Semi-solid Brazing Research Articles

Mechanism of oxide film removal and analysis of diffusion behavior of interfacial elements during magnetic pulse-assisted semi-solid brazing

The magnetic pulse-assisted semi-solid brazing (MPASSB) for Cu/Al tubes is proposed, in order to effectively remove oxide film to ensure the metallurgical bonding of Cu/Al brazing and joint performance. By designing a field shaper with a specific taper angle, the axial distribution of the electromagnetic force, tube deformation, and filler metal shear rheology are controlled to obtain the interface joining characteristics under different mechanical conditions. The relationship between the deformation behavior of the tube and filler metal with the interface element diffusion and metallurgical bonding is analyzed through the forming process simulation and interface microscopic characterization. In addition, the mechanical mechanism of oxide film removal is discussed as well. The results show that metallurgical bonding and element diffusion depend on the comprehensive effect of the interface compressive stress and the shear rheology of the filler metal. The larger the compressive stress, the better the oxide film removal. The stress at the bottom Cu/filler metal interface is the weakest, with an oxide layer thickness of 11.5 µm. The higher the shear rheological rate, the less the element diffusion depth. The filler metal flow rate at the bottom Cu/filler metal interface is the slowest, with a maximum depth of element diffusion of 13.5 µm. On the premise of ensuring the effective removal of the oxide film, the shear rheological rate (compressive stress) should not be too high.

Ultrasonic-Assisted Semi-Solid Forming Method and Microstructure Evolution of Aluminum/Copper Brazed Joints

Aluminum/Copper dissimilar metal connection devices have been widely used in equipment manufacturing. Ultrasonic vibration assisted semi-solid brazing technology is beneficial to improve brazing quality by using the good flow ability and strong deformation resistance of brazing alloy when it is in a semi-solid state. In this study, a new ultrasound-assisted high-frequency induction brazing method was used to braze aluminum and copper dissimilar metals under non-vacuum conditions with non-prefabrication of brazing filler metal. In a short time, uniform semi-solid brazed joint was obtained. Detailed investigations on the effects of aluminum-substrate side (Abbreviated as Al side) heat dissipation rate and ultrasonic vibration duration on the microstructure evolution and mechanical properties of semisolid weld were conducted. The results show that the welding seam obtained by the modification method increases the microstructure uniformity of brazing joint.

Joining of Mn-Cu alloy and 430 stainless steel using Cu-based filler by SIMA-imitated brazing process

A new SIMA-imitated brazing was used to join Mn-Cu damping alloy and 430 stainless steel (SS) with Cu-34Mn-6Ni-10Sn filler metal. The microstructure and mechanical properties of the brazed joint were investigated. The results show that the semi-solid brazing seam was obtained at 790 °C. A (Fe, Mn, Cr) solid solution diffusion layer was formed between 430SS and brazing seam. The Mn-Fe-Cu-Cr compounds were formed in brazing seam due to the dissolution of 430SS. The liquid phase penetrated along the grain boundaries of Mn-Cu alloy. The shear strength of the brazed joint is 230 MPa, the brazed joint exhibits a ductile fracture feature.

Reduction of intermetallic compounds in ultrasonic-assisted semi-solid brazing of Al/Mg alloys

ABSTRACTAn ultrasonic-assisted semi-solid brazing method was used to control Mg/Al intermetallic compounds (IMCs). Zn–20.95Al, which has a large semi-solid temperature range of 60°C, was chosen as filler metal. Oxide films on the Al/Mg surfaces were removed despite the semi-solid state of the filler metal at 430°C. Al–Mg–Zn IMCs were observed inside the joint at 667 W and 5 s. The IMCs was reduced as ultrasonication time was prolonged. At high power of 1000 W, short ultrasonication time was needed to guarantee that no IMCs remained inside the joint. Otherwise, new IMCs formed because of serious cavitation erosion on substrates. Ultrasonication time of 20 s was unable to completely eliminate IMCs and solid phases at 423°C.

Application of a new ultrasonic-assisted semi-solid brazing on dissimilar Al/Mg alloys

In this work, an ultrasonic-assisted semi-solid brazing method was proposed to join Al/Mg. Oxide films on substrate surfaces can be successfully removed even when filler metal was at semi-solid state. A large quantity of intermetallic compounds (IMCs) formed at 460 °C because of large amount of Al and Mg dissolved into joint caused by strong cavitation. Decreasing the temperature to 430 °C could significantly reduce IMC. However, weak cavitation happened inside low liquid phase fraction at 420 °C, making it difficult to break IMCs and solid phases.

Behaviors of Oxide Film during Semisolid Brazing of SiCp/6063Al Composite Materials

The semisolid brazing of SiCp/6063Al under an applied pressure using Zn‐Al‐Cu filler metal was investigated. The samples to be joined were heated from 380°C to 382°C, 386°C, 392°C, and 410°C under a constant pressure of 10 MPa, respectively. Effects of the temperature on microstructural evolution and deformation behavior of the filler metal, interfacial structure, and shear strength of the bonded joint were discussed, and the disruption behavior of the surface oxide film was studied. The results show that, after heating, the solid grains of the filler metal transform into a globular structure surrounded by liquid. The degree of sphericity and the liquid fraction tend to improve with increasing temperature. During the heating process, the deformation of the filler metal is first accomplished by plastic deformation of solid grains and then by intergrain sliding and liquid flow. The surface oxides are broken and stripped by a cocontribution of compressive and shear stress which is caused by depressing and sliding of solid grains along the composites. It is found that the heating of 380°C to 392°C under pressure is the optimum condition to disrupt the surface oxide films and obtain sound bonds. The mechanical test results show that the maximum shear strength of the bond joints is as high as 105 MPa, reaching 78% that of the parent materials.

Semisolid stirring brazing of SiCp/A356 composites with Zn27Al filler metal in air

The semisolid brazing process of SiCp/A356 composites was investigated. The effects of temperature on the microstructure of the filler metal and the joints are discussed in this paper. The research results show that with increasing temperature, the solid fraction of the filler metal decreases. Moreover, the SiCp/A356 composites can be effectively joined with the semisolid filler metal by optimising the stirring temperature. It can be found that most of the oxide film on the surface of the composites is disrupted by mechanical stirring. In this case, the metallurgical bonds formed at the interface between the filler metal and the base materials. Since the semisolid temperature range of the filler metal is narrow, the accurate controlling of the weld pool temperature must be considered.

Deformation behavior of semi-solid Zn–Al alloy filler metal during compression

► Semi-solid Zn–Al alloy discs with a ( h / d ) of 0.6, 0.3 and 0.1 were compressed. ► A comparison was made of their stress–strain curves during compression. ► Shape changes of the solid grains in the discs during compressions were examined. ► Interactions on the contact surface during disc compressions were analyzed. ► Discs were used as a filler metal in the semi-solid brazing of SiCp/Al composites. We investigated the compression of a semi-solid Zn–Al alloy disc as it is often used as a filler metal to braze aluminum alloys and their composites. Three different size discs were used with height-to-diameter ratios ( h / d ) of 0.6, 0.3 and 0.1. Stress–strain curves were obtained during disc compressions. The maximum stress obtained during the compressions increased with a decrease in disc size ( h / d ). Configuration changes of the solid grains in the semi-solid Zn–Al alloy discs were examined during the compressions. There exist a hard deformation area with slight changes in grain shape and a severe deformation area with significant changes in grain shape on the contact surface of the discs. And with a decrease in disc size ( h / d ) the severe deformation area enlarged and the hard deformation area dwindled from the edge towards the center during the compression. Interactions of the semi-solid Zn–Al alloy disc with the compressing block on the contact surface during a compression was qualitatively analyzed on the basis of the solid grains’ action in the different deformation areas. For the smaller disc ( h / d ) the contact surface interaction showed an intense compression in the center and a combination of shearing and compression over the remainder of the surface during the compression. This was beneficial to the disruption of the oxide film on the contact surface for the semi-solid brazing of SiCp/Al composites when the disc was used as a filler metal.

Study of Brazeability of SiC<sub>P</sub>/A356 Composites and Aluminum Alloy Using Semisolid Metal with High Solid Fraction by Stirring

The semi-solid brazing process of SiCp/A356 composites and 2024 aluminum alloy using Zn-Al eutectic filler metal at 450 °C has been investigated. The two substrates and Zn-Al filler metal were heated up to the semisolid temperature range of Zn-Al filler metal by a resistance heating plate. In order to mix the filler metal with the base metal of both sides to be a single uniform joint, a stirrer was introduced into the weld seam. After stirring, specimens were sectioned for analysis of macro- and micro-structures along the weld region. The research shows that SiCp/A356 composites and aluminum can be joining by semisolid metal. It can be found that almost half of the oxide film on the surface of the base metal was disrupted and removed through the observation by SEM. The metallurgical bonds formed between the filler metal and the base materials on the interface of oxide had been disrupted. Moreover, the oxide film of surface of aluminum alloy was more thoroughly disrupted and removed than that of surface of composites with existing of SiC particle.

Semi-Solid Stirring Brazing of SiCp/A356 Composites and Aluminum Alloy in Air

The semi-solid brazing process of SiCp/A356 composites and aluminum alloy was investigated. The two substrates were heated up to the semisolid temperature range of Zn-Al filler metal in the joint region by a resistance heating plate. At this point a stirrer was introduced into the weld seam in order to mix filler metal and the two sides of substrates into a single uniform joint. After stirring, specimens were sectioned for analysis of macro- and micro-structures along the weld region. The research shows that SiCp/A356 composites and aluminum can be successfully joining with semi-solid filler metal. It can be found that most of the oxide film on the surface of the base metal was disrupted and removed through the observation by SEM. The metallurgical bonds formed between the filler metal and the base materials. Moreover, the oxide film of surface of aluminum alloy was more thoroughly disrupted and removed than that of surface of composites with existing of Sic particle. The joint microstructure with globular α-Al grain enclosed by rich-Zn phase can be obtained after stirring brazing.