H13热作模具钢微弧氧化复合陶瓷层的组织和性能

通过热浸镀铝/微弧氧化复合工艺对H13模具钢进行表面改性以提高模具表面质量。在热浸镀铝过程中,将H13钢基体浸入710℃纯铝液6 min,得到了以Fe2Al5为主中间合金层,使得镀层与基体紧密结合。经过微弧氧化处理后,镀铝试样表面铝层转化为氧化铝陶瓷,主要由α-Al2O3和γ-Al2O3相组成。用带有能谱分析装置(EDX)的扫描电镜(SEM)、X射线衍射(XRD)分析了膜层的形貌、成分和相组成。微弧氧化陶瓷层主要由Al、O、Si元素组成,其中O、Si主要来源于硅酸盐电解液。     

镀液合金元素对钢镀铝界面组织的影响

研究了钢铁热浸镀镀液中添加不同元素对合金层生长的影响,检测了镀层的形貌和结构并分析了合金层形成和生长的机理.结果表明,镀层由表面的浸铝层和内层的合金层构成;合金层由Fe2Al5和FeAl3等Fe-Al金属间化合物组成;Si的添加能有效抑制合金层的生长,Mn与Mg的作用不明显,Zn则加剧了合金层的生长;合金层的生长随时间近似遵循抛物线关系.     

Analysis of Intermetallic Phases Formed on Surface Vapor Oxidized H13 Hot Work Steels in Molten Aluminum

In this paper, the author dipped surface vapor oxidized H13 steel specimens into 700℃ molten aluminum liquid for a certain period of time. Analyze the intermetallic phases formed on the H13 samples surface with optical microscope and X-ray diffraction method. The observation of immersion test sample's cross-section shows that Fe3O4 film will protect die substrate from molten aluminum erosion. The identification of the intermetallic phases reveals that they consist of 2parts, which is named as the composite layer and the compact layer. Further investigations are made in order to know the phase constituents of the 2 layers, they are Al8Fe2Si (outer composite layer), (AlCuMg) and Al5Fe2 (compact layer),respectively. The experimental results show that on the same specimen, a convex surface with bigger radius of curvature is more likely to be molten and the melting loss speed is also faster than a flat and smooth surface. The thickness of compact layer on a smooth surface is much bigger than that of the convex surface. Therefore, the author supposes the compact layer is favorable in stabilizing the die surface material from further melting loss, as their formation on the die surface, the melting loss speed will decrease.     

Melt flow in a mushy zone – barrier effect of intermetallic phases

Abstract

Iron and manganese are common impurity elements in cast aluminium alloys, especially in secondary aluminium. During casting Fe/Mn-containing intermetallics are formed between the aluminium dendrites, which cause porosity and shrinkage defects. In this paper an experimental study on the influence of controlled convection during solidification on the spatial arrangement of intermetallic phases and their interaction with the dendritic microstructure in Al–7Si–1Fe (AlSiFe) and Al–7Si–1Mn (AlSiMn) alloys (wt-%) is presented. Forced convection is induced by a rotating magnetic field. The alloys are solidified directionally over a range of constant solidification velocities (0·015–0·18 mm s^–1) at a constant temperature gradient G of 3 K mm^–1. The results indicate that the primary spacing and the secondary dendrite arm spacing are affected by the presence of Fe and Mn intermetallic phases. In samples solidified under forced convections the primary dendrite arm spacing did not depend on the solidification velocity and no obvious fluid flow effect on the secondary spacing could be detected. These observations are in contrast to Fe and Mn free alloys. It seems that the intermetallics act as a barrier for the flow into the mushy zone.     

Microstructure Evolution of Hot-Dip Al-10% Si Coating During the Austenitization of 22MnB5 Hot Stamping SteelEI北大核心CSCD

Hot stamping is an alternative technology to produce ultra-high strength steel (UHSS) with a tensile strength above 1 GPa for automotive bodies. At present, the hot-dip Al-10% Si (mass fraction) coating is used as a shield coating for the hot stamping steels, which protects the steels from surface oxidation and decarburization, and enhances their corrosion resistance. However, the microstructure evolution and compounds of hot-dip Al-10% Si coating during austenitization of 22MnB5 hot stamping steel are not clear yet. In this work, the thermo-mechanically induced microstructure evolution of hot-dip Al-10% Si coating is observed using SEM after austenitization of 22MnB5 hot stamping steel at 900 degrees C for different times, and the elemental depth profiles are analyzed in hot-dip Al-10% Si coating by EDS and GD-OES. The results show that before austenitization, the hot-dip Al-10% Si coating consisted of an aluminum matrix, pure silicon, and the intermetallic compound Fe2SiAl7, which was formed by eutectic reaction, there was a thin layer, which was composed of Fe2Al5 and FeAl3 between the intermetallic compound Fe2SiAl7 and the steel substrate. When 22MnB5 hot stamping steel was austenitized at 900 degrees C, the ternary eutectic phase Al+ Si+ tau(6) was transformed into an Al-Fe-Si ternary intermetallic compound or Fe-Al binary intermetallic compound gradually in the hot-dip Al-10% Si coating. When the austenitizing time was 2 min, the Al-10% Si coating was composed of the intermetallic compound Fe2SiAl7, Fe2Al5 and FeAl2 phases; when the austenitizing time was 5 min, the Al-10% Si coating was composed of FeAl2, Fe2SiAl2 and Fe5SiAl4 phases; when the austenitizing time was 8 min, the Al-10% Si coating was composed of FeAl2 and Fe5SiAl4 phases. Because the diffusion rate of Al atoms was much larger than that of Fe atoms in the diffusion layer of intermetallic compound Fe2SiAl2 and coating/steel substrate, the amount of Al atoms which diffused and reacted from the coating to the grain boundaries or grain of steel substrate was much larger than that of the Fe atoms which diffused from the steel substrate to the Al10% Si coating, also the number of vacancies which diffused from the steel substrate to the Al-10% Si coating was much larger than the other way round. Due to this imbalance, the Kirkendall void was formed in the interface between the diffusion reaction layer and the Al-10% Si the coating. The hot-dip Al-10% Si coating can be used as the protective layer, since it has a stable Al2O3 film formed on its surface, and its thermal oxidation was very limited, during the 22MnB5 hot stamping steel austenitizing. But the protective performances of Al-10% Si coating could be poor, because the high temperature ductility of brittle intermetallic compound was low, which induced a lot of micro cracks that were perpendicular to the interface of coating/steel substrate, and penetrated the whole coating during the diffusion process of hot-dip Al-10% Si coating.     

交流磁场对过共晶Al-2.89%Fe合金中含铁相分布的影响

在交流磁场作用下,过共晶Al-2．89％Fe（质量分数,％）合金中含铁相向样品的中心处富集．这是由于Al3Fe相的磁化率大于熔融铝的磁化率,使得Al3Fe相与铝基体相比受到指向试样轴线处更大的电磁力,从而聚集在试样中心．X射线衍射结果表明,在无磁场和交流磁场条件下,含铁相中只含有A13Fe相．交流磁场改变了析出相的分布,但没有改变析出相的类型．     

Annealing Effect on the Intermetallic Compound Formation of Cold Sprayed Fe/Al Composite Coating

A Fe/Al composite coating was prepared by cold spraying using an iron-aluminium powder mixture with a Fe/Al atomic ratio of 1:1. The effect of annealing temperature on the intermetallic compound formation in the cold-sprayed Fe/Al coating was investigated. The as-sprayed and annealed coatings were characterized by x-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy. Results showed that intensive particle deformation on impact promoted the Fe₂Al₅ intermetallic compound formation at a low annealing temperature of 450?°C and this intermetallic layer firstly appeared along some intimate contact regions at the aluminium-iron boundaries. The amount of the Fe₂Al₅ intermetallic compound increased and no other intermetallic compound phases appeared when the annealing temperature was raised from 450 to 600?°C. Some cracks developed in the Fe₂Al₅ intermetallic layer when the coating was annealed at 600?°C and the possible causes leading to evolution of cracks are discussed.     

Effect of the axial external magnetic field on copper/aluminium arc weld joining

Pure copper and aluminium alloy was joined by cold metal transfer welding with the assistance of an axial external magnetic field in this work. The results reveal that magnetic field led to a reduction of the average heat input and improved the wetting behaviour of the weld metal on the copper sheet surface. The thickness of the Al₂Cu intermetallic compound layer formed at the interface was decreased from 50?µm for normal welding to 5?µm for the magnetic field-assisted welding process. The joint strength was observed to increase with the magnetic field. For a 21?mT and 10?Hz magnetic field, the maximum loading force reached up to 1.67?kN, resulting in an increase in joint strength by 33%.     

Numerical modelling of gas metal arc joining of aluminium alloy and galvanised steels in lap joint configuration

Advanced pulsed current gas metal arc based processes are increasingly attempted for the joining of aluminium alloys and galvanised steel sheets. The bead profile and the thickness of the interfacial Fe–Al intermetallic (IMC) layer significantly influence the failure strength of these joints. Although several experimental studies have examined the nature and extent of the IMC phases and consequent joint strength, quantitative efforts to estimate bead profile and the IMC layer thickness as function of process conditions and resulting heat input are scarce. We present here for the first time a coupled theoretical and experimental study to estimate the bead profile and Fe–Al IMC layer thickness for joining of galvannealed steel and aluminium alloy sheets in a typical lap joint configuration. The computed values of bead profile and IMC layer thicknesses are validated with the corresponding experimental results.     

铝/钛异种金属冷金属过渡熔钎焊接头分析

以ER4043的铝焊丝对6061铝合金和TA2纯钛进行CMT熔钎焊,采用金相显微镜、扫描电镜(SEM)和能谱分析仪(EDS)分析了焊接接头的微观组织特征,并通过拉伸试验对接头进行了力学性能的评定. 结果表明,焊接接头具有熔焊和钎焊双重性质:铝母材局部熔化,与熔化的焊丝金属混合后凝固形成焊缝;而没有熔化的钛母材通过Ti原子的扩散与焊缝金属形成金属间化合物结合层的钎焊界面. 钎焊界面处反应层可分为靠近钛板一侧的连续层Ti₃Al和向焊缝内部生长的锯齿状的反应层TiAl₃. 当钛板坡口角度为30°时,钎焊界面化合物生长均匀良好,接头会断裂在铝母材的热影响区,最高抗拉强度达到197.5 MPa.     

Interface properties and thermodynamic analysis of laser–arc hybrid welded Al/steel joint

Abstract

Fibre laser–cold metal transfer hybrid welding was introduced to join AA 6061 aluminium alloy with AISI 304 stainless steel using Al–12Si filler wire. Interface properties and microstructure of welded joints were observed by optical microscope, scanning electron microscope, energy dispersive spectrometry and X-ray diffraction techniques. A serrated intermetallic compound (IMC) layer was found at the interface between fusion zone and stainless steel. The morphology of IMC layer was uniform from the top to the bottom, and its average thickness was 3 μm. The IMC layer consisted of two layers: Al₈(Fe,Cr)₂Si layer close to fusion zone and (Al,Si)₁₃Fe₄ layer close to stainless steel. The joint fractured at the IMC layer and presented a tensile strength of 165 MPa. The formation of the IMC layer was closely related with the thermodynamic and kinetic behaviours of the interface and fast cooling rate of hybrid welding.     

Morphology and formation of Fe–Al intermetallic layers on iron hot-dipped in Al–Mg–Si alloy melt

We have examined the morphology and the growth of Fe–Al intermetallic layers of η-Fe₂Al₅ and θ-FeAl₃ phases formed on pure Fe sheets dipped in an Al-8.2Mg-4.8Si (wt.%) alloy melt and pure Al melt at 750 °C. The η phase layer grows one order of magnitude slower in the Al–Mg–Si alloy melt than in the pure Al melt. The change in thickness of Fe sheets with dipping time is less pronounced in the Al–Mg–Si alloy melt than in a pure Al melt. Microstructure observations suggest that the retarded interfacial reaction between solid Fe and liquid Al–Mg–Si alloy is associated with a continuous θ phase layer formed in the Al–Mg–Si alloy melt, which acts as the diffusion barrier.     

Analysis of intermetallic layer in dissimilar TIG welding–brazing butt joint of aluminium alloy to stainless steel

Abstract

Intermetallic layer of dissimilar tungsten inert gas welding–brazing butt joint of aluminium alloy/ stainless steel has been studied. A visible unequal thickness intermetallic layer has formed in welded seam/steel interface, and the thickness of the whole layer is <10 μm. The interface with Al–12Si filler metal consists of τ ₅-Al₈Fe₂Si layer in welded seam side and θ-(Al,Si)₁₃Fe₄ layer in steel side with the hardness values of 1025 and 835 HV respectively, while the interface with Al–6Cu filler metal consists of θ-Al₁₃(Fe,Cu)₄ layer with the hardness of 645 HV. The average tensile strength of the joint with Al–12Si filler metal is 100–120 MPa, and the fracture occurs at θ-(Al,Si)₁₃Fe₄ layer, while the joint with Al–6%Cu filler metal presents high crack resistance with tensile strength of 155–175 MPa, which reaches more than 50% of aluminium base metal strength.     

Refining alloy zinc-iron with intermetallic phases ZnnFem by formation phases AlnFem

Results on research work on hard zinc refining with aluminium on a laboratory and a commercial scale have been presented. The research was carried out according to a fractorial experiment design with the determination of four processes variables. Distribution of Al, Fe and Zn was examined by the X-ray micro-analyser and also intermetallic phases were identified. As a result of the formation of intermetallic phases which, lighter than zinc, were coming to the metal surface, a refined zinc containing 0.02 wt.% Fe and suitable for re-use in the processes of steel products coated with zinc, was obtained.     

TiB2金属陶瓷与TiAl金属间化合物的扩散连接

对TiB2金属陶瓷与TiAl金属间化合物进行了扩散连接试验，研究了直接扩散连接和采用Ni为中间层进行扩散连接的接头界面结构及工艺参数对界面结构和连接性能的影响。直接扩散连接时，连接界面处生成了Ti(Cu，Al)2金属间化合物，采用Ni为中间层进行扩散连接时，界面处生成了单层TiAlNi2金属间化合物层和两层T1，Al，N2扩散层共三层结构。直接扩散连接时，连接温度T＝1223K，时间t=1．8ks，压力p＝80MPa时接头强度为103MPa；采用Ni为中间层时，连接温度T＝1273K，时间t=1．8ks，压力p=80MPa时接头强度为110MPa。     

Microstructure of aluminized stainless steel 310 after annealing

The aluminized coating on type 310 stainless steel prepared by high-activity Al pack cementation method has been annealed at 900 °C for 12 h to transform the brittle δ-Fe₂Al₅ phase into the more ductile β-FeAl phase. The microstructure is studied in detail with transmission electron microscopy. The thick outer layer has β-(Fe, Ni)Al as matrix with cube-like Cr₂Al precipitates. The interfacial layer has a thin layer of metastable FCC phase (layer I) and then mixed β-(Fe, Ni)Al grains and α-(Fe, Cr) grains (layers II and III). The Cr₂Al precipitates are present in the β-(Fe, Ni)Al grains in layer II but not in those in layer III, while β-FeAl precipitates are present in the α-(Fe, Cr) grains in both layers. The orientation relationships between various phases, the formation of the layers, and the precipitation of Cr₂Al in β-(Fe, Ni)Al are discussed.     

铝合金/不锈钢预涂层钨极氩弧熔钎焊接头的特性

通过在不锈钢表面预涂钎剂层,采用铝硅共晶钎料实现铝合金/不锈钢TIG熔钎焊连接,获得具有熔焊与钎焊双重性质的对接接头,运用OM、SEM、EDS分析接头的微观组织及成分,通过拉伸实验评定接头的力学性能.结果表明:铝母材局部熔化,与液态钎料混合后凝固形成焊缝,焊缝组织主要由α(Al)基体和在晶界析出的Al-Si共晶相组成;不锈钢不发生熔化,液态钎料与不锈钢在界面反应形成不均匀分布的金属间化合物层,最大厚度不超过10 μm,界面上部金属间化合物较厚,呈锯齿状,主要相成分为α(τ5)-Al7.4Fe2Si;界面下部金属间化合物较薄,呈细须状,由α(τ5)-Al7.4Fe2Si+α(Al)混合相构成;接头的平均抗拉强度为90.6 MPa,焊缝/不锈钢界面下部为连接的薄弱环节,成为断裂的起始位置.     

Microstructures and mechanical properties of AZ91D/0Cr19Ni9 bimetal composite prepared by liquid-solid compound casting

The liquid-solid compound casting technology was used to produce the AZ91D/0Cr19Ni9 bimetal composite without and with hot dipping aluminium, respectively. The influences of Al coating on microstructures and mechanical properties of AZ91D/0Cr19Ni9 interface were investigated. The results showed that the mechanical bonding was obtained between AZ91D and bare steel 0Cr19Ni9 where a gap existed at the interface; the metallurgical bonding was formed between AZ91D and Al-coated 0Cr19Ni9, which could be divided into two different intermetallic layers: layer I was mainly composed of α-Mg+β-Mg₁₇Al₁₂ eutectic structure and a small amount of MgAl₂O₄, and layer II mainly comprised of Fe₂Al₅ intermetallic compound. Furthermore, the hardness value of interface was obviously higher than that of AZ91D matrix, and the average hardness values of layers I and II were HV 158 and HV 493, respectively. The shear strength of AZ91D/Al-coated 0Cr19Ni9 interface was higher than that of AZ91D/bare 0Cr19Ni9 interface, which confirmed that Al coating could improve the adhesive strength between AZ91D and 0Cr19Ni9 during liquid-solid compound casting process.