IMC Formation Research Articles

Influence of Temperature on Creep Resistance, Structural and Electrical Characteristics of S9Z1 Eutectic Alloys

In the present study, the structural and creep resistance properties of S9Z1 alloys with Cu-addition in concentrations (0.1 and 0.3% Wt.) have been investigated using x-ray diffractions (XRD) and Creep testing machine respectively. The three samples were prepared from high purity 99.99% by melting technique in the Pyrex tubs with CaCl<sub>2</sub> to invaded the oxidation. The obtained samples were rolled drawn (cold rolling) into two groups. The first group was as wires for the creep resistance testing. The second group was as small sheets for structural investigations. Patterns of XRD showed that the S9Z1 alloy was primarily composed of two phases; a body centered tetragonal β-Sn matrix phase, and a secondary phase of hexagonal Zn. while with addition Cu (0.1 and 0.3% Wt.) to S9Z1 Alloys the results showed new peaks in the ternary compositions, such as Cu<sub>6</sub>Sn<sub>5</sub>, Cu<sub>5</sub>Zn<sub>8</sub>, phases respectively. The average of particle size (D) of β-Sn matrix was decreased with increasing Cu -adding, whereas the dislocation density (δ) increased with increasing addition. Creep properties of S9Z1, S9Z2 and 3 Alloys were examined at different temperatures (25, 40 and 80°C) under two constant loads (σ= 18.7 and 24.94 MPa). The creep behaviors of ternary alloys were higher than the S9Z1 alloys with all different temperatures under two constant loads. Also, the S9Z3 alloy with all different temperatures and two loads exhibited greatest creep resistance, due to the refinement structure and formation of new IMCs. Values of stress exponent (n) were found to be in the range of 1 to 10.55, for all S9Z2 and 3 alloys respectively. Values of activation energy (Q) of alloys were found to be in the range of 36.48 to 37.49 kJ/mol, for σ = 18.7 Mpa and 27 to 34.8 kJ/mol for σ = 24.94 Mpa for the S9Z1 alloys with Cu addition respectively. At room temperature (25°C), the electrical conductivity of the samples was calculated, and its values increased with Cu additions.

Advancements in joining Al-Zn-TiC-Mg composites using friction stir welding process: Influence of traverse speed

In this article, dissimilar magnesium and aluminum alloys were welded with a Zn interlayer and TiC nanoparticles by friction stir welding. Optimal joining conditions were achieved by a combination of three traverse speeds (30, 45, and 60 mm/min) and constant rotational speeds (1050 rpm). The best microstructure evolution and mechanical properties were achieved for specimens joined at rotational and traverse speeds of 1050 rpm and 45 mm/min, respectively. The grain size decreases as the traverse speed increases from 30 to 45 mm/min due to a reduction in heat input, an improvement in reinforcing distribution, and high intermixing of materials, then increases from 45 to 60 mm/min due to inadequate heat input for recrystallization process. It was shown that the TiC particles play a prominent role in the microstructure modification and enhance mechanical properties of weld samples while the Zn foil interlayer plays a vital in avoiding the formation of Al-Mg IMC phases. The obtained result under optimal welding parameters indicates that MgZn2, Mg-Al-Zn compounds, Mg and Al solid solution, were the main detected common phases in the stir zone instead of the brittle and hard Al-Mg IMCs formation. The average hardness values of 232 Hv were achieved, while the strength of the weld specimen experiences the 189 MPa value. In addition, a combination of brittle and ductile modes was observed based on the fracture surface of the weld sample after the tensile test.

Microstructure, hardness, electrical, and thermal conductivity of SZCN solder reinforced with TiO2 and ZrO2 nanoparticles fabricated by powder metallurgy method

The microstructure and characterization of Sn–Zn–Cu–Ni (SZCN) solder alloy reinforced with TiO2 and ZrO2 nanoparticles (NPs) synthesized by powder metallurgy were investigated. Sn, Zn, Cu and Ni metallic powders were mixed mechanical by 10:1 ball to powder ratio with 300 rpm speed for 2 h. Then 0.5 wt% from nano ZrO2 or TiO2 was mixed by the same parameters with the mixed metal powder. The morphologies and microstructures development during the fabrication process was investigated by X-ray diffractometer (XRD), optical microscope (OM), and scanning electron microscope (SEM) with energy dispersive X-ray spectrometry (EDX). The results reveal an improved distribution of TiO2 or ZrO2 NPs in the SZCN matrix solder, which resulted in an improvement in its density. The analyses of microstructural demonstrated that the addition of TiO2 or ZrO2 NPs to SZCN solder results in the grain refinement of the β-Sn phase, besides the formation of Ni3Sn IMC with small size and uniform distribution. The microhardness was enhanced as a result of the addition of TiO2 or ZrO2 NPs. The experimental results showed that the SZCN-ZrO2 composite solder had the greatest hardness and stress exponent values due to its effectiveness in suppressing the growth of β-Sn grains and the pile-up of dislocations. Both the electrical and thermal conductivities were improved by incorporating TiO2 NPs compared to other solders.

Influence of bonding time during diffusion bonding of Ti–6Al–4V to AISI 321 stainless steel on metallurgical and mechanical properties

Diffusion bonding was employed to join AISI 321 stainless steel to Ti–6Al–4V titanium alloy via Cu–Zn foil as the interlayer. The influence of bonding time (30, 45 and 60 min) at 900 °C temperature with the pressure of 2 MPa on the microstructural and mechanical behaviors of the joints is evaluated. The optical and scanning electron microscopes were utilized to examine the microstructural characteristics of the Ti–6Al–4V/Cu–Zn/AISI 321 stainless steel joints. Results displayed that three distinct reaction layers have been created as a result of the brazing process at all joints. It was also found that a longer bonding time led to the widening/expanding of the reaction/diffusion layers. The attained data also showed that bonding time affected the formation of brittle IMCs including CuTi2, CuTi, FeTi, Fe22Zn78 and TiZn3 phases within the interface as a result of the increased diffusivity of reaction elements and subsequently resulted in the reduction of the shear strength of the diffusion bonded joints from 281 MPa for bond made at 30 min to about 174 MPa for bond made at 60 min. Decreasing the shear strength by rising the bonding time can be a sign of expanding the level of interfacial reaction at the joints.

Influence of tool positions variation on axial force, torque sensitivity, mechanical and microstructure properties of Al/Cu dissimilar FSW

ABSTRACT Study on tool offset must be necessary to minimise IMCs formation and mechanical properties enhancement. Tool offset has a significant variations in the instantaneous force and torque are measures for the welding process. Increasing in the offset means more % of Al. This means softer IMCs formation and so increasing in offset distance decrease on load in the spindle/Z-axis and X-axis torque. A precise critical offset towards Al plate could result in a defect-free joint and superior mechanical performance. 1.5 mm offset gives smooth variations in the peaks, indicating a uniform distribution of the intermetallic compound, smooth weld surface and defect-free weld leads to better mechanical properties. In comparison to the Al base metal, the weld sample had more tensile and yield strength of 95% and 100%, respectively in case of optimised offset of 1.5 mm. 1.5 mm offset give maximum compressive strength (97.5% of the Al BM), maximum tensile properties and micro-hardness (176.2HV) due to fine grain with Al 44 μm and Cu 42 μm. As the grain size decreases so it helps to increase tensile properties and the strength of the joint depends on the offset distance and formation of the suitable amount of the intermetallics.

A comparative study of the activation energy and shielding properties of some binary and ternary echo-friendly alloys reinforced by Bi substitutes Zn particles for radiation protection

The thermal and mechanical stability besides environmentally friendly of some low-melting binary systems dopant with third element such as Bi started to gain much attention. This study provides the synthesized, effects of rapid solidification processing (RSP) and Bi doping on the microstructural, mechanical performance and gamma radiation shielding of various lead-free binary and ternary alloys have compositions Sn-(50-x)Zn-xBi (where x = 0, 10, 20, 30 and 40 wt.%) using high cooling rate. Microstructure modifications, elastic and plastic behavior were investigated. As well as the gamma-ray shielding performance of all as-prepared melt-spun process alloys was examined experimentally using FH 40G dose rate measuring unit. Phy-X/PSD software was used to compute the μ m values across a large energy range of 0.015 MeV–15 MeV. To clearly understand the gamma radiation shielding capability of the melt-spun process alloys, different shielding parameters includes linear attenuation coefficients, LAC, mass attenuation coefficient, MAC, mean free path, MFP, half value layer (HVL) and tenth value layer (TVL) were calculated and compared to other commonly shielding materials. X-ray diffraction (XRD) analysis confirms the presence of different phases such as β-Sn, Bi, Zn as well as two IMCs Sn0.95Bi0.05 and Sn0.85Zn0.15. The morphology features of the samples using scanning electron microscopy (SEM) revealed that Bi particles dopant the matrix led to refine the microstructures as well as forming a uniform and homogeneous distribution of IMCs. It is also, reported that the increase of Bi dopant led to enhancing the Bi segregation in the matrix in addition to decreasing the crystallite size which reinforces the mechanical strength and radiation shielding properties. The elastic modulus and Vickers microhardness increase with increasing Bi additions to about 35% and 27%, respectively. The results showed that correlation between activation energy and shielding properties of as-prepared alloys. The mass and linear attenuation coefficient for all prepared samples increases as Bi increases from 10 to 40 wt.%. On the other hand, low activation energies indicate easier formation and growth of IMCs. The results also show that the Sn-10Zn-40Bi alloy has the highest mechanical and shielding attenuation properties. It may be attributed to promoting the brittleness of Bi, refinement of crystallite size, extended the solid solubility and microstructure features accompanying Bi content using rapid cooling. As a result, Sn-10Zn-40Bi alloy may be recommended as a preferable alloy for radiation shielding performance to be used for medical, industrial and nuclear waste storage fields. In the current work, an attempt has been made not only to summarize the various investigations made so far on visualizing the feasibility of alloys as radiation shielding material; but also, to provide a comparative study for further consideration to be used in other fields.

Mechanical and Microstructural Characteristics of Rotary Friction Welded SS316L and Pure Copper with Added MWCNT Nano Additives

This study explores the novel design of geometric rubbing profiles on rotary friction welding for enhanced mechanical clamping in joining dissimilar alloys such as copper and stainless steel 316L. The clamping behavior of rubbing profiles could hold the yielding of the weld joint to a maximum level. An innovative approach to effective mixing of the weldment zone could be achieved through the definition of rubbing profiles. The effective dispersion of dissimilar metallic phases could be governed by the geometrical profile in achieving the intermetallic SS-Cu phase. Variations were made in welding parameters like tool rotational speed, upset pressure, upset time, friction pressure, and friction time to find the appropriate process for the four different rubbing profiles, namely helical fluke, plus, cylindrical, and flat to achieve a reduction in micro and macro-structural defects with strong weld nugget. Results show that helical fluke rubbing profiles were seen to have explicit values like ultimate tensile strength of 217 MPa (upset pressure), elongation of 9.8 % (upset pressure), and average hardness of 125 HV (friction pressure) at the weld nugget. Microstructural characteristics prove that the formation of IMCs through grain size reduction such as cementite increases the Vickers hardness of the weldment.

Outstanding ductility of dissimilar laser Al/steel spot joint using a high entropy alloy interlayer

Laser spot welding (LSW) technology was used for the joining of low carbon steel to AA5052 Al alloy using a FeCoNiCrMn equimolar high entropy alloys (HEAs) interlayer for the first time. The addition of the HEA interlayer promoted the formation of a Fe-rich Fe-Al IMC with less brittleness and hardness. It resulted in an increase of the joint fracture load from 963 N to 1473 N and a dramatic improvement of the displacement increased from 0.66 mm to 3.32 mm. Another reason for the outstanding ductility of the dissimilar laser joint was the formation of a conical fusion zone in the joint, which realized the dual coupling of metallurgical bonding and mechanical interlocking at the interface.

Friction stir alloying of AZ61 and mild steel with Cu-CNT additive

Dissimilar joining between lightweight magnesium (Mg) alloys and steel is essential to produce lighter vehicles, improve vehicles’ fuel efficiency, and reduce carbon emissions. However, the joining of Mg to steel is impractical due to the immiscible properties between these metals. In this experiment, friction stir alloying (FSA) is proposed to solve this problem. The additive, consisting of different wt% of carbon nanotubes (CNT) in Cu powder was first added into the gap between the workpieces and then friction stir welding (FSW) was performed at varied traverse speed and constant rotational speed. After the joining, microstructure characteristics and mechanical properties of Cu-CNT reinforced Mg/steel joints were investigated. Transmission electron microscopy (TEM) analysis of the Mg/steel joint revealed the formation of IMC at the interface of the joint. Further analysis by X-ray diffraction (XRD) showed a dominant presence of Mg2Cu IMC which indicated the interdiffusion of Cu into Mg element to establish intermetallic bonding. The presence of CNT inside the Mg matrix was also confirmed by TEM which contributed to the strengthening effect of the joint. Tensile and microhardness results revealed a notable enhancement of joint mechanical properties when Cu-CNT additive was added as compared to specimens with only Cu additive, and specimens without additive. The enhanced tensile strength and microhardness of the Cu-CNT reinforced Mg/steel joint was attributed to the dispersion of CNT inside the Mg matrix, which induced multiple dislocations in the surface region, therefore improving the mechanical properties of the joint.

Effects of Sb and/or Sn concentrations on the SbSn formation in a ternary melt-spun Pb–Sb–Sn alloy

The Pb–Sb–Sn alloy still considered a mandatory choice in the production of the metallic grids in lead-acid batteries. This work aims to study the effects of the commutative concentration of Sb and Sn on the formation of SbSn IMC in ternary melt-spun Pb–Sb–Sn alloy, as well as the effects of initiated on its structural, mechanical and electrical properties. X-ray diffractions (XRD), Dynamic resonance technique, Vickers hardness tester, and High Precision Micro-ohmmeter were used to investigate the melt-spun Pb–Sb–Sn alloys. The results showed that a balanced Sb–Sn content in the melt-spun Pb80–Sb10–Sn10 alloy results in a high concentration of refined SbSn and small particle sizes for α-Pb and SbSn (44.37 and 20.13 nm respectively), low lattice distortion (4.56 × 10−4), low cell volume (120.993 (Å)3), and the highest density (9.232 g/cm3) compared to that of the other melt-spun alloys. Mechanical improvements in terms of room-temperature dynamic Young's modulus (20.8 GPa), bulk modulus (42.3 GPa), shear modulus (7.2 GPa), and Vickers micro-hardness (115.706 MPa) have been revealed, which are strongly related to structural changes. The refined and high concentration of SbSn is responsible for its improved electrical conduction and electrical stability at elevated temperatures (its electrical performance). The aforementioned characteristics suggest that melt-spun alloy is more reliable for use in harsh environments, such as under the hood of a vehicle.

Microstructure evolution and joining strength of diamond brazed on Ti-6Al-4V substrates using Ti-free eutectic Ag-Cu filler alloy

In this study, strong bonding of vacuum brazed synthetic diamond and Ti-6Al-4V substrates joints was achieved using a Ti-free eutectic AgCu filler alloy. It was found that the brazing temperature remarkably influenced the interfacial microstructures, and hence affected the bonding strength of brazed diamond joints. Thermodynamic calculation and TEM microstructural characterization revealed that the rapid adsorption and dissolution of Ti in molten filler alloy is responsible for the preferential precipitation of TiCu and/or Ti2Cu IMCs on the brazed diamond surface and the excessive formation of TiCu IMCs, which largely impaired the bonding strength of brazed Ti-6Al-4V/diamond joints. An evolution model exploring the microstructure and mechanical properties of the brazed joints on Ti-6Al-4V substrates was proposed, by taking the behavior of Ti adsorption into account. The underlying mechanism to gain a reliable bonding between Ti-6Al-4V substrate and diamond in this work is therefore of essential implications for the understanding of microstructure and bonding strength of other hard-to-wet materials on Ti-based substrates.

Remote laser welding of Zn coated IF steel and 1050 aluminium alloy: processing, microstructure and mechanical properties

The integrity of steel-aluminium dissimilar alloy joints is dependent on the intermetallic phases (IMCs) and the extent of the bonding area. The excessive growth of brittle AlxFex IMCs within the weld pool and interfaces is disadvantageous due to the initiation and propagation of hot and cold cracking during the solidification. The purpose of this work was to assess the development of Remote Laser Welded (RLW) joints of Zn coated interstitial free (IF) steel to 1050 aluminium alloy, which can be used in cooling circuits and electrical connectors in automotive applications. Welding experiments with variable RLW parameters (power, welding speed and focal offset) were performed to study the formation of IMCs and impact of joint integrity. Results showed that while in conduction mode (at power densities of 0.13–0.18 MW/cm2) three IMCs were identified through SEM/EDX and EBSD: η – Al5Fe2, κ – AlFe3 and θ – Al13Fe4 which possessed nano-hardness indentation values of approximately 12, 5 and 5 GPa, respectively; they formed in a non-continuous interfacial layer, the weld pool composition remained homogenous, and cracking was minimal. On the contrary, in keyhole mode (at power densities of 0.16–0.40 MW/cm2) welded samples produced a continuous and thick IMC layer, continuous and/or excessive cracking and an inhomogeneous weld pool composition due to the excessive mixing of steel and aluminium, of up to 10 wt.% of Al in the weld pool. The nominal lap shear strength for the sample produced in conduction mode was of 77%, with respect to the weakest joint material (Al). This work found a close link between the welding mode and weld pool chemistry which significantly determined the IMCs distribution and thickness, extent of cracking within the weld pool and mechanical properties.

Effect of Kaolin Geopolymer Ceramics Addition on the Microstructure and Shear Strength of Sn-3.0Ag-0.5Cu Solder Joints during Multiple Reflow.

Solder interconnection in three-dimensional (3D) electronic packaging is required to undergo multiple reflow cycles of the soldering process. This paper elucidates the effects of multiple reflow cycles on the solder joints of Sn-3.0Ag-0.5Cu (SAC305) lead (Pb)-free solder with the addition of 1.0 wt.% kaolin geopolymer ceramics (KGC). The samples were fabricated using powder metallurgy with the hybrid microwave sintering method. Apart from using conventional cross-sectioned microstructure imaging, advanced synchrotron real-time in situ imaging was used to observe primary IMC formation in SAC305-KGC solder joints subjected to multiple reflow soldering. The addition of KGC particles in SAC305 suppressed the Cu6Sn5 IMC’s growth as primary and interfacial layers, improving the shear strength after multiple reflow soldering. The growth rate constant for the interfacial Cu6Sn5 IMC was also calculated in this study. The average growth rate of the primary Cu6Sn5 IMCs decreased from 49 µm/s in SAC305 to 38 µm/s with the addition of KGC particles. As a result, the average solidified length in the SAC305-KGC is shorter than SAC305 for multiple reflow soldering. It was also observed that with KGC additions, the growth direction of the primary Cu6Sn5 IMC in SAC305 changed from one growth to two growth directions. The observed results can be attributed to the presence of KGC particles both at grains of interfacial Cu6Sn5 IMCs and at the surface of primary Cu6Sn5 IMC.

Tribological Behavior of Electrical Connector Sn/Ni/Cu Coating with Intermetallic Compound Layers Under Reciprocating Motion

Electroplating is one of the most common methods for applying electronic connector coatings. This research investigated the tribological behavior of electroplated multilayer coatings of Sn, Ni, and Cu with and without intermetallic compound layers (IMC), which are intermediate compounds formed between two metals under reciprocating sliding. It is found that heat treatment promotes both Sn/Ni IMC and Sn/Cu IMC growth. Based on the test results, the tribological performance of all heat‐treated samples is enhanced due to the high hardness of the IMC. The existence of the Ni layer slows the formation of IMC between the Sn and Cu coatings, but it is not producing a significant improvement from the perspective of tribological performance.

Influence of laser-Sn powder coupling on microstructure and mechanical properties of fusion welded AZ31B-alloy to DP590-steel

Microstructure and mechanical properties were studied in fusion welded AZ31B-alloy to DP590-steel at different weld conditions such as with varying laser power, and Sn powder added to lap joint with prefabricated width-settled concave groove. Temperature field and flow field for laser welding including chemical potential of each element are also calculated. The results suggested that Al atom tends to diffuse toward Fe side which contributes to form a FeAl compound reaction layer at interface. Meanwhile, Al accelerates the diffusion of Sn and Fe as a catalyst. The shear force of joint climbs at first, then declines, and the maximum value reaches 1711 N when laser power is 1 kW, which is improved by 38% compared with that of 0.9 kW. The improved joint properties are dominated by metallurgical regulation of Sn power, which benefits from the accelerated flow of molten pool and increased temperature leading to the phase composition transformation from α-Mg + Mg2Sn + FeAl to α-Mg + Mg2Sn + FeSn + Fe3Sn + FeSn2 + FeAl in direct laser irradiation region. However, under the condition of excessive laser power, overreaction occurs at side boundary interface, which leads to the formation of thick IMC and the production of hot crack defect, thus the joint performance decreases.

The Influence of Indium, In on Microstructure Evolution During Isothermal Aging of Sn-0.7Cu

This paper reports influence of isothermal aging on bulk solder and the microstructure evolution of commercial Sn-0.7Cu (Sn-0.7Cu-0.05Ni+Ge) Pb-free solder alloy with addition of bismuth (Bi) and indium (In). Sn-0.7Cu, Sn-0.7Cu-1.0Bi, Sn-0.7Cu-1.0Bi-1.0In, Sn-0.7Cu-1.0Bi-4.0In, Sn-0.7Cu-1.0Bi-7.0 In solder alloys were prepared via casting process. The solder alloys were aged isothermally at 180°C for 500 hours and microstructure was compared with that of as-cast solder. Microstructure of bulk solder and melting temperatures were analysed via scanning electron microscopy, SEM and differential scanning calorimetry, DSC. The addition of In up to 7 wt% reduced the melting temperature from 231.1 to 218.5°C, and crystallisation temperature from 205.8 to 194.7°C with decreasing degree of undercooling which indicates that the In-added solder alloy had faster nucleation rate. Microstructure evaluation showed that as the amount of indium added increased to 7.0 wt%, the ß-Sn grains became smaller suggesting a refinement effect with In addition. Indium addition also encouraged the formation of Sn-In and Bi-In IMC which increased as the amount of In increased. These IMCs could potentially act as blocking mechanism for deformation leading to higher strength.

Development of a customised model of integrated marketing communications for the economic well-being of the enterprise

In modern marketing theory, marketing communications have adopted a more extended interpretation called customisation. This is the subject of further consid-eration of integrated marketing communications as a systematic approach to do-ing business, which allows making the most of all available business tools today. The purpose of the research was to solve the problems of integrated marketing communications related to the organisation of planning and management, ensur-ing the priority of consumer opinion, creation of individualised goods and services. Customisation is based on completing consumer goods with individual elements, component modules or additional exclusive accessories ordered by customers, whose demands are growing and changing. Customisation is understood not only as ensuring that a product or service meets the needs of a specific consumer, but also as designing them together with a future buyer. The article presents a custom-ised model of integrated marketing communications, which can be used by entre-preneurial structures of the restaurant business in the process of forming a com-plex of marketing communications to ensure the savings of their financial and or-ganisational resources, which lead the economic well-being of the enterprise. Based on the analysis, a formula for a customised model of integrated marketing com-munications was derived, which is based on the dynamics of the stages of the formation of IMC. It was concluded that the authors' model of integrated market-ing communications can be used to ensure the financial savings and economic well-being of enterprise.

Laser lap welding of TC4 titanium alloy to 6082 aluminum alloy using a CoNiCuNb0.5 V1.5 high entropy alloy filler

To avoid the formation of brittle Ti-Al intermetallics, a new welding procedure for Ti-Al alloy joints was proposed. The feasibility of CoNiCuNb0.5V1.5 high-entropy alloy filler metal for laser lap welding of TC4 titanium alloy to 6082 aluminum alloy is investigated in this paper. By adjusting the welding parameters, a small amount of base material on the titanium side was melted. The high entropy of mixing and kinetic sluggish diffusion effects of high-entropy alloy (HEA) are used to facilitate the formation of solid solution structure, obstruct the mixing of titanium atoms and aluminum atoms and thus inhibit the formation of Ti-Al IMCs. The weld seam without Ti-Al IMCs was obtained. At the high-entropy alloy-Al alloy interface, the joint fractured with a maximum tensile strength of 190 MPa.

Performing a comparative study of mechanical properties of Al-Cu composite reinforced with or without bimetallic SiC micro-particle

Butt weld between Al6063-Cu is produced with or without reinforcing SiC (25 µm) to analyze its effect on IMC formation. Al plate is kept on advancing side throughout the process. As a result its observed that on with reinforcement workpiece is less prone to defects when compared with the one without reinforcement and parameters like tool tilt, tool speed, tool offset serves as the critical parameter as a slight change in one leads to significant change in quality of joint produced. It is observed that the best joint is produced with reinforcement taking tool tilt as 1° at 1500 rpm and tool offset of 0.5 mm towards Cu side results in tensile strength of 81.7 MPa and without reinforcement the best joint is obtained at a tool tilt of 2°, tool speed as 900 rpm at 0.3 mm tool offset provided on Cu side resulting in tensile strength of 79.3 MPa keeping a constant feed rate of 7 mm/min.

Nature of CoCrFeMnNi/Fe and CoCrFeMnNi/Al Solid/Solid Interface

To shed light into the application potential of high-entropy alloys as “interlayer” materials for Al-steel solid-state joining, we investigated the nature of the CoCrFeMnNi/Fe and CoCrFeMnNi/Al solid/solid interfaces, focusing on the bonding behavior and phase components. Good metallurgical bonding without the formation of hard and brittle IMC can be achieved for CoCrFeMnNi/Fe solid/solid interface. In contrast to the formation of Al5Fe2 phase at the Fe/Al interface, Al13Fe4-type IMC, in which the Fe site is co-occupied equally by Co, Cr, Fe, Mn and Ni, dominates the CoCrFeMnNi/Al interface. Although the formation of IMC at the CoCrFeMnNi/Al interface is not avoidable, the thickness and hardness of the Al13(CoCrFeMnNi)4 phase formed at the CoCrFeMnNi/Al interface are significantly lower than the Al5Fe2 phase formed at the Fe/Al interface. The activation energies for the interdiffusion of Fe/Al and CoCrFeMnNi/Al static diffusion couple are 341.6 kJ/mol and 329.5 kJ/mol, respectively. Despite this similarity, under identical static annealing condition, the interdiffusion coefficient of the CoCrFeMnNi/Al diffusion couple is significantly lower than that of the Fe/Al diffusion couple. This is thus mainly a result of the reduced atomic mobility/diffusivity caused by the compositional complexity in CoCrFeMnNi high-entropy alloy.