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Images showing the fracture mechanism observed in the composites heat treated at 450 °C where only a layer of Al3Ni was present along the interface. (a) shows a low magnification optical microscopy image of the cross-section of the fracture surface, where residual aluminum is clearly observed on the Al3Ni layer and no sign of fracturing can be seen along the Al3Ni-nickel interface. (b) shows an SEM image combined with EDS color map of the Al3Ni fracture surface and (c) shows the corresponding aluminum fracture surface. The detected aluminum is colored red and nickel blue.
Source publication
In this work, the interface characteristics and resulting bond strength were investigated for roll bonded steel-aluminum composites with nickel interlayers, both after rolling and after post-rolling heat treatments at 400 °C–550 °C. After rolling, only mechanical interlocking was achieved between the steel and nickel layers, which resulted in delam...
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Citations
... As a kind of nickel-based superalloy, the 80Ni20Cr coating is known for its good bonding with the matrix material. Arbo [35] found that the bonding strength of a steel/aluminum composite plate with a nickel interlayer was improved after a rolling heat treatment. The Ni-Cr coating also had good high-temperature oxidation resistance, which meant that adverse effects of the oxide layer on the bonding strength of the steel/aluminum composite plate could be avoided [36,37]. ...
Given the characteristics of a thick steel/aluminum composite plate, such as its large thickness and the significant differences between its components, it is difficult to prepare using direct rolling. Instead, a thick steel/coating/aluminum composite plate may be successfully prepared by combining supersonic flame coating technology with a hot rolling composite process. In this study, the interface shear strength test, SEM, EDS, and other detection methods were applied to investigate the effects of the reduction rate and coating thickness on the interface structure and mechanical properties. The results show that under the condition of single-pass direct rolling, the micro-interface of steel/aluminum is improved with an increase in the reduction rate, but the bonding strength of the interface remains poor. After adding the coating, the thickness of the diffusion layer and the shear strength increase significantly. When the coating thickness is reduced to 0.1 mm, the deformation coordination and shear strength of the composite plate are further enhanced under the combined action of mechanical interlocking and metallurgical bonding. The tensile shear fracture is mainly located at the steel/coating interface. The interfacial shear strength reaches 66 MPa, which exceeds the requirements of the US military standard MIL-J-24445A (SH) for steel/aluminum shear strength. The research results thus support the use of this new method for the simple and efficient production of thick steel/aluminum composite plates.
... These applications require materials that not only enhance performance across various aspects but also preserve the fundamental structural integrity and essential features of the final product [2,3,16,17,20,43,47]. Similar demands exist in stream of automobiles where the reduction of the encompassed weight of the product is prioritized, thereby impacting various aspects such as performance, cost-efficiency, and logistics [7,9,13,15,18,23,30,34,35,42,46] which can be addressed by using dissimilar material combinations. Dissimilar metals are two or more metals that have different chemical compositions, physical properties, and/or melting points. ...
... Processes such as mechanical roll bonding reportedly produce only physical interlocking between the materials which would not suffice the strength achieved through metallurgical bonding such as Recommended for publication by Commission II -Arc Welding and Filler Metals. welding and brazing [13]. Although conventional metal joining methods like diffusion bonding and friction stir welding (FSW) have reportedly produced robust joints of dissimilar metals, their lack of flexibility and resistance to the formation of intermetallic compounds (IMCs) due to vast differences in melting temperatures further diminishes their reliability [17,26,27,41]. ...
... To overcome the above-mentioned drawbacks in conventional metal joining techniques, CMT, a variant of gas metal arc welding, is employed wherein controlled short circuiting through timely retraction of filler wire is employed, leading to welding at low heat input [42,56]. Various research articles have examined a significant number of material combinations, such as aluminum alongside other metals like steel, magnesium, and nickel alloys, while also discussing issues with weldments, particularly the development of brittle intermetallic compounds at the weld interface, a key factor determining joint strength [3,7,8,10,13,19]. For instance, combinations of aluminum (Al)-and magnesium (Mg)-based alloys have attracted a significant spike in interest due to their potential to reduce the overall weight of automobiles while maintaining the structural strength. ...
In modern engineering applications, there is a growing demand for reducing the overall component weight without compromising strength and integrity. This has led to the combined use of multiple materials. Conventionally, various methodologies such as mechanical fastening, friction stir welding, and transition joints have been proposed to join dissimilar metals. It is worth noting that components made of dissimilar metals present several challenges when it comes to metallurgical joining. These challenges arise from the chemical and thermal properties of the metals, which result in the formation of intermetallic compounds at the interfaces and the occurrence of thermal stresses in the joints. Cold metal transfer method employs controlled short circuiting to minimize heat input, making it ideal for dissimilar metal welding. This reduced heat input effectively prevents excessive thermal stress, distortion, and the formation of brittle intermetallic compounds at the joint interfaces. The current work is presented with a view of providing the various process parameters adopted across combinations of dissimilar metals using CMT method, the complications in the fabrication of joints, and the respective counter actions carried out to attain a solid metallurgical bonding between the metals.
... For instance, the intermetallic layer thickness, and type of phases present, can influence the strength of the final joint. 3 The chemical composition of the base materials has been found to influence the formation of intermetallic phases along the joint interface. 4,5 However, the exact mechanism of phase formation and the influence of each element are not well understood. ...
... The Al-Ni system is well established in composite area in metallic laminated composites [112,113]. The growth kinetics of the Ni-Al IMC layer is well coped with the parabolic rate law, according to Arbo et al. [114]. Al 3 Ni forms first and is presumably more relevant for laser welding, due to faster cooling. ...
... Characteristics of different Al x Ni y phases forming at room temperature[88,112,114,[121][122][123][124]. Composition of Ni (in wt.%) varies depending on temperature. ...
Modern industry requires different advanced metallic alloys with specific properties since conventional steels cannot cover all requirements. Aluminium alloys are becoming more popular, due to their low weight, high corrosion resistance, and relatively high strength. They possess respectable electrical conductivity, and their application extends to the energy sector. There is a high demand in joining aluminium alloys with other metals, such as steels, copper, and titanium. The joining of two or more metals is challenging, due to formation of the intermetallic compound (IMC) layer with excessive brittleness. High differences in the thermophysical properties cause distortions, cracking, improper dilution, and numerous weld imperfections, having an adverse effect on strength. Laser beam as a high concentration energy source is an alternative welding method for highly conductive metals, with significant improvement in productivity, compared to conventional joining processes. It may provide lower heat input and reduce the thickness of the IMC layer. The laser beam can be combined with arc-forming hybrid processes for wider control over thermal cycle. Apart from the IMC layer thickness, there are many other factors that have a strong effect on the weld integrity; their optimisation and innovation is a key to successfully delivering high-quality joints.
... Both these phases grow simultaneously from the first stage of their formation. Previous studies have shown [56] that in the case of the Al/Ni diffusion couple, the occurrence of the intermetallics at the interface is correlated to the temperature of annealing. One hour of annealing at 450 • C resulted in the formation of the Al 3 Ni phase only, while at 500 • C, both Al 3 Ni and Al 3 Ni 2 were observed. ...
The paper presents the microstructure and phase composition of the interface zone formed in the explosive welding process between technically pure aluminum and nickel. Low and high detonation velocities of 2000 and 2800 m/s were applied to expose the differences of the welded zone directly after the joining as well as subsequent long-term annealing. The large amount of the melted areas was observed composed of a variety of Al-Ni type intermetallics; however, the morphology varied from nearly flat to wavy with increasing detonation velocity. The applied heat treatment at 500 •C has resulted in the formation of Al3Ni and Al3Ni2 layers, which in the first stages of growth preserved the initial interface morphology. Due to the large differences in Al and Ni diffusivities, the porosity formation occurred for both types of clads. Faster consumption of Al3Ni phase at the expense of the growing Al3Ni 2 phase, characterized by strong crystallographic texture, has been observed only for the weld obtained at low detonation velocity. As a result of the extended annealing time, the disintegration of the bond occurred due to crack propagation located at the A1050/Al3Ni 2 interface.
... Next, the Ni 2 Al 3 layer was formed at the interface between the NiAl 3 layer and the underlying Ni substrate through the interdiffusion of Ni and Al under a thermal environment so-called Kirkendall effect. 44 The formation of the intermediate layer (Ni 2 Al 3 ) can also be accounted for by its lower formation energy than that of NiAl 3 (NiAl 3 , −0.405 eV; Ni 2 Al 3 , −0.613 45 ). Note that any defects such as the Kirkendall voids were hardly observed at the interfaces of each layer as shown in the cross-section SEM images (Figure 1b), presumably owing to relatively lower the LTCA temperature of 400°C, compared to another Ni−Al foam synthesized at 1024°C accompanied by the Kirkendall voids. ...
We report the fabrication and catalytic performance evaluation of highly active and stable nickel (Ni)-based structured catalysts for ammonia dehydrogenation with nearly complete conversion using nonprecious metal catalysts. Low-temperature chemical alloying (LTCA) followed by selective aluminum (Al) dealloying was utilized to synthesize foam-type structured catalysts ready for implementation in commercial-scale catalytic reactors. The crystalline phases of Ni-Al alloy (NiAl3, Ni2Al3, or both) in the near-surface layer were controlled by tuning the alloying time. The best-performing catalyst was obtained from a Ni foam substrate with a NiAl3/Ni2Al3 overlayer synthesized by LTCA at 400 °C for 20 h. The developed Ni catalyst exhibited an activity enhancement of 10-fold over the nontreated Ni foam and showed outstanding activities of 15 800 molH2molNi-1h-1 (TOF: 4.39 s-1) and 19 978 molH2molNi-1h-1 (TOF: 5.55 s-1) at 550 and 600 °C, respectively. This performance is unprecedented compared with previously reported Ni-based ammonia cracking catalysts with higher-end performance (TOFs of 0.08-1.45 s-1 at 550 °C). Moreover, this catalyst showed excellent stability for 100 h at 600 °C while discharging an extremely low NH3 concentration of 1034 ppm. The NH3 concentration in the exhaust gas was further reduced to 690 and 271 ppm at 700 and 800 °C, respectively, while no deactivation was observed at these elevated temperatures. Through material characterizations, we clarified that controlling the degree of Al alloying in the outermost layer of Ni is a crucial factor in determining the activity and stability because residual Al possibly modifies the electronic structure of Ni for enhanced activity as well as transforming to acidic alumina for increased intrinsic activity and stability.
Diffusion welding of YG8 and 40Cr was carried out by spark plasma sintering. The influence of Ni interlayer with different thicknesses varying from 0 to 500 μm on the welding morphology and mechanical properties of joints was studied. The fracture position moved from the cemented carbide substrate toward the connection interface with the increase in the thickness of the Ni intermediate layer. The joint with nickel-free interlayer and 100-μm thick fractured during electrical discharge machining due to the large residual stress. The bending strength of the joints enhanced with the increase in the Ni intermediate layer from 200 to 300 μm, and a maximum flexural strength of 982 MPa was obtained with the thickness of the Ni intermediate layer to be 300 μm, which was up to 97% of the strength of the cemented carbide substrate. However, the further increase in Ni intermediate layer from 300 to 500 μm resulted in a decrease in the bending strength, which was due to the coupled effects of residual stress and interlayer plastic constraint. Besides, fracture cracks were also observed at the interface of Ni/40Cr with the thickness of Ni intermediate layer to be 400 and 500 μm. The formation of Kirkendall pores in the interface of Ni/40Cr due to different diffusion coefficients of Fe (1.468 × 10−14 m2/s) and Ni (2.15 × 10−14 m2/s) was responsible for the crack initiation and propagation in the Ni/40Cr interface.
The property of fracture toughness is one of the essential parameters in choosing a material that shows resistance to crack growth. In this research, the effect of microstructure evolution on the fracture toughness of Brass (CuZn10)/Low Carbon Steel (St14)/Brass (CuZn10) composite fabricated by the Cold Roll Bonding (CRB) process was investigated. For this purpose, the Brass/Low Carbon Steel/Brass three layered samples were annealed at 450 °C, 600 °C, 750 °C and 850 °C for 2 h. Uniaxial tensile test, microhardness, peeling test, EDS line scan analysis, optical microscope (OM) and scanning electron microscope (SEM) were used to characterize the properties of the composite. The compact tension (CT) test was also used to obtain the fracture toughness of samples. The EDS line scan analysis results showed that no intermetallic compound is formed at the interface of Steel and Brass layers under any temperature. However, increasing the annealing temperature causes the diffusion layer to expand from 5.13 μm to 9.02 μm for samples annealed at 450 °C and 850 °C, respectively, which aids in increasing the bond strength of the layers. Recrystallization changes the layers' microstructure, so the samples' fracture toughness was measured in the roll direction (RD) and transverse direction (TD). It was found that the value of fracture toughness is very different for the as-rolled sample in RD and TD. The most significant decrease in fracture toughness at different temperatures occurs after annealing at 600 °C, wherein the direction of RD compared to the temperature of 450 °C, more than 35% decline was recorded. In fact, after rolling, the microstructure of the layers is elongated in the direction of rolling, which makes the force-crack mouth opening in different directions not the same. Furthermore, as the temperature increases and full recrystallization occurs, the grains become equiaxed, which in addition to reducing the fracture toughness, also reduces the sensitivity to the rolling direction. Based on the obtained results, it was found that the temperature of 600 °C can be chosen as the optimal annealing temperature for three layers of Brass/Steel/Brass composite, in which the appropriate mechanical properties and fracture toughness can be obtained.
A finite element model for the tension and bending of steel/aluminum/steel and aluminum/steel/aluminum three-layer symmetrical composite panels is established using the finite element simulation software ABAQUS to explore the delamination mechanism and influencing factors of the impacted composite interface. Analysis of the stress change law of each layer of the composite panels shows that during failure, necking changes the distribution of the matrix stress on both sides, the steel layer is the first to neck and fracture because it loses the restraint of the aluminum layer. Furthermore, the results reveal an interesting relationship, where the strength of the interfacial bond determines the delamination sequence of the composite plate matrix, resulting in a fracture with a cross-x or step-like morphology. The correctness of the simulation and analysis results is verified by tension and bending experiments in the laboratory.
