Junhui Chen

Cold metal transfer welding-brazing of magnesium to pure copper

Abstract Magnesium alloy AZ31B and pure copper T2 were lapped and joined by cold metal transfer (CMT) welding–brazing method by AZ61A magnesium alloy wire with a 1·2 mm diameter. Results indicated that a satisfied Mg/Cu CMT welding–brazing joint was obtained in the stable welding processes with no spatter. The joint was composed of Mg–Mg welding joint formed between the Mg weld metal and the Mg base metal, and Mg–Cu brazing joint formed between the Mg weld metal and the local molten Cu base metal. The microstructure and the intermetallic compound (IMC) distribution were inspected and analysed in detail. The interfacial reaction layers of the brazing joint consisted of Mg2Cu, Al6Cu4Mg5, MgCu2 and Mg17Al12 IMCs. The tensile shear strength of the Mg/Cu CMT welding–brazing joint could reach 172·5 N mm−1. In addition, two different fracture modes were observed: at the fusion zone and at the brazing interface.

Wetting of steel by Al 4043 alloys in cold metal transfer process

Abstract The sessile drop method was used for the study of the wetting of steel by Al 4043 alloys in cold metal transfer process. The moving of triple line was determined by the reaction at interface rather than the wettability of reaction product. The evaporation of Zn coating for galvanised steel induced instability of wetting for small wire feed speeds and reduced the heat input in the interface. Wire feed speed dependent interfacial structures were observed, which are due to the heat input dependent interfacial reactivity. The calculation of adsorption energy can be used for the explanation of interfacial structures and Zn rich zone in Al galvanised steel system.

The Magnetism Properties and Surface Microstructure of NBR/Fe3O4 Composites

For preparing the good magnetism properties of rubber, NBR/Fe3O4 composites are prepared. In the experiment, the surface microstructure of NBR/Fe3O4 and distribution of nano-Fe3O4 particles are analyzed. The results showed that after the addition of nano-Fe3O4, the surface microstructure of NBR/Fe3O4 is greatly improved. The interface bonding of nano-Fe3O4 and NBR are close-knit. With adding different mass fractions of nanoparticles, the maximum elongation 300% stress at definite elongation and the tensile strength of composites are decreased, but the shore A hardness of composites is improved. The magnetic property of composites can only rely on mass fraction of nano-Fe3O4, while uncorrelated to the degree of scatter of nano-Fe3O4.

Effects of zinc coating on magnesium alloy–steel joints produced by cold metal transfer method

Magnesium alloys are lap-joined to galvanised and bare steel sheets by a cold metal transfer method. The weld appearance, cross-section, tensile strength and fracture behaviour of these joints are characterised by scanning electron microscopy, tensile tests and energy-dispersive spectroscopy. The joints were found to have good weld appearance and satisfactory tensile strength. The spreadability and wettability of the Mg alloy–galvanised steel joint are superior to those of the Mg alloy–bare steel joint, but the tensile strength is lower. In particular, the presence of Zn on the galvanised steel sheet improves wettability but decreases tensile strength. Aluminium has a high affinity for Fe, and the thinner layer of Fe–Al improves the mechanical properties of the Mg alloy–bare steel joint.

Coupling Analysis on Thermoviscoelastic Constitutive of Nano-Fe3O4 Reinforced Nitrile Butadiene Rubber

Nano-Fe3O4 reinforced nitrile butadiene rubber (NBR) samples were prepared, and the distribution of nano-Fe3O4 particles was mensurated. Using the split Hopkinson pressure bar with an electronic temperature control device and the SHS4-VS1 dynamic fatigue tester, stress–strain curves of NBR/nano-Fe3O4 composites with different mass fractions of nano-Fe3O4 were measured at −30°C to 60°C and different strain rates (1 × 10−3/s to 3 × 103/s). Based on the nonequilibrium thermodynamic theory, we analyzed the thermoviscoelastic constitutive of NBR/nano-Fe3O4 composites, got free energy expression of decoupling form between thermal effects and mechanical effects, and put forward a constitutive model which can describe one-dimensional compressive force at different temperatures and different strain rates.

Study on Magnetic and Physical Mechanical Properties of NBR Composites Filled with Nano-Sro•6Fe2O3

In this study, we used nano-SrO.6Fe2O3 particles as modified filler to prepare nitrile butadiene rubber/SrO.6Fe2O 3 composites. Surface microstructure of the composites was observed using scanning electron microscope, the distribution of nano-SrO.6Fe 2O3 particles was measured by energy-dispersive X-ray spectrometer, and magnetic properties of the composites were tested by a U5-10 magnetizer. The results showed that nano-SrO.6Fe2O3 particles were closely inosculated with nitrile butadiene rubber and well distributed in the nitrile butadiene rubber matrix. With adding different mass fractions of nano-SrO.6Fe2O3, stress at 300% definite elongation, maximum elongation, and tensile strength of the composites were slightly decreased, but shore A hardness of the composites was markedly improved. Magnetic properties of the composites were uncorrelated to the degree of scatter of nano-SrO.6Fe2O3 particles, and relied only on mass fraction of nano-SrO.6Fe2O3 particles. The nitrile butadiene rubber/SrO.6Fe2O3 compo...In this study, we used nano-SrO 6Fe2O3 particles as modified filler to prepare nitrile butadiene rubber/SrO 6Fe2O3 composites. Surface microstructure of the composites was observed using scanning electron microscope, the distribution of nano-SrO 6Fe2O3 particles was measured by energy-dispersive X-ray spectrometer, and magnetic properties of the composites were tested by a U5-10 magnetizer. The results showed that nano-SrO 6Fe2O3 particles were closely inosculated with nitrile butadiene rubber and well distributed in the nitrile butadiene rubber matrix. With adding different mass fractions of nano-SrO 6Fe2O3, stress at 300% definite elongation, maximum elongation, and tensile strength of the composites were slightly decreased, but shore A hardness of the composites was markedly improved. Magnetic properties of the composites were uncorrelated to the degree of scatter of nano-SrO 6Fe2O3 particles, and relied only on mass fraction of nano-SrO 6Fe2O3 particles. The nitrile butadiene rubber/SrO 6Fe2O3 composites have good soft magnetism performance, which laid the foundation for further application of the composites. *Author to whom correspondence should be addressed. E-mail: wangqilei500@yahoo.com.cn JOURNAL OF ELASTOMERS AND PLASTICS Vol. 43–May 2011 275 0095-2443/11/03 0275–10

Cold metal transfer spot plug welding of AA6061-T6-to-galvanized steel for automotive applications

10.00/0 DOI: 10.1177/0095244310393928 The Author(s), 2011. Reprints and permissions: http://www.sagepub.co.uk/journalsPermissions.nav