Eutectic Layer Research Articles

Microstructure and properties of Mg/Ti joint welded by resistance spot welding with an aluminum interlayer

Magnesium alloy AZ31B and titanium TA2 were welded by resistance spot welding technology employing an interlayer of aluminum foil and asymmetric electrodes. The microstructure of the joint was observed, with an analysis conducted on the impact of welding current and welding time on the tensile shear load of the joint. During the welding process, the aluminum interlayer melted and blended with the molten magnesium alloy, leading to the formation of a eutectic layer consisting of Mg17Al12 and (Mg) in close proximity to the welding interface. As the increasing of welding current or the extending of welding time, there was an initial increase followed by a slight decrease in the tensile shear load of the AZ31B/TA2 joint. At a welding current of 16 kA, the tensile shear load of the joint achieved the maximum, which was approximately 6.48 kN. The findings suggest that it is effective to use an aluminum foil as an intermediary to regulate the metallurgical reaction at the interface and utilize nonsymmetrical electrodes for thermal compensation in the resistance spot welding between titanium and a magnesium alloy.

New insights into the influencing mechanism of ultrasonic vibration on interface of Al/Mg bimetal composites by compound casting using simulation calculation and experimental verification

In this work, the numerical simulation of acoustic pressure distribution in ultrasonic vibration-assisted compound casting of Al/Mg bimetal composites was conducted. Relevant experimental verification was also performed to understand the influence of ultrasonic vibration treatment (UVT) on the interfacial microstructures and mechanical properties of the Al/Mg bimetal composites. Results revealed that the acoustic pressure distributions in the AZ91D melt were related to the vibration frequencies. The effective cavitation area at the Al/Mg interface reached the maximum percentage of 95.6 %, with the ultrasonic frequency of 20 kHz. The experimental results found that the Al/Mg interface without UVT was composed of Al–Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) layer and eutectic layer. The oxide film and gas gap were existed between the two layers. The Mg2Si particles were gathered at the IMCs layer. The interfacial grains were coarse and their growth was directional. With UVT, the effective cavitation was occurred at the Al/Mg interface. The oxide film was broken, and the gas gap was eliminated. The interfacial microstructures were significantly refined. Due to the accelerated elemental diffusion and solute transfer by UVT, a more homogeneous Al/Mg interface was obtained. The Mg2Si particles were refined and formed at the eutectic layer. The microhardness mismatch of the IMCs layer and eutectic layer was decreased by UVT. The shear strength of the Al/Mg bimetal composites with UVT was enhanced to 62.2 MPa, which increased by 62.8 %, compared with that without UVT.

INVESTIGATION OF SILVER FORGERIES OF ANCIENT COINS: CASE STUDY OF SILVER COINS OF PARTHIA (ORODES II AND PHRAATES VI)

The investigation into the elemental composition and microstructural characteristics of ancient coins gives valuable information to researchers which greatly aid in the detection of counterfeits. This research aim is analysis encompasses an examination of major and trace elements present in the coins of Parthia, to identify forgery techniques utilizing the PIXE technique. The results show the elements Cl, Ca, Fe, Cu, Ag, Au, Pb, Sn, and Zn were identified and according to the ratio Ag/ Cu, can be said that the Parthia period occasionally used forged silver-plated coins. The elemental composition of silver coins of Orodes II and Phraates IV observes these coins are made with plating silver and affixed to the core utilizing a silver-copper eutectic layer, while the core itself consists of copper, and quantities of tin (Sn) were detected which may have been intentionally added for metallurgical, political, or historical reasons.

Effect of Alloying Elements in Steels on the Interfacial Structure and Mechanical Properties of Mg to Steel by Laser-GTAW Hybrid Direct Lap Welding.

Mg alloy AZ31B was directly bonded to SK7 with a low alloy content, DP980 with a high Mn content, 316L with a high Cr and high Ni content by laser-gas tungsten arc welding (GTAW) and hybrid direct lap welding. The results showed that the tensile loads of AZ31B/SK7 and AZ31B/DP980 joints were 283 N/mm and 285 N/mm respectively, while the tensile load of AZ31B/316L joint was only 115 N/mm. The fracture and interface microstructures were observed using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and identified through X-ray diffractometry (XRD). For AZ31B/SK7 and AZ31B/DP980, the interface of the front reaction area and the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase. However, for AZ31B/316L, the interface of the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase, but a multi-layer composite structure consisting of the Mg17Al12 compound layer and eutectic layer was formed in the front reaction area, which led to a deterioration in the joint property. The influencing mechanism of Mn, Cr and Ni elements in steel on the properties and interface structure of the laser-GTAW lap joint between the Mg alloy and the steel was systematically analyzed.

Encapsulated cementite enhances catalytic performance of carbon nanotubes for oxygen reduction reaction

Nonprecious-metal-based materials show great potential to be highly efficient catalysts for oxygen reduction reaction (ORR). There is still room for improvement in the performances of nonprecious-metal-based catalysts for ORR. In this paper, we investigated the catalytic performances of N-doped carbon nanotubes (CNTs) with encapsulated cementite (Fe3C@CNT) for ORR. The encapsulation structure was confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses. The catalytic performances of Fe3C@CNT for ORR were investigated by cyclic voltammetry, linear sweep voltammetry, Tafel analysis, rotating disk electrode, and rotating ring-disk electrode tests. The results showed that both the onset potential and half-wave potential of Fe3C@CNT-catalyzed ORR were 60 mV higher than those of 20 wt% Pt/C catalyst. Fe3C@CNT catalyzed ORR mainly happened through a four-electron pathway. The long-time running stability of the Fe3C@CNT was also superior to that of the 20 wt% Pt/C catalyst. The eutectic layers between the CNTs and cementite enhanced the electron transfer from the inner-layer CNT to the surface-layer N-doped CNT. Calculations revealed that the iron and carbon in the cementite were in positive and negative electronic states, respectively. The encapsulated cementite promoted the formation of equipotential circles on the surface-layer CNT, which greatly enhanced the catalytic performance of the Fe3C@CNT for ORR. N-doped CNTs with encapsulated cementite show great potential to be high-performance catalysts for ORR.

Investigation on indirect laser welding of copper to aluminum

Laser beam welding of aluminum (Al) to copper (Cu) is challenging due to the formation of intermetallic compounds that are brittle and have high resistivities. However, the Cu/Al phase diagram shows a region were solubility of Cu in Al is present and, on the other hand, a region with the formation of a eutectic phase between α-Al and Al2Cu is present as well. Targeting this area turned to be advantageous for solid state welding, as shown for probeless Friction-Stir-Spot-Welding realizing ductile joints between Al and Cu.In this paper an approach based on indirect laser welding of Cu with Al will be presented and discussed. A green laser was used in order to join Cu to Al in lap joint configuration. The laser beam irradiates the Cu surface, whereby the formation of a common melt pool between Cu and Al is avoided. The heat input and the temperature gradient are assumed to support diffusion at the interface between Cu and Al forming a near eutectic layer. Indeed, a melting layer is formed at the interface between Cu and Al supporting joint formation based on a firmly bonding between both materials. The solidified layer presents a copper rich area towards the copper sheet with plate-like structures of Al2Cu, a region with α-Al crystals on the aluminum side and a eutectic layer of lamellar Al2Cu and α-Al in between. The described morphology is very similar to investigations on probeless Friction-Stir-Spot-Welding, whereas a very low pressure is adopted in indirect laser welding and Al-oxide layer seems not to act as a barrier for joint formation.

Synergistic control of microstructures and properties in eutectic high-entropy alloys via directional solidification and strong magnetic field

The AlCoCrFeNi2.1 eutectic high-entropy alloy (Ni2.1 EHEA), as an exemplary representative of the high-entropy alloy family, has garnered significant research attention owing to its exceptional comprehensive properties. In this study, we investigated the influence of various growth velocities on the microstructure, lamellar spacing, and mechanical properties of the Ni2.1 EHEA. We observed that at lower growth velocities, the structure consisted of an alternating face-centered-cubic (FCC) phase and B2 phase lamellae aligned in a single direction, with the lamellae orientation parallel to the direction of the heat flow. The yield strength increased with the growth rate, while the ultimate tensile strength decreased with increasing the growth velocity. Ductility remained relatively consistent, and a double yield phenomenon was observed in the elastic-plastic deformation region. Under conditions of high growth velocities, the microstructure transitioned from a single-directional full lamellar structure to a multi-stage lamellar arrangement. The most favorable comprehensive mechanical properties were achieved at a growth rate of 200 μm/s, resulting in a yield strength of 450 MPa, an ultimate tensile strength of 1092 MPa, and a remarkable ductility of ∼32% in the directionally solidified samples—double that of the arc-melted sample. The evolution law of directional solidification structures under the coupling effect of different magnetic fields and different growth rates was studied. The interaction of the thermoelectric-magnetic force and thermoelectric-magnetic convection and the potential mechanism of microstructure evolution under the effect of magnetic field were deeply analyzed. The results reveal that at a growth rate of 2 μm/s, the spacing between eutectic layers decreases as the magnetic induction intensity increases, leading to the transformation of some regular layers into spherical layers. Similarly, at a growth velocity of 10 μm/s, the eutectic structure exhibited a Columnar-to-equiaxed transition (CET). However, as the growth rate further increases, the limited exposure time to the magnetic field prevented significant structural changes.

A novel W/FeCoCrNi-based in-situ formed high-entropy alloy gradient coating with Laves-FCC dual-phase structure and synergistic friction behavior

Based on the two-way diffusion behavior of FeCoCrNi and W elements and the lattice distortion principle during alloy solidification, a new type of HEA wear-resistant coating with Laves phase and hardness gradient was prepared in this work. Analysis results show that the Laves phase has higher hardness and resistance to deformation, while the FCC phase exhibits higher plastic deformation ability. The tribological properties of the coating material under both room- and high-temperature wear conditions are improved by the synergistic effect of the hard Laves phase and the ductile FCC phase. Moreover, the transition effect of the intermediate eutectic layer alleviates the stress concentration during the friction process, and the oxide film shows a strong wear resistant under the room-temperature wear condition.

Micromechanical study of intragranular stress and strain partitioning in an additively manufactured AlSi10Mg alloy

This study addresses the effect of a cellular-dendritic microstructure on the intragranular deformation behavior of an additively manufactured AlSi10Mg alloy. Experimental investigations have revealed the Al dendritic cells with a characteristic size of several hundred nanometers. The cells are decorated by a thin eutectic layer which consists of an aluminum matrix reinforced by silicon nanoparticles. Based on the experimental data, a set of micromechanical models are constructed and implemented in finite-element calculations. The constitutive behavior of an aluminum phase is described in terms of anisotropic elasticity to take into account the crystal lattice effects. Calculation results are analyzed and discussed with the main focus being placed on the effect of microstructure-resolved stress and strain partitioning between Al and Si phases. The silicon content is shown to impact the range of stress variation at the intragranular scale and the places of stress concentration in the Al phase. The eutectic layer behaves as a metal matrix composite where reinforcing silicon particles restrict deformation of the aluminum matrix.

Fabrication of High-Temperature Solder by Zn Plating Films Containing Al Particles

This study investigated the microstructure and melting point of the Zn–Al composite electroplating film. The cross-sectional microstructure and shear strength of the joints made from the plating films were also evaluated. Zn and Al were confirmed in the plating films from initial microstructure observation. The plating film prepared by a plating bath without cationic surfactant melted near the melting point of Zn and the eutectic point of Zn–Al. When jointed at a joining temperature of 443°C, joining pressure of 5 MPa, and holding time of 5 min, multiple intermetallic compounds, Zn–Al eutectic layers, and unreacted Al particles were observed in the joint layer. From quantitative analysis, the multiple intermetallic compounds were estimated to be Zn–Ni and Zn–Al–Ni intermetallic compounds. The shear strength of the joints increased with increasing joining pressure but was lower than that of Sn–5Sb solder. Fracture after the shear test was observed at the interface between unreacted Al particles and Zn–Al–Ni intermetallic compounds, and inside unreacted Al particles.

Synergistic promotions of K doping on CO2 capture and in situ conversion

AbstractThe integrated CO2 capture and conversion (iCCC) technology has been recognized as a promising strategy for upcycling the emitted CO2 into artificial carbon sequestration but still demands highly efficient dual functional materials (DFMs). We develop an efficient iCCC process of the integrated lithium‐looping (LiL) and reverse water gas shift reaction through deeply understanding K doping in the novel Kx‐Li4SiO4@Niy DFMs. The appropriate K doping enables the fast diffusion of CO2 and H2 into the bulk DFMs through forming LiKCO3 surface eutectic layer as well as strongly interacts with catalyst Ni to generate new medium basic sites for synergistic promotions of CO2 capture and in situ conversion. More importantly, after the pelletization, the LP‐K0.2‐Li4SiO4@Ni10 DFM (20–40 mesh) avoids the agglomeration and achieves an excellent and stable iCCC cycle performance, with CO2 capture capacity of 3.8 mmol/g, CO2 conversion efficiency of 90%, and CO selectivity close to 100% at 550°C in one fixed‐bed column.

Joining mechanism, microstructure, and mechanical properties of AZ31/6061 joint prepared by pouring fusion welding process assisted with Zn-xSn brazing filler

In this study, AZ31/6061 dissimilar metal joints were manufactured using pouring fusion welding assisted with Zn-xSn brazing filler, and the process, microstructure and mechanical properties of Mg/Al joint were investigated. During welding, the addition of molten Zn-xSn brazing filler completely isolates the direct contact of Mg/Al, preventing the formation of Mg-Al intermetallic compounds. As the Sn content changes, the microstructure of the joints also changes. When the Sn content is 25 wt.%, the microstructure of the AZ31 side is dominated by Mg-Al-Zn ternary eutectic structure, Al6Mg11Zn11, (β-Zn + MgZn2), Al-Zn-Sn (SS), Sn (SS) and Mg2Sn. And the microstructure of the 6061 side is dominated by Al-Zn-Sn (SS), β-Zn, Al-Zn-Sn (SS), and Sn (SS). The width of the Mg-Al-Zn ternary eutectic structure layer decreases with the increase of Sn content. In addition, high Sn content and high heat input promote the formation of Mg2Sn, and large amounts of Mg2Sn are generated with Zn-40Sn interlayer. The average microhardness of the joint gradually decreases with the increase of Sn content. However, the shear strength of the joint first increases and then decreases, and the shear strength of the joint with the Zn-25Sn interlayer is the highest, which is 50.60 MPa. Fracture mode is cleavage fracture.

Comparison of Solidification Microstructure Evolution of Al-10Si and Recycled Aluminium Beverage Can Strips Made in a Strip Caster

A strip caster was used to cast two types of aluminium alloys: an almost eutectic Al-Si alloy (Al 10 Si) with contaminants of 0.6 Fe, 0.2 Pb, and 1.4 Sn, which exhibits a polyphase microstructure upon solidification, and recycled aluminium beverage cans made from Al 0.8 Mn alloy containing 0.4 Si, 0.5 Fe, and 0.1 Mg, which has a monophase microstructure upon solidification. The molten materials were poured at 650 oC (Al 10 Si) and 670 oC (Al 0.8 Mn, 0.4 Si, 0.5 Fe, 0.1 Mg) on a cooling slope specially designed to obtain a semisolid material. This semisolid material was then dragged between rolls at a rate of 0.2 m/s to obtain high-quality metal strips. There was less eutectic modification with larger Al-α grains in the middle region of the sheet between the fine eutectic layers, indicating a lower cooling rate. However, during the recycling of aluminium beverage cans, large grains were formed with a columnar structure at the interface of the rolls, and semisolid melts with cracks were formed between the columnar grain boundaries owing to the compression of the rolls. The middle of these grains contained smaller equiaxial grains that were subjected to dragging. The as-cast specimens were submitted to homogenisation heat treatment at 560 oC for a period of 10 h and cooled to room temperature before being cold rolled (Temper H18) and recrystallised (Temper O) to examine the effect of these treatments on the tensile mechanical properties. During cold rolling (Temper H-18), grain alignment occurred with a yield stress, maximum stress, and elongation of 209.5 MPa, 210.1 MPa, and 2.8%, respectively. The strength decreased (yield stress of 58 MPa and maximum stress of 120.2 MPa) under recrystallisation conditions (Temper O), but the ductility increased (8.9%). This is in contrast to the Al-Si (Al 10Si) strip, which exhibited a yield stress, maximum stress, and elongation of 103.3 MPa, 128.7 MPa, and 1.9%, respectively. The A1 10Si strips also fractured during cold rolling, indicating high material fragility.

A novel stress-relaxing approach based on forming Fe–Ni invar effect interlayer for joining C/C composites

Taking advantage of the invar effect of Fe–Ni alloy at low temperatures, a novel stress-relaxing approach based on forming Fe–Ni invar interlayer was proposed for joining carbon fiber reinforced carbon (C/C) composites in this paper. Mixed Fe + Ni62Ti38 (at %) powders were used as the filler materials. Microstructure, mechanical property, and formation mechanism of the bonded joints were investigated. The results indicate that, based on the eutectic reaction of (Fe,Ni)–C at the C/C/interlayer interface and the in-situ reaction of Ti–C in the interlayer, a (Fe,Ni)–C eutectic reaction layer was formed at the C/C side interface and the Fe–Ni invar effect interlayer reinforced by TiC particles was obtained. Owing to the low thermal expansion coefficient and good plasticity of the Fe–Ni alloy matrix at low temperatures, the high residual thermal stress of the joint was effectively reduced and the shear strength of the joint was improved. With the increase of Ni content in the Fe–Ni alloy matrix of the interlayer, the shear strength of the joint decreases gradually. When the composition of the Fe–Ni matrix was designed to be Fe–36Ni, i.e., the invar alloy with the lowest thermal expansion coefficient at 100 °C, the average shear strength of the bonded joint reached the highest value of 36 MPa. The fracture of the joint occurred in the (Fe,Ni)–C eutectic reaction layer close to the C/C composite.

P‐10.4: A Non Photolithographic Black Light Shield Film for Ultra‐low Reflectivity Micro‐LED Display

Reflectivity, one of the most key specifications for display, is pursued to be extreme low to match the name of ultimate display for micro-LEDs. Conventionally, black light shield film is fabricated by photolithographic process before or after the micro- LED chips being mass transferred to the driver substrate to meet this requirement. In this study, we report a novel black light shield film material by a simple and effective graphical process to achieve ultra-low reflectivity with little influence on the light output of LED chips to dispense with complicated lithography process, which can fill the gap between the LED chips and the eutectic layer at the bottom of the LED chips, and expose the top of the micro-LED chips simultaneously. The black light shield film was directly adhered to the micro-LED substrate by heating, vacuum and press. Whole surface ashing process was then carried out to remove the excess black light shield film on the surface of the micro-LED substrate. By optimizing the thickness of removed black film, the surface of the micro-LED chips could be exposed while other places were still covered with black light shield film. A full-color Micro-LED display with 114 PPI resolution and size of 1.98-inch was successfully fabricated and showed superb performance with 1.16% reflectivity.

Microstructure evolution, mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

In this paper, the effect of the Si content on microstructure evolution, mechanical properties, and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically. The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer (MRL), whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites, while the hypereutectic Al-Si/AZ91D composites were opposite. The MRL included eutectic layer (E layer), intermetallic compound layer (IMC layer) and transition region layer (T layer). In the IMC layer, the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg2Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites. Besides, increasing Si content, the thickness proportion of the T layer increased, forming an inconsistent preferred orientation of the MRL. The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content, and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa, which was 73.4% higher than the Al-6Si/AZ91D composite. The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content. The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg2Si particle reinforcement, the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

Interfacial characteristics, mechanical properties and fracture behaviour of Al/Mg bimetallic composites by compound casting with different morphologies of Al insert

ABSTRACT The effect of surface morphologies of Al insert, including smooth surface (SS), straight knurling (SK) and hatching knurling (HK) on interfacial microstructure, mechanical properties and fracture behaviour of Al/Mg bimetallic composites by a novel compound casting was studied in this work. The thicknesses of the interface layers of the SK-s and HK-s bimetallic composites, respectively, increased by 11.5% and 4.8% than that of the SS’s composite. The interfacial phase compositions were similar for all the bimetallic composites, mainly consisting of eutectic layer (EU) and intermetallic compound layer (IMC). Therein, the proportion of the EU layer in the entire interface layer for the SK’s and HK’s bimetallic composites was larger than that of the SS’s sample. The EU layer had a lower hardness than the IMC layer. The shear strengths of the SK’s and HK’s bimetallic composites increased by 34.2% and 50.2%, respectively, compared to that of the SS’s bimetallic composite.

Microstructure, mechanical properties and biocompatibility of laser metal deposited Ti–23Nb coatings on a NiTi substrate

To simultaneously obtain superior superelasticity and biological properties, single- and multi-layer Ti–23Nb coatings were deposited on a cold-rolled NiTi substrate using laser metal deposition (LMD). The microstructure of the single-layer coating consisted of a cellular structure with a grid size of ∼300 μm in the eutectic layer, strip structures and prior β-(Ti, Nb) phases surrounded by the Ti2Ni(Nb) phase in the Ni diffusion zone. In contrast, the microstructure of the multi-layer coating consisted of α′, α′′, and prior β phases, which arise from the partition of Nb. Compared with the NiTi substrate, the Ni ion release concentration of the single-layer coating is reduced by 45% with similar nano-mechanical behavior, i.e. a nanohardness, H, of ∼4.0 GPa, a reduced Young's modulus, Er, of ∼65 GPa, an elastic strain to failure, H/Er, of ∼0.06, a yield stress, H3/Er2, of ∼0.016 GPa, and a superelastic strain recovery, ηsr, of ∼0.3. The reduction of Ni ion concentration for multi-layer coating after 35 days is even better at up to 62%, but at the cost of a degradation in the mechanical properties. The LMD coatings have a high dislocation density, and their creep is controlled by dislocation movement.

Understanding the microstructural evolution and strengthening mechanism of Al/Mg bimetallic interface via the introduction of Y

The heavy rare earth element Y was introduced into the Al/Mg bimetallic interface prepared by a compound casting process in the form of Mg–Y master alloy, in order to improve the interfacial microstructure and bonding strength of the Al/Mg bimetal. The results showed that the original eutectic structures and the primary Mg17Al12 (γ) dendrites at the Al/Mg interface were significantly refined. Al–Y phase (Al2Y) and Al–Mn–Y phase (Al6Mn6Y) formed in the Al/Mg bimetallic interface. Due to the fine grain strengthening and the precipitation strengthening brought by the RE precipitates in the eutectic layer and primary γ layer of the Al/Mg bimetallic interface, the bonding strength of the Al/Mg bimetallic interface with the Y addition was enhanced up to 50.98 MPa with an increase of 39.63%. Compared with previous studies, it was found that the lower Y addition (about 0.2 wt%) can achieve the strengthening effect similar to that of the light rare earth elements with high addition (about 0.7–1.0 wt%). In addition, the fracture location of the Al/Mg bimetallic interface changed from the intermetallic compounds zone to the primary γ layer of the eutectic zone after the Y addition.

Friction stir solid–liquid spot welding of Cu to Al assisted by Zn interlayer

The relatively low joint performance restrains the application of Cu/Al dissimilar metals welding structure. In order to obtain a high-quality Cu/Al joint, the friction stir solid–liquid spot welding was proposed. At the same time, the Zn interlayer was used and three probes with different lengths were adopted. The assisted Zn interlayer improved the joint quality by regulating the interfacial microstructure. The IMCs layers at the bonding interface of Cu/Al were composed of Al4.2Cu3.2Zn0.7 layer and Al2Cu layer or αAl + Al2Cu eutectic layer. The long probe produced more heat, larger pressure and stronger material flow at the lap interface, while the thickness of IMCs layer reached the maximum under the 1.3 mm-length probe because of the most residual liquid phase. Under the 1.3 mm-length probe, the maximum tensile shear load of the Zn-added joint was 6.64 kN, and this value was 0.51 kN bigger than that of conventional joint. The joints all fractured at the lap interface, but the fracture modes in micro-level were diversified. The hole and crack defects at the bonding interface influenced the micro-fracture mode fracture.