Brazing Seam Research Articles

Microstructure and Mechanical Properties of AZ31B/LY12 Joints Using Zn/Ag–Cu–Zn/Zn Multi-Interlayers via Ultrasound-Assisted Transient Liquid Phase Bonding

The use of a Zn/Ag–Cu–Zn/Zn multi-interlayer was observed to avoid the formation of Mg–Al binary intermetallic compounds (IMCs), which cause embrittlement and low strength of bonding when dissimilar metals such as Mg/Al are joined using ultrasound-assisted transient liquid phase bonding (U-TLP). The change in the microstructure and mechanical properties of the AZ31B/LY12 joints at 410, 440, and 460 °C with prolonging ultrasonic treatment (UST) time was investigated. The results showed that the diffusion of Ag and Cu was faster into the brazing seam on the LY12 side than that on the AZ31B side with increasing UST and temperature. The IMCs on both sides of the joints were transformed with the diffusion of Ag and Cu. The transformation made the fracture path shift from the AZ31B side (410, 440 °C) to the LY12 side (460 °C), and the maximum shear strength of the joints from 43.3 (410 °C) to 65.7 (440 °C) to 84.7 MPa (460 °C). The IMCs on the surface of the fracture path corresponding to the joints with optimal mechanical properties changed from Mg7Zn3+MgZn2+α-Mg (410 °C) to MgZnCu+Mg7Zn3 (440 °C) to Al2Cu (460 °C).

Releasing the residual stress of Cf/SiC-GH3536 joint by designing an Ag-Cu-Ti + Sc2(WO4)3 composite filler metal

• The work is the first one to introduce Sc 2 (WO 4 ) 3 into brazing process. • The Sc 2 (WO 4 ) 3 maintains its negative thermal expansion effect in Ag-Cu-Ti system. • The residual stress releasing mechanism is revealed by finite element analysis method. • The shear strength improves 2.6 times by introducing Sc 2 (WO 4 ) 3 reinforcing phase. Due to native character of thermal expansion coefficient (CTE) mismatch between C f /SiC and GH3536, achieving high strength joint was a huge challenge for C f /SiC-GH3536 joints. Herein, a composite filler metal of Ag-Cu-Ti + Sc 2 (WO 4 ) 3 was developed to join C f /SiC and GH3536. This work introduced Sc 2 (WO 4 ) 3 to Ag-Cu-Ti system as a negative thermal expansion (NTE) reinforcing phase to release joint residual stress. Sc 2 (WO 4 ) 3 was evenly distributed in the brazing seam and reacted with Ti to form Ti 3 O 5 reaction layer. The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc 2 (WO 4 ) 3 reinforcing phase, and the mises stress was decreased from 447 to 401 MPa. The maximum shear strength of the C f /SiC-GH3536 joint brazed with Ag-Cu-Ti + 6 vol% Sc 2 (WO 4 ) 3 filler alloys was 64 MPa, which was about 2.6 times higher than that of Ag-Cu-Ti alloys. The results of this study provide a promising strategy for the introduction of new Sc 2 (WO 4 ) 3 reinforcing phase in Ag-Cu-Ti system, and improve the reliability and feasibility of composite brazing alloy in brazing filed.

High-temperature stability of microstructure and mechanical properties of eutectic-reinforced high-entropy ceramic joint

(HfTaZrNbTi)C5 high-entropy ceramic (HEC) brazed joint was obtained with TiNi-Nb alloy and the brazing seam was primarily filled by TiNi + Nb eutectic microstructure. The highest shear strength of the joint obtained under the condition of 1220 °C/10 min reached 167 MPa and 137 MPa at room temperature and 800 °C, respectively. Moreover, the high-temperature stability of the brazed joint was investigated by air oxidation testing at 800 °C. Compared to the HEC, the TiNi + Nb eutectic microstructure in the brazing seam exhibited superior oxidation resistance. After oxidation for four hours, the joint shear strength still maintained 100 MPa, while it was reduced to 22 MPa after oxidation for eight hours due to the dramatic damage of the HEC. The results showed that the brazed HEC joint possessed high shear strength at an elevated temperature of 800 °C for four hours although the high-temperature endurance of the joint was weak.

Reliable joining Al5(TiZrHfNb)95 multicomponent alloy and Nb using Ti–Ni filler metal

The reliable joining of Al5(TiZrHfNb)95 multicomponent alloy and Nb was achieved by the reaction of Ti–Ni filler and base materials. The relation of the microstructure evolution and brazing temperature was analyzed to reveal the brazing mechanism. The joint property was evaluated by the shear strength. The results showed that the liquid brazing filler reacted with Nb substrate to form a TiZrHfNb layer adjacent to the Nb, and the brazing seam was composed of TiZrHfNb matrix, (Ti,Zr,Hf)2Ni and (Hf,Zr,Ti)2Ni phases. Increasing the brazing temperature promoted the Al5(TiZrHfNb)95 to dissolve into the brazing filler, and the (Ti,Zr,Hf)2Ni and (Hf,Zr,Ti)2Ni phases volume enlarged. The (Ti,Zr,Hf)2Ni and (Hf,Zr,Ti)2Ni phases were beneficial to the property of the brazing seam. But high volume of (Ti,Zr,Hf)2Ni and (Hf,Zr,Ti)2Ni facilitated the propagation of cracks in the brazing seam, seriously weakening the joint shear strength. When the Al5(TiZrHfNb)95 and Nb were brazed at 1150 °C for 20 min, the maximum shear strength achieved at room temperature was 338 MPa, and the crack was located in the brazing seam.

Blackening Mechanism and Mechanical Properties Variation of Zirconia Ceramic Induced by Active Metal Brazing

Blackening of zirconia (ZrO2) ceramics often occurs in active metal brazing, however, its discoloration mechanism and induced variation in mechanical properties remain unclear. Herein, ZrO2 ceramic and Ti are successfully brazed by Ag–Cu–Pd filler in vacuum along with the blackening phenomenon. In the brazed joints, the reaction layers of TiO2 + Ti3(Cu, Pd)O are formed adjacent to ZrO2, indicating that partial oxygen in ZrO2 is taken by active Ti in the liquid filler that dissolved from the Ti substrate. Furthermore, the height of the blackened ZrO2 ceramic near the brazing seam is in line with the amount of Ti content added to the filler, which infers that bulk‐sized black ZrO2 can be efficiently obtained by the interfacial reaction between Ti and ZrO2. Additionally, the black ZrO2 is having abundant Zr3+ defects and more tetragonal phase content than the original ZrO2. The formation of Zr3+ defects results in the blackening of ZrO2, while the phase transformation leads to reduced hardness, improved impact toughness, and enhanced wear resistance of black ZrO2. Thus, this blackening phenomenon of ZrO2 ceramics provides a new way to tune the mechanical properties of ZrO2.

Low residual stress C/C composite-titanium alloy joints brazed by foam interlayer

Metallic foam was introduced as an interlayer to improve the performance of the brazed C/C composite-titanium alloy joint, and the interfacial microstructure and residual stress of the brazed joint were investigated. Compared with the brazed joint without foam, introducing foam interlayer could achieve the uniform bonding interface, and Ag-based solid solution (Ag(s,s)) became more dispersed and smaller in the center of the brazing seam. The thickness of reaction layer close to C/C composite side was less than 1 μm. Some Cu-based solid solution (Cu(s,s)) was detected, indicating that Cu foam still existed after brazing. The residual stress and its distribution calculated by finite element method (FEM), and the residual stress of the brazed joint decreased from 293 MPa to 228 MPa. The introduction of the foam interlayer could obtain homogeneous microstructure, change stress distribution, and improve mechanical properties of the brazed joints.

Microstructure, mechanical and optical properties of MgAl2O4/MgAl2O4 joints bonded using CaO-Al2O3-SiO2 glass filler

Transparent MgAl2O4 ceramics were bonded by using CaO-Al2O3-SiO2 (CAS) glass filler. The CAS glass filler exhibited the same thermal expansion behavior as MgAl2O4 ceramic and excellent wetting ability on the surface of MgAl2O4 ceramic. When the cooling rate of 15 °C/min was used, no interfacial reaction was observed and the amorphous brazing seam could be obtained. However, low joining temperature (1250 °C) led to the formation of pores and high joining temperature (1400 °C) resulted in the formation of cracks. Furthermore, the slow cooling rate of 5–10 °C/min induced the crystallization of CaAl2Si2O8 and Mg2Al4Si5O18 due to the dissolution of MgAl2O4 substrate. The optimal flexural strength of 181–189 MPa was obtained when the joining temperature and cooling rate were 1300–1350 °C and 15 °C/min respectively. Moreover, the in-line transmittance of the joint at 1000 nm was 82.1%, which was slightly lower than that of MgAl2O4 ceramic (85.6%).

Improved mechanical strength of the C/C-Mo joint by introducing polydopamine modified Ni foam to the interlayer

For the dissimilar C/C-Mo joints, the high residual thermal stress in the joint generally leads to the low shear strength of the joint, especially when the joints are employed under the quick alternating temperature change conditions. To address this issue, three-dimensional polydopamine modified Ni foam was introduced to the C/C-Mo joints. The modification of Ni foam would avoid its complete dissolution and retain its framework after braze welding via a facile polydopamine carbonization strategy. As polydopamine modified Ni foam was introduced to the interlayer, the joint strength increased by 63%, up to 63.77 MPa. The introduction of the modified Ni foam is beneficial to improve the plastic deformation ability of the main phases in the joint, leading to the decrease of the brittleness of the braze seam. Furthermore, the residual Ni frameworks are facilitated to take full advantage of the good plastic deformation capability and energy absorption ability of the foam structure, resulting in the improved joint strength at room temperature and a high strength retention of 92.07% after 10 thermal cycles between room temperature and 1100 °C.

Joining of SiC using CoFeCrNiCuTi high entropy alloy filler by electric current field assisted sintering

SiC ceramics were brazed by electric field-assisted sintering technology using CoFeCrNiCuTi high-entropy alloy as joining filler. The effect on the interface microstructure and bend strength of brazed joints at different brazing temperature was systemically studied. The interfacial reaction was controlled by adjusting the brazing temperature. The main components in the brazing seam are high-entropy alloys FCC (HEAF), C, TiC, CrC, and Cr23C6 phase. Furthermore, the maximum bending strength of 54 MPa was found when brazed at a lower temperature of 1125℃. In addition, due to the electric field-assisted sintering technology and the high-entropy effect of the CoFeCrNiCuTi filler, the diffusion of elements and the formation of solid solution were accelerated. This suggests that the current field was beneficial to improve the inter-diffusion between the CoFeCrNiCuTi filler and SiC ceramics. Consequently, the low-temperature rapid brazing of SiC ceramics was realized, and this technology provides a new filler system for ceramic brazing.

Microstructure and mechanical properties of the C/C composite and Nb joints brazed with an active Ag-based filler metal

An active Ag-based filler metal, containing trace alloy elements of Al, Cu and Ti, was successfully applied to braze C/C composite and Nb. The microstructure and formation mechanism of the C/C composite and Nb brazed joint were investigated in this study. Moreover, the influence of brazing parameters on microstructural evolution and mechanical properties of brazed joints was evaluated. The typical interfacial microstructure of the joint obtained at 950 °C for 600 s was C/C/TiC + AlCu2Ti/Ag(s, s) + AlCu2Ti + particle Cu/AlCu2Ti + AlCuTi + (Ti, Nb)3Al + Nb(Ti)/Nb. The dispersive AlCu2Ti phase was uniformly distributed in the Ag matrix, which was a beneficial structure for the brazed joint. The shear strength of the brazed joint was sensitive to the brazing temperature and holding time, which was closely related to the TiC layer bordering the C/C composite. The thickness of the TiC layer first increased as temperature increased to 950 °C, and then decreased when temperature reached 970 °C. The carbon fiber eroded by the filler at 970 °C entered to the brazing seam and reacted with Ti, resulting the reduction of the thickness of TiC, thus damaging the strength of the joint. With extension of holding time from 300 s to 1200 s, the interface reaction became more sufficient. Therefore, the thickness of the TiC layer increased. However, at 1200 s, the over-thick TiC broke the C/C substrate because of the mismatch of coefficient of thermal expansions. The maximum shear strength of the joint (950 °C/600 s) reached 55 MPa at room temperature and 35 MPa tested at 550 °C.

Brazing of super-hard AlMgB14–TiB2 ceramic to 304 stainless steel with AgCuTi filler alloy

In this paper, super-hard AlMgB14–TiB2 composite ceramic is brazed to 304 stainless steel by using an AgCuTi foil at 820 °C–910 °C for 10 min. The typical microstructure of the joint brazed at 850 °C for 10 min is 304 steel/σ-Fe/Fe2Ti/FeTi/Ti[Cu,Fe]ss/Ag(s,s)+TiCu4+Cu(s,s)/Cu[Ti,Al]ss + TiB whiskers/AlMgB14–TiB2. The formation of Cu[Ti,Al]ss + TiB whisker layer at brazing filler/AlMgB14 interface is mainly ascribed to the reaction between AlMgB14 and active Ti. With the increase of brazing temperature, the width of the brazing seam drops remarkably, while the share of Cu (s,s) in the brazing seam is increased. The maximum shear strength of joint is ∼ 47.9 MPa when brazing at 880 °C for 10 min, the fracture occurs in the AlMgB14–TiB2 substrate adjacent to the brazing seam.

The use of a carbonized phenolic formaldehyde resin coated Ni foam as an interlayer to increase the high-temperature strength of C/C composite-Nb brazed joints

A novel carbonized phenolic formaldehyde resin (PF) resin-coated Ni foam was used as an interlayer for brazing carbon fiber reinforced carbon composites (C/C) and Nb using a Ti–Ni filler. At first, uniformly distributed carbonaceous laminae with different mass fractions on the Ni foam surface were acquired after the carbonization process by controlling the concentration of the PF solution. Afterwards, the obtained carbonaceous laminae covered Ni foam composite (C-Nif) was applied as an interlayer for brazing C/C and Nb via an assembly of C/C/Ti foil/Ni foil/C-Nif interlayer/Ti foil/Nb. The morphologies and microstructures of the carbonization product and the interfacial microstructures of the joints were investigated. The brazing mechanism has been elaborated in detail. With the help of the interconnected porous structure of the Ni foam, the distribution of the in-situ formed (Ti,Nb)2Ni particles, (Ti,Nb)C ring reinforcements as well as the Nb solid solution were uniformly obtained throughout the brazing seam. As a result, the joint residual stress was effectively released and consequently, the joint shear strength at elevated temperature (1000 °C) reached up to 33 MPa, which is 4.5 times higher than the directly brazed joint without an interlayer.

Electrochemical wetting of 3YSZ by Cu and ultrafast joining with a Ni-based superalloy

The wettability of 3 mol% yttria-stabilized zirconia (3YSZ) by molten Cu was noticeably improved by applying a direct current (DC). Furthermore, robust brazing of 3YSZ to a GH3128 superalloy using a Cu filler was achieved within seconds at 1100 °C with the assistance of a DC. When the DC flowed from 3YSZ to GH3128, the shear strength of the joints reached 225 ± 20 MPa at 1 s of energization and increased to 330 ± 30 MPa at 5 s of energization. The formation of Cu51Zr14 at the 3YSZ/Cu interface, the dissolution of Ni into the Cu filler, the dispersive distribution of fine granular (Mo, Cr, W)(Ni, Cu) in the brazing seam and the relief of residual stress by ductile (Cu, Ni) solid solution were crucial for achieving the high-strength joints. This work provides a novel and economical method for ultrafast brazing of zirconia to metals.

An ultra-high bond strength of the Cf/C composite-TC4 alloy joint brazed using pure Ni and revealing of synergetic action of multiple stress-relief mechanisms

The Cf/C composite-TC4 alloy joint brazed using traditional AgCuTi- or TiZrNiCu-based interlayers generally exhibited unsatisfactory bonding strength due to large mismatch of coefficient of thermal expansion (CTE) among the bonded materials. In this work, a pure Ni foil was designed for high-strength Cf/C-TC4 joining. The results show that liquid solidification produced the Zone 1 while solid-state phase transformation gave rise to the Zone 2 in the joint. The optimal joint bond strength received was 64.2 MPa, which was the highest reported for the Cf/C-TC4 joints. The Ni-Ti eutectic reaction imported the Ti2Ni matrix into the braze seam, creating a smooth CTE transition across the interface. Additionally, incorporation of soft phases into rigid matrix coupled with phase transformation triggered stress relief contributed to such an excellent bond strength.

Microstructural stability and mechanical properties of Al2O3/Kovar 4 J34 joint vacuum brazed using Ag-5Cu-1Al-1.25Ti (wt%) filler metal

The Al2O3 ceramic and Kovar 4 J34 alloy were effectively bonded by vacuum brazing by using an Ag-based filler metal with a composition of Ag-5Cu-1Al-1.25Ti (wt%). The typical interfacial structure of the Al2O3/Kovar 4 J34 joint brazed at 960 °C for 10 min was determined as Al2O3/Ti3(Cu, Al)3O/Ag(s, s) + Cu(s, s) + disperse AlCu2Ti/Ti2Ni + TiFe2/Kovar. The brazing parameters were observed to have a decisive effect on the microstructure evolution and variation of the mechanical properties of the Al2O3/Kovar 4 J34 brazed joints. The maximum shear strength of the brazed joints could reach 150 MPa, and the failure primarily occurred in the ceramic substrate and Ti3(Cu, Al)3O reaction layer. Moreover, the microstructural stability of the Al2O3/Kovar 4 J34 brazed joints at elevated temperatures was also investigated. After thermal cycling at 600 °C for 3 h, the interfacial structure of the brazed joint did not change obviously except for the thickening of the reaction layer, and the joint shear strength remained at 130 MPa. However, the average shear strength of the joint under the testing temperature of 600 °C was reduced to 73 MPa, and the fracture propagated along the Ag matrix of the brazing seam due to the softening of silver.

Microstructure and Physical Properties of Alloy Brazed with Filler by Mapping Scanning Analysis and Wettability Test

In this paper, a new type of AlSiMgCuNiAg filler metal was developed. The solidus temperature of the filler metal is 509.1°C and the liquidus temperature is 531.3°C. The filler metal has a good wetting and spreading effect on the surface of 6061 aluminum alloy. The CuAl2 phase in the brazing seam was greatly aggregated after brazed, while the CuAl2 phase was reduced and Mg2Si strengthening phase was formed when the brazed joints with heat treatment. The average shear strength of the brazed joint without heat treatment was 47.1MPa, and the average shear strength of the brazed joint with heat treatment reached to 108.7Mpa. The strength of the brazed joint with heat treatment was increased by about 131% relative to the strength of the brazed joint without heat treatment.

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.

Microstructure evolution and improved mechanical strength of the C/C-Mo joint by adjusting the joining temperature in a wide temperature range

In order to reduce the residual thermal stress to obtain the C/C-Mo joints with high mechanical properties, the composition and distribution of the phases were optimized by adjusting the joining temperature in a wide range. As the joining temperature increases from 1180 °C to 1380 °C, the joint strength first increases and then decreases, which reaches a maximum (47.84 MPa) at 1330 °C, 42.30% higher than the joint brazed at the common utilizing temperature of the BNi-5 filler (1180 °C). The interlayer of the joint is divided into two regions: Zone 1 with Ni-rich MoNiSi and a little Ni solid solution (Niss), and Zone 2 with Mo-rich MoNiSi and high content of Niss. As the temperature increases, the thickness of Zone 2 increases while that of Zone 1 reduces due to the phase transition from Ni-rich MoNiSi to Mo-rich MoNiSi. This microstructure evolution introduces more Niss in the joint, improving the joint strength by reducing residual thermal stress via plastic deformation. Furthermore, a Ni-based interfacial layer including complex compounds with smaller sizes in the joints brazed at higher temperature leads to the stronger bonding between C/C composites and braze. The straight fracture path along the interface changed to the tortuous path in the braze seam, leading to more energy consumption, which results in the improved joint strength. The excessive temperature (1380 °C) would lead to the big sizes of the brittle MoNiSi phase, resulting in the formation of pores and cracks in the joints and poor joint strength.

A novel joining of Cf/C composites using AlCoCrFeNi2.1 high-entropy brazing filler alloys

A novel brazing of C f /C composites was achieved using AlCoCrFeNi 2.1 high-entropy alloys (HEAs) as the interlayer. The microstructure and shear strength of the joints brazed under different processing parameters was evaluated. The typical structure of the C f /C composite joints could be described as C f /C / zone 2/ zone 1/ zone 2/ C f /C. The zone 1 was a continuous metallic layer which was mainly composed of the BCC and M 7 C 3 coupled with some FCC and γ՛ phases. The zone 2 was actually a mixture of discrete graphite and filling phases. The filling phases was dominated by the FCC with embedded γ՛, while a small amount of the BCC and M 7 C 3 was also incorporated. The formation of M 7 C 3 and transformation of the FCC to BCC took place in the solid interlayer in initial heating, and simultaneously some porous graphite appeared at the substrate/interlayer interface. Upon cooling, the liquid in the middle of the braze seam was solidified to generate the zone 1, while the liquid pouring into the porous structure beside the interlayer gave rise to the zone 2 in the joint. Elevating the brazing temperature could increase the average shear strength of the joints because it accelerated the liquid penetration filling the porosities in the zone 2 and also produced a hybrid structure in the joints. In this work, the highest shear strength of the joints achieved 21.9 MPa when brazed at 1440 °C for 10 min. The hybrid structure observed showed particular role in mitigating the thermal residual stresses, providing a unique idea in joining carbon-based materials as well as extending the application of C f /C composites. • The AlCoCrFeNi 2.1 HEA interlayer was first adopted to join the C f /C composites. • The optimum joint strength reached 21.9 MPa produced at 1440 °C for 10 min. • The HEA interlayer wetted the C f /C composites through the dissolutive mode. • Rising brazing temperature produced hybrid structure to reduce residual stresses.

Interface behaviour of brazing seam of contact-reaction brazing an AZ31 magnesium with amorphous filler metal

In order to achieve brazing of magnesium alloy without brazing flux, a new AlSiCu amorphous alloy was designed as an intermediate layer. The contact reaction brazing method was used to brazing AZ31 magnesium alloy with AlSiCu amorphous alloy as an intermediate layer. The SEM and OM methods were used to analyze the structure of the brazing seam, and it was found that there were block, granular, and dendritic alloy phases in the brazing seam. The composition of the alloy phases in the brazing seam was measured by EDS analysis, and the intermetallic compounds of Mg Al were found. Unfixed micro-holes were found in the brazing seam held at 450 °C for 15 min, and these micro-holes disappeared and a complete interface connection was formed in the brazing seam when the holding time increased to 20 min. With the increase of brazing time, the brazing seam became wider and the dendrite in the brazing seam began to spread towards the base metal and gradually decreased after holding for 25 min. After holding for 30 min, the dendrite disappeared and the second phase appeared as granular and short rod distribution, and the number decreased significantly. The joint strength increases significantly with the increase of holding time, and the tensile shear strength of the lap joint is 110 MPa. The average hardness of the brazing seam is 94.2 HV, the hardness values of the matrix phase and the second phase are different greatly. The probe was used to analyze the microstructure and morphology of the shear fracture, and it was found that cleavage patterns and dimples existed on the fracture surface at the same time. • The contact reaction brazing method is used to achieve the brazing connection of the AZ31 magnesium alloy. • The AlSiCu amorphous alloy is used as the intermediate layer, and the tissue performance of the joint is improved. • By means of diffusion and differentiation, the shape of the MgAl compound in brazing seam is changed.