Cu-Al Intermetallic Compounds Research Articles

Unraveling elastochemical effects in microstructural evolution of Al–Cu–Ni system through DFT-informed multi-phase field simulations

Through the multi-phase field method, this research explores microstructure evolution within the Al–Cu–Ni system comprising Al-rich FCC, Al2Cu, and Al3Ni intermetallic compounds (IMCs). Notably, the Al3Ni exhibits substantial growth due to its higher free energy magnitude, while the Al2Cu phase diminishes within the FCC matrix. Additionally, this study investigates the impact of heterogeneous elastic effects on these microstructural changes. Density functional theory calculations were employed to determine temperature-dependent elastic tensor at a simulation temperature of 723 K. Initially both cases, simulations with elastic constants at 0 K and 723 K, start with identical grain areas. But by 21.45 ms, deviations notably intensify to 18.18% for single grains, underlining the importance of temperature-calibrated elastic tensor in the phase evolution driven by elastochemical effects.

Study on strengthening and toughening mechanisms of Cu/Al composites dominated by interface layer

Cu/Al composites have the excellent properties of both Cu and Al, and have the properties of light weight and high conductivity, so they have been widely concerned. In this paper, 5-mm-thick Cu/Al composites prepared by the cast-rolling process are used as experimental materials. To reveal the strengthening and toughening mechanisms of the Cu/Al composites, the interfacial structure, micro-morphology, stress-strain condition, and GND distribution of Cu/Al composites before and after deformation were characterized utilizing TEM, TKD, and EBSD. The results show that the submicron intermetallic compounds Al2Cu and Al4Cu9 are formed from the casting-rolling Cu/Al composites. After 15% tensile deformation, many gaps occurred in the interface layer, but at the gaps, there was no crack spreading to the Cu and Al layers. Meanwhile, the deformation in different directions occurs in the Cu grains near the interface, forming a dislocation wall, and the entanglement of the dislocation occurs in the Cu layer near the interface, which contributes to the improvement of tensile strength. The Al layer near the interface layer produces kink bands, which helps to improve the ductility of the composites. Besides, due to the action of the hard intermetallic compound layer, with the increase in tensile deformation, a large number of GND are gradually accumulated in the Cu and Al layers near the interface, resulting in remote back stress, which makes the softer Cu and Al layers obtain higher strength. At the same time, the back stress caused by GND will induce strain hardening, which helps to maintain ductility, so that Cu/Al composites have higher plastic deformation ability while improving mechanical properties.

Influence of Cu Addition on the Wear Behavior of a Eutectic Al–12.6Si Alloy Developed by the Spray Forming Method

In the present study, the influence of the addition of copper (Cu) on the wear behavior of a Al-12.6Si eutectic alloy developed using the spray forming (SF) method was discussed, and the results were compared with those of as-cast (AC) alloys. The microstructural features of the alloys were examined using both optical and the scanning electron microscopy, and the chemical composition and phase identification were achieved by X-ray diffraction (XRD) analysis. The results revealed that the microstructure of binary the SF alloy consisted of fine primary and eutectic Si phases, evenly distributed in the equiaxed α-Al matrix, whereas the Cu-based SF ternary alloy consisted of uniformly distributed fine eutectic Si particulates and spherical-shaped θ-Al2Cu precipitates, uniformly distributed in α-Al matrix. In contrast, the AC ternary (Al-12.6Si-2Cu) alloy consisted of unevenly dispersed eutectic Si needles and the coarse intermetallic compound θ-Al2Cu in the α-Al matrix. The addition of Cu enhanced the micro hardness of the SF ternary alloy by 8, 34, and 41% compared to that of the SF binary, AC ternary, and binary alloys, respectively. The wear test was conducted using a pin-on-disc wear testing machine at different loads (10–40 N) and sliding velocities (1–3 ms−1). The wear tests revealed that SF alloys exhibited an improved wear behavior in the entire applied load and sliding velocity range in comparison to that of the AC alloys. At a load of 40 N and a sliding velocity of 1 ms−1, the wear rate of the SF2 alloy is 62, 47, and 23% lower than that of the AC1, AC2, and SF1 alloys, respectively. Similarly, at a sliding velocity of 3 ms−1, the wear rate of the SF2 alloy is 52%, 42%, and 21% lower than that of the AC1, AC2, and SF1 alloys, respectively. The low wear rate in the SF2 alloy was due to the microstructural modification during spray forming, the precipitation of fine Al2Cu intermetallic compounds, and increased solid solubility. The SF alloys show an increased transition from oxidative to abrasive wear, while the AC alloys demonstrate wear mechanisms that change from oxidative to abrasive, including delamination, with an increase in sliding velocity and load.

Effect of Dispersing In Situ Al-Cu Intermetallic Compounds on Joint Strength in Friction Stir Welding of AA3003-H18 Sheets

In this study, friction stir welding (FSW) was employed to join AA3003-H18 sheets by incorporating in situ Al-Cu intermetallic compounds within the stir zone. The FSW process was carried out under three distinct conditions: (I) without applying powder, (II) by introducing Cu powder, and (III) by incorporating Cu-Al mixed powder (50 vol.% Cu, 50 vol.% Al). The powder was embedded into the gap between two sheets. Subsequently, two-pass FSW, involving both forward and backward movements, was conducted with a rotational speed of 1200 rpm and traverse speed of 100 mm/min across all three experimental conditions. In the second and third conditions, the formation of in situ intermetallic compounds occurred through a solid-state reaction between Cu particles and Al within the stir zone. Examination of the stir zone through optical and electron microscopic studies revealed that the utilization of Cu-Al mixed powder resulted in finer and more uniformly distributed Cu clusters and Al-Cu intermetallics than samples welded with Cu powder alone. Notably, the stir zone of samples incorporating Cu-Al mixed powder exhibited finely dispersed, completely gray Al-Cu intermetallic particles, whereas those with only Cu powder displayed predominantly coarse core-shell particles in the microstructure. The introduction of Cu-Al mixed powder during FSW resulted in a stir zone with an average hardness of 74 HB, showing a 14% increase compared to the cases where Cu powder alone was added (65 HB). Tensile tests, conducted in both transverse and longitudinal directions on the FSWed samples, did not exhibit a consistent trend across the three mentioned conditions. Transverse tensile strength consistently ranged between 107 and 110 MPa, with joint efficiency varying from 52% to 54%. However, the longitudinal tensile strength of the joint with added Cu-Al mixed powder (158 MPa) surpassed those welded with Cu powder alone (134 MPa).

Thermal Misfit and Diffusion Induced Stresses of Cu-Al Intermetallics in Microelectronics Wire Bonding

The thermosonic bonding technique is a widely used method for Cu wire interconnections. However, issues arise due to volumetric changes in intermetallic compounds (IMCs) formed at the Cu-Al bonding interface, leading to voids in the Cu-Al IMC layer. This problem is exacerbated after annealing, such as in high-temperature Storage (HTS). In this study, a statistical modelling approach was employed to quantitatively analyse stress, studying the evolution and characteristics of the interfacial microstructure in the thermosonic Cu wire-Al bond pad system. Microstructural analysis focused on Cu-Al IMC crystallography and compositional classification. A stress model was proposed, considering both thermal misfit and diffusion-induced stresses. Results showed that interfacial stress generally increased with higher bonding temperatures. The influence of forming gas supply was relatively minor, with oxide layers minimally impeding Cu-Al interdiffusion during Cu-Al IMC formation. This stress modelling technique hold potential as a valuable failure analysis tool for implementing Cu wire in various industries.

Mechanism of toughness enhancement of brittle fracture by intermittent η-intermetallic in Al/Cu joint made by FSW

It is well documented that the mechanical failure mechanism of various compounds of aluminum 1050 and commercial pure copper (Al/Cu) involves a combination of brittle and ductile fracture processes. Brittle fracture occurs through the intermetallic compounds (IMCs), while ductile fracture occurs through the base materials, either in the stir zone or the heat-affected zone. In this study, a clean and uniform Al/Cu interface was created using the Friction Stir Welding (FSW) technique, which allowed the investigation of the mechanism of pure brittle fracture in Al–Cu IMCs, using a notched tensile specimen. Fracture surfaces were analyzed in detail using scanning electron microscopy (SEM) and microstructural characterization techniques. SEM analysis of the Al/Cu interface revealed the presence of continuous Al2Cu, intermittent AlCu (η), and continuous Al4Cu9. Fractography results showed that the brittle fracture was multilayered and multi-faceted, with an intergranular fracture observed between the Al2Cu and Al4Cu9 IMCs. This crack was stopped by the intermittent AlCu IMC, resulting in transgranular fracture through AlCu. Cracks in the AlCu phase were deflected toward the Al/Al2Cu interface, resulting in delamination of the Al/Al2Cu interface. It was found that this multilayer fracture, induced by the intermittent AlCu between Al2Cu/Al4Cu9, provided the high tensile strength of the compound (173 MPa) compared to the values reported in the literature. A comparison of the Al/Cu joints with Al/steel joints also confirmed the contribution of this fracture deflection to the improved joint strength.

Fabrication of Al matrix composite reinforced with Fe-Cu particles using friction stir processing

Friction stir processing (FSP), as an advanced technique, was employed to fabricate in situ aluminum composites with the aim to elucidate the correlation between microstructure and mechanical properties of the obtained composites. The novelty of the work is to utilize simultaneous incorporation of Fe and Cu powders into the friction stir zone in order to fabricate in situ aluminum composites. To achieve the goal, the loading content of Cu and Fe powders and the process pass number (1 pass to 5 passes) were altered. While the total loading content of Fe and Cu powders was kept constant, the weight percentages of these reinforcements were varied (25%, 50%, and 75%). Microstructural characteristics were examined using scanning electron microscopy and optical microscopy. Five passes FSP resulted in smaller grain sizes of the Al matrix, smaller and less agglomeration of the reinforcements as well as homogeneous dispersion of the reinforcement features and thus, enhancement of the mechanical properties of the composites. X-ray analysis and energy dispersive spectroscopy confirmed in situ formation of Fe-Al and Al-Cu intermetallic compounds in the composites. The tensile testing outcomes proposed the 50wt% Fe-50wt% Cu/Al composite fabricated in 5 passes as the optimum formulation achieved in this research. This can be attributed to the smaller grain size of the matrix in the friction stirred zone and more homogeneous dispersion of the reinforcements in the matrix. Furthermore, this strengthening was affected from the presence of more amounts of well dispersed intermetallic compounds in situ formed during 5 passes. The average tensile strength (207 MPa) and hardness (73 Vickers) of the composite were approximately 175% and 160% greater than that of the unreinforced aluminum (75 MPa, 28 Vickers), respectively. Increasing the process pass number from 3 to 5 passes not only had strengthening and hardening effects but also improved the composite elongation at break.

Purification of the Al2Cu intermetallic compound via zone melting crystallization technique

The widespread interest in intermetallic compounds has driven the development of their structures and properties, as well as their applications as alternative structural and potentially functional materials. As more and more intermetallic compounds with complex compositions enter the application market, their performance improvement and sustainable recycling face many challenges, where the influence of impurities plays a crucial role. Here, we proposed the direct purification of intermetallic compounds by fractional crystallization and verified for the first time the feasibility and effectiveness of zone melting for the purification of intermetallic Al2Cu. After ten passes of zone melting, results showed no separation of Al and Cu, the major components of Al2Cu. Further analyses demonstrated the homogeneity and remelting stability of Al2Cu before and after zone melting. In addition, the total impurity concentrations at the front and the end of cast Al2Cu bars decreased with increasing number of passes, respectively. After ten passes of zone melting, Al2Cu bar with an initial purity of 3N exhibited higher refining efficiency than those with an initial purity of 4N. Among all impurities, the distribution coefficients of Fe, Si, Zn, and Ti were obviously less than unity (k < 1). Whereas the impurities Ca, Mg and Mn showed behaviors of distribution coefficients less than and/or close to unity.

The microstructure and mechanical properties of aluminum/steel welded joint by FSLW

Friction stir lap welding experiments between 6061 aluminum alloy and DP590 dual-phase steel plates were carried out. The effects of welding parameters and the addition of Cu foil interlayers with 0–0.3 mm thickness on the microstructures and mechanical properties of the lap joints were investigated. The shear strength of the joint reached the maximum value of 5337 N and showed a mixed ductile-brittle fracture mode when the welding speed, the rotating speed, and the thickness of the Cu foil intermediate layer were set to 80 mm/min, 900 rpm, and 0.1 mm, respectively. The plastic Al2Cu and AlCu intermetallic compounds formed through Al and Cu reaction at the aluminium alloy/steel interface play a beneficial role in the Cu-added joint strength.

Investigation of CuAl IMCs Corrosion in Chloride Environment and its Prevention Strategy

Abstract In most current wire-bonding applications, electrical interconnection is accomplished by fine Cu wires bonded to Al bonding pads microfabricated on an IC chip and external contact pins of the PCB board. Corrosion-related failure defects between the Cu wire and Al bond pad have been an ongoing un-trackable reliability issue plaguing the IC packaging industry for the past ten years, despite approaching ppb levels. Most prior studies hypothesized that intermetallic compounds (IMCs) like Cu9Al4, and CuAl2 were responsible for the observed acute wire-bond lift-off corrosion defects. Further studies sought to quantify the rates of corrosion of these IMCs and explore the effects of mitigation efforts of adding Pd, relevant to Pd-coated Cu wire-bonding. However, utilizing a novel real-time corrosion screening approach, we previously established that peripheral bimetallic contact between Cu ball-bonds and Al bond pads also plays a substantial role in the aggressive Al pad corrosion, induced by chloride ion penetration, which often leads to device failure. In this work, we further explored the role of IMCs corrosion in wire-bond lift-off failure utilizing fundamental electrochemical studies to quantify rates of galvanic-induced corrosion of IMCs within the broader context of an interconnected stack of Al bond pad, Cu-Al IMCs and Cu bonding wire. We also explored the use of a corrosion inhibitor to suppress the galvanic corrosion currents of Al bond pad, and Al-rich IMCs when electrically connected to Cu wire or Cu-rich IMCs.

Macro- and Microstructure of In Situ Composites Prepared by Friction Stir Processing of AA5056 Admixed with Copper Powders.

This paper is devoted to using multi-pass friction stir processing (FSP) for admixing 1.5 to 30 vol.% copper powders into an AA5056 matrix for the in situ fabrication of a composite alloy reinforced by Al-Cu intermetallic compounds (IMC). Macrostructurally inhomogeneous stir zones have been obtained after the first FSP passes, the homogeneity of which was improved with the following FSP passes. As a result of stirring the plasticized AA5056, the initial copper particle agglomerates were compacted into large copper particles, which were then simultaneously saturated by aluminum. Microstructural investigations showed that various phases such as α-Al(Cu), α-Cu(Al) solid solutions, Cu3Al and CuAl IMCs, as well as both S and S'-Al2CuMg precipitates have been detected in the AA5056/Cu stir zone, depending upon the concentration of copper and the number of FSP passes. The number of IMCs increased with the number of FSP passes, enhancing microhardness by 50-55%. The effect of multipass FSP on tensile strength, yield stress and strain-to-fracture was analyzed.

Microstructure characteristics and mechanical properties of Cu/Al laminated metal composites fabricated by electropulsing assisted ultrasonic additive manufacturing

In this paper, electropulsing (EP) technique was employed to enhance the capability of ultrasonic additive manufacturing (UAM) of metals. The microstructure and mechanical properties of Cu/Al laminated metal composites (LMCs) fabricated by EP-UAM and preheating (PH) assisted UAM were comparatively investigated. Results show that by introducing EP into UAM, the synergistic effect of ultrasonic shear and EP is produced, which promotes the plastic flow of Al near the Cu/Al interface, offsetting the negative influence of no-preheating. Compared to the PH-UAM, EP-UAM induces atomic diffusion and formation of a tiny of Cu-Al intermetallic compounds more effectively, which is beneficial to the interfacial bonding strength. The Cu/Al LMCs fabricated by EP-UAM exhibited an obviously higher tensile strength and total elongation than those by PH-UAM. Such improvements in mechanical properties are mainly ascribed to (ⅰ) the higher strength retained for Cu and Al layers, (ⅱ) the cooperative deformation of Cu/Al and (ⅲ) back stress strengthening due to the formation of Cu atoms Guinier-Preston (GP) zones within Al matrix.

Joining multiple-layer Al-Cu thin foils by a novel Resistance Rolling Welding method for battery application

A novel resistance welding method called Resistance Rolling Welding (RRW), in which a roller upper electrode and a flat lower electrode were adopted, was developed to realize a long-distance, large-area and multiple-layer Al-Cu welding with a flat weld surface. In this study, three Al layers and a single Cu layer were joined by RRW via various mechanisms. The Al layers adjacent to the Cu layer were joined due to Al2Cu intermetallic compound generation via Al melting and Cu diffusion, while those far away from the Cu layer were joined owing to the dynamic recrystallisation caused by the large deformation and high welding temperature. With increasing the welding current from 6 kA to 10 kA, the peak load of joints in the coach-peel test first increased up to the maximum, then decreased. The electrical resistance of the entire joints and the corresponding interlamination resistance for each interface showed the similar tendency: first decreased then increased with the increasing currents. A sound dissimilar joint with the highest coach-peel load (185.25 N) and the relatively lower electrical resistance was thus obtained at 9 kA via RRW.

Tensile properties optimization of Al/electroplating-Cu composites fabricated by accumulative roll bonding (ARB)

A novel method combing electroplating and ARB was used to manufacture multilayer composites in this research. Pure Cu was electroplated on the Al-1060 and stacked with the Al-1060 sheets alternately; as a result, the multilayer metals were made into composites by ARB. It is indicated that both grains and AlCu intermetallic compounds significantly refined, together with well-bonded interfaces after ARB. Note that the tensile properties improved significantly. By applying 6 cycles of ARB, both the yield stress (YS) and ultimate tensile stress (UTS) were increased by more than 100 MPa and a negligible adverse influence on the elongation was caused. Therefore, it is very promising to apply this strategy of combining electroplating and ARB to produce composites with superior properties.

The interplay of precipitation of ordered compounds and interfacial segregation in Al‐Cu‐Hf‐Si alloys for high-temperature strength

Achieving high yield strength (250-270 MPa) at elevated temperatures (250 °C and above) for precipitation strengthened aluminium-copper (Al-Cu) alloys still remains a challenge for the alloy designers. This paper presents a systematic progression of the microstructure evolution in a binary Al-0.3Hf, ternary Al-0.3Hf-0.3Si and quaternary Al-2Cu-0.3Hf-0.3Si (in at%) alloys. A quantitative understanding of the role that Hf and Si plays in promoting ordered precipitates and the metastable Al-Cu intermetallic compounds θ"/θ' has been attempted. The initial microstructure is guided by the initial precipitation of primary phases, triggering the formation of Hf-rich dendrites and finally, the Si/Cu segregation at boundaries. Ageing of binary Al-Hf alloy results in precipitation of L12 ordered phase via discontinuous (cellular) process. Si, however, promotes a continuous precipitation process, resulting in the formation of coherent and spherical L12 ordered phase in the matrix. The role of these ordered precipitates in influencing the precipitation of θ"/θ' compounds in quaternary copper containing alloy was explored in detail, including their coarsening and mechanical properties at elevated temperatures. The compact morphology developed in the alloy results in yield strength of 445 ± 8 MPa at room temperature (25 °C). The yield strength evolves through the interaction of L12and θ"/θ' ordered phases with the α-Al matrix. The coarsening of θ' phase was slowed down due to Hf segregation at a semi-coherent interface and led to a thermally stable microstructure that resulted in yield strength of 256 ± 8 MPa at 250 °C.

Evaluation of the macro/microstructure of Al/Cu/Sn/Ni multi-layered composite produced by accumulative-roll-bonding (ARB) and post-heat treatment

In this study, an Al/Cu/Sn/Ni multi-layer composite (MLC) was produced by a two-step process (i.e., accumulative roll bonding and subsequent heat treatment) for up to six cycles. The effect of the two-step process on the macro/microstructure of the Al/Cu/Sn/Ni MLC was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, and x-ray diffraction pattern. The results show that the Ni and Sn layers in the sandwich cycle and the Cu layer in the 1st cycle fractured in the Al matrix. Finally, during the 6th cycle of the two-step process, a uniform distribution of Ni, Cu, and Sn reinforcement layers was achieved in the Al matrix. Moreover, during the 3rd cycle, an Al3Ni2 intermetallic compound was formed at the interface of the Al/Ni layer. Also, during the 6th cycle, in addition to the formation of the Al3Ni2, an AlCu intermetallic compound was formed at the interface of the Al/Cu layer. The recrystallization phenomenon in the Al matrix occurred during the sandwich, 3rd, and 6th cycles, too. In addition, during the various cycles, grain growth also occurred in the Al matrix so that the size of some grains in the Al matrix during the 3rd and 6th cycles reached about 2 and 1 µm, respectively.

Revealing growth mechanisms of faceted Al2Cu intermetallic compounds via high-speed Synchrotron X-ray tomography

This study used high-speed synchrotron X-ray tomography to image the growth of Al2Cu intermetallic compounds in 4D (3D plus time) during solidification of Al-45wt%Cu alloy. Two categories of growth patterns (basic units and dendrites) are identified. Basic units are elongated rods whose cross-section are L, U or hollow-rectangular shapes. The transition from L pattern to U and finally to hollow-rectangular shaped morphology is observed. Faceted dendritic patterns include equiaxed prism and columnar dendrites. Self-repeated layer-by-layer stacking of the basic units (such as L shaped particles) is proposed as a governing mechanism for the growth of Al2Cu faceted dendrites. The growth orientation and morphologies of these patterns are strongly influenced by solidification conditions (temperature gradients, cooling rates and external magnetic fields). Another finding is that when rotating Al-45wt%Cu during upwards directional solidification, under a transverse magnetic field of 0.5T, highly refined and well aligned Al2Cu intermetallic compounds are obtained, much finer than those without the imposition of the magnetic field. This is attributed to a rotational stirring flow that modulates and regulates the temperature and solute distribution. The developed experimental findings provide a physical understanding of the formation of faceted intermetallic compounds during solidification.

Effect of Annealing Temperature on the Interfacial Microstructure and Bonding Strength of Cu/Al Clad Sheets with a Stainless Steel Interlayer.

To explore the influence of annealing temperatures on the interfacial structure and peeling strength of Cu/Al clad sheets with a 304 stainless steel foil interlayer, an intermediate annealing treatment was performed at temperatures of 450 °C, 550 °C, and 600 °C, separately. The experimental results indicate that the interfacial atomic diffusion is significantly enhanced by increasing the intermediate annealing temperature. The average peeling strength of the clad sheets annealed at 550 °C can reach 34.3 N/mm and the crack propagation is along the steel/Cu interface, Cu-Al intermetallic compounds layer, and Al matrix. However, after high-temperature annealing treatment (600 °C), the liquid phase is formed at the bonding interface and the clear Cu/steel/Al interface is replaced by the chaotic composite interfaces. The clad sheet broke completely in the unduly thick intermetallic compounds layer, resulting in a sharp decrease in the interfacial bonding strength.

Synthesis of Al2Cu intermetallic compound by mechanical alloying

The alloy composition of Al-33.33 at% Cu (Al-54.15 wt% Cu) was selected for the present research. The effect of the milling duration on the synthesis of Al2Cu intermetallic compound was analyzed using several analytical techniques like XRD, SEM, EDX, HRTEM, and DSC/TGA. Nanostructured Al2Cu was successfully synthesized by mechanical alloying (MA) of Al-33.33 at% Cu powder for more than 15 h followed by annealing of the milled powder in Ar atmosphere at 1000 °C for 2 h. Residual Al and Cu powder that has not been transformed to Al2Cu were found in the milled powder even after 20 h of milling. Rietveld analysis was done for a better understanding of the phases evolved during MA and the annealing of the milled powders. The synthesis of the nanostructured intermetallic compound Al2Cu by MA followed by annealing of the milled powders was confirmed by analysis of the powders using various techniques.

Interfacial Behavior and Shear Strength of Al-25Si-4Cu-1Mg Joints by Transient Liquid Phase Bonding with Cu as Interlayer

Spray-formed hypereutectic Al-Si-Cu-Mg alloy is the candidate for automotive and aerospace industries due to its superior wear resistance, lower thermal expansion coefficient and density, and higher thermal conductivity. This paper aims to investigate the bonding properties of hypereutectic Al-25Si-4Cu-1Mg alloys using the transient liquid phase (TLP) method with Cu as an interlayer. To obtain the suitable bonding parameters, the interfacial microstructure and shear strength of Al-25Si-4Cu-1Mg joints were investigated with the effect of different bonding temperatures and holding times. The results showed that TLP bonding between Al-Si-Mg-Cu alloy was mainly realized by large amounts of Al2Cu intermetallic compounds (IMCs), primary Si and α-Al phases. With the brazing temperature increasing, the width of the brazing seam gradually increased, and the voids began to be produced. With the holding time increasing, θ-Al2Cu phases approached into the base metal and Si particles in the brazing seam were obviously coarsened. With the formation of θ-Al2Cu phases into the base metal, more Si particles were segregated at the interface between brazing seam and base metal, and the shear test confirmed that it was the weakest bonding location. Finally, the effect of bonding parameters on the joint strength indicated that the joint brazed at 540 °C for 7.5 min presented the best shear performance with the shear strength reaching 75 MPa because the size of Si particles in the brazing seam was closest to the size of Si particles in base metal under this parameter.