Shiqin Yang

Vacuum hot roll bonding of titanium alloy and stainless steel using nickel interlayer

Abstract Vacuum hot roll bonding of titanium alloy and stainless steel using a nickel interlayer was investigated. No obvious reaction or diffusion layer occurs at the interface between stainless steel and nickel. The interface between titanium alloy and nickel consists of an occludent layer and diffusion layers, and there are the intermetallic compounds (TiNi3, TiNi, Ti2Ni and their mixtures) in the layers. The total thickness of intermetallic layers at the interface between titanium alloy and nickel increases with the bonding temperature, and the tensile strength of roll bonded joints decreases with the bonding temperature. The maximum tensile strength of 440·1 MPa was obtained at the bonding temperature of 760°C, the reduction of 20% and the rolling speed of 38 mm s–1.

Vibration characteristics of aluminum surface subjected to ultrasonic waves and their effect on wetting behavior of solder droplets.

The vibration characteristics of an aluminum surface subjected to ultrasonic waves were investigated with a combination of numerical simulation and experimental testing. The wetting behavior of solder droplets on the vibrating aluminum surface was also examined. The results show that the vibration pattern of the aluminum surface is inhomogeneous. The amplitude of the aluminum surface exceeds the excitation amplitude in some zones, while the amplitude decreases nearly to zero in other zones. The distribution of the zero-amplitude zones is much less dependent on the strength of the vibration than on the location of the vibration source. The surface of the liquid solder vibrates at an ultrasonic frequency that is higher than the vibration source, and the amplitude of the liquid solder is almost twice that of the aluminum surface. The vibration of the surface of the base metal (liquid solder) correlates with the oxide film removal effect. Significant removal of the oxide film can be achieved within 2s when the amplitude of the aluminum surface is higher than 5.4 μm or when the amplitude of the liquid solder surface is higher than 10.2 μm.

Modelling behaviour of oxide film during vibration diffusion bonding of SiCp/A356 composite in air

Abstract The vibration liquid phase diffusion bonding of SiCp/A356 composite in air has been investigated. The surface of specimens to be bonded was treated with and without vibration under the bonding condition. It was found by atomic force microscopy analysis that some of the oxide film could be broken down when ridges on the surface of the matrix were ground down. Dissolution of the base metal by the filler metal occurred with removal of the oxide film during vibration liquid phase bonding, and SiC particles in the base metal entered the bond region. A removal process model for vibration bonding has been established with and without filler metal. Results show that shearing and impacting actions are the two main breaking mechanisms during vibration; the oxide film bulk is generally broken down by shear, and dissolution of the base metal by the filler metal promotes particle segregation from the matrix and their entry into the bond region.

Microstructure and mechanical performance of GTA weld brazed joints of copper thick plates

Abstract The gas tungsten arc (GTA) weld brazing of 10 mm copper thick plates without preheating was investigated. The filler metal of Cu–Ag–P eutectic alloy was used in the experiments. The GTA weld brazing and brazing were compared on the microstructure and mechanical performance of their joints. It can be found that the base metal is largely dissolved by the filler metal in the case of infusion of the copper, and the α-Cu solid solution in the weld metal for weld brazing is larger than that in the weld metal for brazing. The average hardness of the weld metal for weld brazing is 50 HV lower than that for brazing. The impact ductility for weld brazing is almost thrice of that for brazing.

Interfacial structure and formation mechanism in ultrasonically aided liquid bonding of Al18B4O33/Al composites in air

Abstract Alumina borate whisker reinforced aluminium metal matrix composites were liquid bonded in air. The liquid filler metal of a Zn–Al eutectic alloy could get into the clearance between composites couples by the action of ultrasonic capillarity. The bond/composite interface was eroded, so that a rough interface formed and the oxide film could be removed completely under the action of ultrasonic vibration for 3 s. The shear strength of the bond increases with ultrasonic time. A removal model for the oxide film on the composites during ultrasonic aided liquid bonding was established.