Distribution Of Intermetallic Compounds Research Articles

In Situ SEM, TEM, EBSD Characterization of Nucleation and Early Growth of Pure Fe/Pure Al Intermetallic Compounds.

The nucleation and growth processes of pure Fe/pure Al intermetallic compounds (IMCs) during heat treatment at 380 °C and 520 °C were observed through in situ scanning electron microscopy (SEM). The size of the IMCs were statistically analyzed using image analysis software. The types and distribution of IMCs were characterized using transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). The results showed that: at 380 °C, the primary phase of the Fe/Al composite intermetallic compounds was Fe4Al13, formed on the Fe side and habituated with Fe. The IMC was completely transformed from the initial Fe4Al13 to the most stable Fe2Al5, and the Fe2Al5 was the habitus with Fe during the process of holding at 380 °C for 15 min to 60 min. At 380 °C, the initial growth rate of the IMC was controlled by reaction, and the growth rate of the thickness and horizontal dimensions was basically the same as 0.02-0.17 μm/min. When the IMC layer thickness reached 4.5 μm, the growth rate of the thickness changed from reaction control to diffusion control and decreased to 0.007 μm/min. After heat treatment at 520 °C (≤20 min), the growth of IMC was still controlled by the reaction, the horizontal growth rate was 0.53 μm/min, the thickness growth rate was 0.23 μm/min, and the main phase of the IMC was the Fe2Al5 phase at 520 °C/20 min.

Ti-Cu積層造形合金における熱処理による析出形態の制御と機構解明

Intermetallic compounds (IMCs), known for their hardness, play an important role in the precipitation strengthening of alloys. However, precipitation in excessive amounts or as large particles can result in embrittlement of the material. Thus, controlling the distribution of IMCs among the matrix is crucial for the design of strong and ductile alloys. In this research, a supersaturated Ti-Cu alloy formed by Laser Powder Bed Fusion (L-PBF) was heat-treated at different phase regions to produce lamellar, network, and dispersed distributions of Ti2Cu IMC precipitates. To comprehensively understand the formation mechanisms of each IMC distribution structure, in-situ microstructure observation was performed during the heat-treatments. The lamellar IMC structure obtained from heat treatment above the beta-transus temperature, was found to derive from the rejection of Cu atoms towards the boundaries of lamellar alpha grains formed during cooling. The network IMC structure obtained from heat-treatment in the α+β phase region involved the formation of a Cu-rich β-Ti layer between α-Ti grains during heating, and subsequent precipitation of Ti2Cu into an α-encapsulating network upon cooling. Finally, the dispersed structure of IMCs was observed to result from regular nucleation and growth of Ti2Cu during heat treatment in the α+IMC region.

Investigation on the microstructure, mechanical and electrical properties of Ti3SiC2/Cu joint obtained by Ti25Zr25Ni25Cu25 amorphous high entropy alloy and Ag composite filler

Ti3SiC2/Cu brazed joint has an important application in the pantograph of high-speed trains, but excessively continuous intermetallic compounds (IMC) and thick diffusion reaction zone (DRZ) in the joint are detrimental to both the mechanical and electrical properties of the joint. Therefore, regulating the interfacial microstructure is an effective way to acquire an excellent brazed joint. In this study, Ti25Zr25Ni25Cu25 amorphous high entropy alloy (HEA) was fabricated, and the brazing of Ti3SiC2 to Cu was carried out by the Ti25Zr25Ni25Cu25 HEA and Ag foil composite filler. The hysteresis effect of the HEA effectively slowed down the interfacial atomic diffusion and metallurgical reactions, which is conducive to the formation of relatively thin DRZ. Due to the combination of Ag foil and the HEA, the IMC distribution in the joint obtained at a relatively low temperature is more dispersed and uniform. Under the optimal brazing conditions, the maximum shear strength of the brazed joint obtained with the Ti25Zr25Ni25Cu25 and Ag composite filler is 34.85% higher than that obtained with Ag-26.7Cu-4.5Ti conventional filler. In particular, the electrical resistance of the joint obtained with the composite filler is 20.35% lower than that obtained with the single Ti25Zr25Ni25Cu25 HEA filler.

Microstructure and mechanical properties of a GH3536/SS304 joint brazed with a Co25Fe25Mn5Ni25Ti20 eutectic high-entropy alloy filler

To realize a high-strength connection between dissimilar metals, a eutectic high-entropy alloy (EHEA), Co25Fe25Mn5Ni25Ti20 was used as a novel filler to braze GH3536 and SS304. Its typical microstructure and evolution mechanism were investigated, and its mechanical properties were also evaluated. The results showed that under the influence of the high-entropy effect, a large amount of a (Fe, Co, Ni)-rich face-centered cubic solid solution formed and became the main component of the seam. On the other hand, only a small amount of Ti-based intermetallic compounds (IMCs) existed in the seam, ensuring a high-quality joint. The interfacial microstructure was affected by the brazing temperature because the reaction degree and high-entropy effect changed simultaneously, as did the distribution of IMCs in the matrix, which significantly affected the mechanical properties. The maximum shear strength reached 568 MPa when the joint was brazed at 1180 °C for 10 min. This study proposed a novel approach for connecting dissimilar metals, thus increasing the potential of EHEAs as fillers.

Coupling effect of axial ultrasonic vibration and tool thread on the microstructure and properties of the friction stir lap welding joint of Al/Mg dissimilar alloys

In this study, three tools with different thread characteristics were designed for the ultrasonic-assisted friction stir lap welding (UAFSLW) of a 3-mm-thick 6061-T6 aluminum alloy and an AZ31 magnesium alloy. The coupling effect of different thread characteristics and axial ultrasonic vibrations on the size, amount, and distribution of intermetallic compounds (IMCs) and the tensile-shear strength of welded joints was analyzed. Experimental results confirmed the formation of IMCs in the stir zone (SZ) and the bottom interface in the SZ in all joints, with Al3Mg2 predominating in the Al-Mg configuration (in which the 6061-T6 aluminum and AZ31 magnesium alloys were placed at the upper and lower plates, respectively) and Al12Mg17 predominating in the Mg-Al configuration (in which the alloys on the upper and lower plates were reversed). The bottom interfaces of the joints in the Mg-Al configuration were tortuous, forming a mechanical interlocking structure; consequently, the joints welded in the Mg-Al configuration exhibited higher tensile-shear strength than those welded in the Al-Mg configuration. Furthermore, the tool with a variable-pitch thread pin achieved welds with excellent tensile-shear strength in both the configurations (223.2 and 268.3 N/mm in the Al-Mg and Mg-Al configurations, respectively). This performance improvement was attributed to the strong coupling of the tool with axial ultrasonic vibrations, which enlarged the mixing zone and increased the uniformity of the IMCs distribution in the joints.

Homogenizing the intermetallic compounds distribution in Al/Cu dissimilar friction stir welding joint with the assistance of ultrasonic vibration

In this work, plates of dissimilar Al/Cu alloys were butt jointed by friction stir welding (FSW) with and without ultrasonic vibration. It was found that the assistance of ultrasonic vibration produced slight variations of both mechanical interlocking and material intermixing of dissimilar material, as well as fracture location during tensile tests, but it particularly reduced the thickness of intermetallic compounds (IMCs) layer in the middle part of the Al/Cu joint. Therefore, by homogenizing the IMCs distribution along the bonding interface within a thickness of 1.0 µm, the tensile strength of the Al/Cu FSW joint was improved from 195.5 to 215.0 MPa with the assistance of ultrasonic vibration.

Microstructure and Mechanical Properties of Aluminum Alloy/Stainless Steel Dissimilar Ring Joint Welded by Inertia Friction Welding

In recent years, studying the weldability of a dissimilar metal hybrid structure, with the potential to make full use of their unique benefits, has been a research hotspot. In this article, inertia friction welding was utilized to join Φ130 forged ring of 2219 aluminum alloy with 304 stainless steel. Optical observation (OM), electron back scattering diffraction (EBSD), and scanning electron microscopy (SEM) were utilized to examine the joint microstructure in depth. Depending on the research, a significant thermal–mechanical coupling effect occurs during welding, resulting in inadequate recrystallization on aluminum-side thermo-mechanically affected zone (TMAZ) and forming zonal features. The crystal orientation and grain size of each TMAZ region reflect distinct differences. On the joint faying surface, the growth of intermetallic compounds (IMCs) is inhibited by a fast cooling rate and metallurgical bonding characteristics were found depending on the discontinuous distribution of IMCs. The average joint tensile strength can reach 161.3 MPa achieving 92.2% of 2219-O; fracture occurs on aluminum-side base metal presenting ductile fracture characteristics.

Effect of beam oscillation on intermetallic compounds and mechanical properties of steel/aluminum laser welded joint

Brittle Fe-Al compounds limit the performance of the steel/aluminum joint. Beam oscillation laser technology was performed to control the thickness, morphology and distribution of intermetallic compounds (IMCs) at interface. The results showed that beam oscillation significantly reduced the thickness of IMC layer. When oscillation frequency was 10 Hz, the needle-like phase embedded in aluminum matrix was obviously passivated in the circular oscillation mode, while the needle-like phase at interface tend to distribute parallel to the layer-like IMC, and formed a “bite” connection effect with aluminum matrix. In the linear oscillation mode, the needle-like phase disappeared, and smooth and flat interface was obtained. Compared with the non-oscillation mode, in the case of circular or linear oscillation mode, the width of molten pool was significantly increased, the crystal grains were refined, and the joint property was increased by 26% and 17% respectively, which were caused by the combined effect of mechanical bonding and metallurgical regulation. The influence mechanism of beam oscillation on the thickness, morphology and distribution of IMC at interface was revealed by high-speed photography and finite element simulation, which provides a new idea for the welding of steel/aluminum dissimilar materials.

Progress on microstructure features and creep properties of prospective Tin-Silver-Zinc alloy using a magnetic field

In the current work, applying a rotating magnetic field (RMF) is an innovative approach to improve the microstructure features and creep resistance of Sn-2.0Ag-2.0Zn (SAZ) alloy. The results revealed that RMF does not change intermetallic compounds (IMCs) constituents furthermore SAZ alloy with applying a magnetic field (SAZ-B) exhibited microstructure refinement and homogeneous distribution of IMCs. Moreover, SAZ-B displayed more creep resistance (∼366%) and greater creep rupture time (∼56.4%) than those of SAZ alloy. These results have great implications in improving the alloy’s performance for industrial applications.

Study of plastic flow on intermetallic compounds formation in friction welding of aluminum alloy to stainless steel

During friction welding of Al alloy to steel, the metallurgical reaction of Al and Fe can be occurred under the coupling effect of heat and rotational plastic flow. However, the detailed role of them in contributing intermetallic compounds (IMCs) development remains largely unknown, causing the significant impediment in further tailoring IMCs. In this regard, a thermal compression bonding process was elaborately designed to highlight the influence of frictional flow on the formation of IMCs in friction welding. From the results, it was revealed in friction welding process, frictional flow significantly promoted the formation of sub-micron sized IMCs along weld interface, since in thermal compression bonded specimens, a significantly thinner IMCs were confirmed. Due to the non-uniform distribution of heat and plastic flow rate at different regions along interface, an inhomogeneous distribution of IMCs in terms of thickness was also identified in friction welded joint. Additionally, the frictional flow and stirring effect of Al alloy also resulted in the convex on friction surface at steel side stripped into Al alloy, enhancing the appearance of IMCs particles. Therefore, frictional plastic flow was supposed to predominately contribute to the growth of IMCs in friction welding of Al alloy to steel.

A review on friction stir welding: A sustainable way of manufacturing

Abstract Friction stir welding (FSW) process has gained popularity due to its energy efficiency in joining similar or dissimilar materials as compared to traditional way of joining materials and as it involves no use of shielding gas and little harmful emissions due to which it is regarded as ‘green technology’. It’s a solid-state joining process in which plastic deformation takes place to join the similar or dissimilar materials rather than melting. Due to this its applications can be found in the field of industries ranging from aerospace to ship building and rail to electronics. FSW plays a key role in joining many ‘non-weldable’ aluminium alloys such as from 2xxx series alloys (Al-Cu) and 7xxx series alloys (Al-Zn) which is not possible with conventional process leads to softening of weld plates which leads to decrease in the mechanical properties. Hence, the study of various interlayers such as zinc, copper, brass, nickel, tin etc. has become a hot topic for researchers. The joining of dissimilar material is often difficult due to difference in physical properties and composition and hence use of interlayer in FSW helps in effective joining. Insertion of interlayer between the interface of plates to be joined not only enhances the tensile strength of the weld joint but also restricts the excessive formation of hard and brittle intermetallic compounds (IMCs) and leads to controlled formation of fine and uniformly distribution of IMCs and reduces the residual stresses and further increases the joint efficiency. This work contains the review of some important research papers on FSW of similar alloys (Al-Al), dissimilar alloys (Al-Mg), and effects of interlayer on similar alloys (Al/Cu/Al) and dissimilar alloys (Al/Zn/Mg). This paper also throws light on effects of process parameters such as (tool rotation, tool transverse speed, tool materials) on joining of materials by FSW has been discussed along with the suggestions of the researchers.

Ultrasonic effect on thickness variations of intermetallic compound layers in friction stir welding of aluminium/magnesium alloys

• The thickness variation of intermetallic compounds (IMCs) along the Al/Mg boning interface were characterized. • Ultrasonic vibration can reduce the thickness of IMCs on the whole Al/Mg boning interface. • The maximum thickness of IMCs locates at about 1 mm below the top surface of welds on transverse cross-section. • The variation trend of average thickness of IMCs on two horizontal cross-sections were compared and analyzed. The formation of intermetallic compounds (IMCs) in friction stir welding of Al and Mg alloys worsens the strength and toughness of dissimilar joints. Understanding of the morphology and thickness variation of IMCs at different locations inside the weld will lay solid foundation for mitigating the unfavorable effects of IMCs. In this study, friction stir welding tests of Al/Mg alloys with and without exertion of ultrasonic vibration were performed, and the distribution of IMCs at transverse and horizontal cross-sections of welds were observed and characterized at more checking points. The results show that as the depth distance from the top surface of weld gets larger, the thickness of IMCs on transverse cross-section increases first and then decreases, and reaches the maximum value at a depth of about 1 mm. On the horizontal plane at upper part of weld, the thickness of IMCs first increases and then decreases as the distance gets farther from the center of the exit hole, and reaches a stable stage outside of the range covered by the shoulder. The application of ultrasonic vibration can reduce the thickness of IMCs in the whole weld, and make the peak value of IMCs thickness appear at a location nearer the exit hole on horizontal planes at both upper and lower parts of weld.

Intermetallic size and morphology effects on creep rate of Sn-3Ag-0.5Cu solder

The creep behaviour of directionally solidified SAC305 (96.5Sn-3Ag-0.5Cu wt%) alloy has been investigated with integrated particle matrix composite (PMC) crystal plasticity modelling and quantitative experimental characterisation and test. In this manuscript, the mechanistic basis of creep rate dependence is shown to be influenced by plastic strain gradients, and the associated hardening due to geometrically necessary dislocation (GND) density. These gradients are created due to heterogenous deformation at the β-Sn phase and intermetallic compound (IMCs) boundaries. The size and distribution of IMCs is important, as finer and well dispersed IMCs leading to higher creep resistance and lower creep rates, and this agrees with experimental observations. This understanding has enabled the creation of a new microstructurally homogenised model which captures this mechanistic link between the GND hardening, the intermetallic size, and the corresponding creep rate. The homogenised model relates creep rates to the microstructure found within the solder alloy as they evolve in service, when ageing and coarsening kinetics are known.

Performance and emissions of a diesel engine using Al–Fe–Mg–Si pistons contain up to 15.7% volume fractions of Fe-rich intermetallic compounds

Engine performance and emission characteristics were investigated using a single cylinder four-stroke diesel engine with different concentrated intermetallic-based Al–Fe–Mg–Si pistons. Three different alloy combinations (types A, B, and C) of Al–Fe–Mg–Si pistons were developed through the incremental alloying addition of Fe, Mg, Mn, Cu, and Ni. Piston types A, B, and C had Fe-rich intermetallic compounds (IMC), where types B and C had a higher density IMC distribution than type A. The influence of Fe, Mg, Mn, Cu, and Ni alloyed IMC pistons on engine performance and emissions was investigated at various loading conditions. Combustion characteristics such as cylinder pressure and net heat release rate for all piston types were investigated and compared. A similar duration of ignition was seen for all piston types. Frictional loss was reduced by ∼25% in types B and C in comparison to type A. Similarly, mechanical and thermal efficiency were enhanced considerably in types B and C compared to type A. Emission characteristics were also investigated for all piston types. Results showed that NOx was reduced by ∼17.3% with the use of types B and C.

Effect of Laser Beam Oscillation on Laser Welding-Brazing of Ti/Al Dissimilar Metals.

Ti4Al6V and 6061 Al dissimilar metals were butt welded by the laser oscillating welding method. The effects of laser offset, oscillation frequency, and energy distribution on the formation, microstructure, and tensile properties of dissimilar metal joints are discussed in detail. The experimental results show that the Ti6Al4V was micro melted with a laser offset of 1.1 mm, and a large number of intermetallic compounds (IMCs) were formed on the side of the Ti6Al4V. Additionally, there were some porosity defects in the fusion zone (FZ) due to an inappropriate laser oscillation frequency. When the laser offset was increased to 1.2 mm, the IMC distribution was uniform and the thickness was controlled below 2 μm. The porosity defects in the FZ decreased and the tensile strength of the joints increased significantly. The maximum value of tensile strength reached 173 MPa at a laser frequency of 28 Hz.

Boron-containing intermetallic compounds in Mn–Cu–Al/430 stainless steel brazed joints formed under a borate brazing flux

Intermetallic compounds (IMCs) distributed at the interface reduce the bonding strength of Mn–Cu–Al alloy/430 stainless steel (430SS) brazed joints. Here, we investigated the formation mechanism of IMCs to improve the reliability of brazed joints. Mn–Cu–Al high-damping alloy and 430SS were induction-brazed assisted by Cu–34Mn–6Ni–6Sn filler metal and borate brazing flux. Shapeless IMCs were observed to be distributed in chains at the joint interfaces. Moreover, shear cracks propagated along the IMC chains. The IMCs were determined to be (Fe, Cr, Mn)2B; elemental B could only come from the brazing flux according to the materials used for brazing. We propose that IMC formation consists of four stages: (i) substrate dissolution and filler metal diffusion, (ii) B2O3 reduction, (iii) IMC nucleation, and (iv) needle growth and chain distribution of IMC.

Effect of polycrystalline Cu microstructures on IMC growth behavior at Sn/Cu soldering interface

This paper investigated the morphologies of intermetallic compounds (IMCs) forming between pure Sn solders and different polycrystalline copper substrates with microstructures of fiber structure, equiaxed crystal and columnar crystal respectively as well as the effect of Cu microstructures on IMC growth kinetics. The results showed that when multiple IMC grains could be accommodated in a single grain area of substrates, the IMC growth behavior on some grains of polycrystalline substrates was similar to that on single crystalline substrate of same orientation. The difference on polycrystalline Cu substrates was that IMCs with different morphologies appeared alternately. Furthermore, the IMC distribution at soldering interface was stripy on fiber structure and blocky on equiaxed crystal substrates. With increasing of reflow temperature or time, IMCs with different morphologies followed their own growth behavior. In addition, the grain growth rate of IMCs on columnar crystal substrate was higher than that on the other two substrates due to different Cu supply and diffusion abilities.

Effect of beam oscillation on porosity and intermetallics of electron beam welded DP600-steel to Al 5754-alloy

Formation of porosity and intermetallic compounds (IMCs) were studied in electron beam welded (EBW) DP-600 steel to Al-5754 alloy joints at three different weld conditions such as without beam oscillation, with beam oscillation and with varying beam oscillation diameter. X-ray Diffraction (XRD), scanning electron microscopy (SEM), microhardness, three-dimensional X-ray computed tomography (XCT) were used to characterize porosity and IMCs distribution in these weld joints. Beam oscillation with optimum oscillation diameter (1 mm diameter) improved the weld quality by reducing the amount, maximum size and porosity contents in weld zone significantly. For IMCs, average size increased little bit but maximum size, percentage of formation and amount reduced. By increasing oscillation diameter (2 mm diameter) beyond optimum value (1 mm diameter), quality of joints was found to deteriorate with accompanying higher porosity content, average pore size, average IMCs size etc. Raman spectroscopy and gas analyzer were also used to identify and quantify the entrapped gases in the weld joint.

The effect of friction stir processing and post-aging treatment on fatigue behavior of Ca-added flame-resistant magnesium alloy

Friction stir processing (FSP) was applied to the microstructural modification of the extruded flame-resistant magnesium (Mg) alloy, AMX602. The as-received material exhibited microstructure, in which intermetallic compounds (IMCs) were inhomogeneously dispersed in the matrix. FSP broke up some large IMCs and resulted in homogeneous distribution of IMCs and fine grains of the matrix. The micro hardness of the FSPed material was lower than that of the as-received one because the dislocation density and hardening precipitates decreased due to the heat input during FSP. The hardness of the FSPed material increased by the post-aging treatment. However, the fatigue strengths of the FSPed and post-aged specimens were lower than those of the as-received ones. The lower fatigue strengths of the FSPed specimens were attributed to the decrease of hardness by FSP. EBSD analyses revealed that strong texture was developed by FSP. The fatigue cracks of the post-aged specimens initiated at the locations with strong texture, in which basal slip planes had an angle about 45° to the fatigue loading direction. The lower fatigue strengths in the post-aged specimens were attributed to the texture-induced fatigue crack initiation mechanism.

Influence of small addition of antimony (Sb) on thermal behavior, microstructural and tensile properties of Sn-9.0Zn-0.5Al Pb-free solder alloy

Eutectic Sn-Zn alloy is considered as one of the best lead free solder alloys in microelectronic industry. That motivates our group to select different weight percentage of Antimony (Sb) (0.5, 1.0, and 1.5wt%) as an alloying to Sn-9.0Zn-0.5 Al solder alloy. The thermal behavior, microstructure modification as well as tensile properties of the new developed solder alloys were investigated. A slight increment of the melting temperature (∼ 1°C) was recorded using differential scanning calorimetry (DSC) after additions of Sb. For 1.5wt% of Sb, two endothermic peaks at 200.8°C and 201.5°C were observed, which are assigned as hypoeutectic Sn-Zn composition. X-ray diffraction (XRD) measurements confirm the existence of β-Sn phase, α-Zn phase, and Sb-Sn intermetallic compounds (IMCs). Scanning electron microscope (SEM) images indicate that the Sb additives refine the microstructure and form a uniform distribution of IMCs in the matrix of solder. The road-like α-Zn phase, Al6Zn3Sn and SbSn IMCs were clearly appeared in β-Sn matrix, which are responsible of the enhancement in tensile strength. Moreover, α-Zn phases in the Sn-9Zn-0.5Al-1.5Sb alloy were modified as needle-like, broken enormously, depleted, and circle shapes. Generally, The Sb-containing alloys have higher ultimate tensile strength (UTS) and lower elongation than Sb-free solder alloy due to the solid solution and second phase dispersion strengthening effect. The relationship between UTS and temperature follow the Arrhenius law. The average activation energies (Q) were found to be 44.4 ± 1.0kJ/mol, and the average stress exponents (n) were usually around 5.3 ± 0.45, which are close to pipe diffusion controlled creep in β-Sn matrix.