Papers by Keyword: Interface Morphology

Abstract: This paper presents the results of the effect of ultrasound on explosion welded materials. It was found that simultaneous treatment with ultrasonic vibrations and explosion welding of the materials to be welded has a significant effect on the structure and properties of the heat-affected zone of formed aluminum and copper joints. It has been experimentally proved that the change in the sizes and structure of the weld junction during explosion welding using high-frequency vibrations is a result of the simultaneous action of these processes at the stage of joint formation and hardly depends on the structure of the material.

Abstract: Laser impact welding (LIW) is a novel welding technique which uses laser induced shock waves to obtain the solid-state and metallurgical bonding between flyer and base plates, and can be applied in welding of dissimilar metal plates in micron level. In this paper, experimental study is conducted with titanium as the flyer plate and aluminum as the base plate under different laser energies and laser spot diameters. Besides, the microstructure and mechanical properties of the welding joints are also investigated. The wavy interface is observed by metallographic investigation which is similar to explosive welding and electromagnetic pulse welding. Moreover, the micro-hardness taken from the interface region shows an obvious improvement compared with the base metal. It is also found that laser shock welding results in fine grained structure of titanium on the weld interface. In conclusion, laser shock welding can not only improve the material microstructure of weld interface, but also avoid the heat affected zone and formation of intermetallic phase during dissimilar metal welding. Therefore, it is a promising welding technology in the field of MEMS.

Abstract: In order to improve the mechanical properties of poly (lactic acid) (PLA), cotton fiber/PLA composites were prepared by melting compounding and injection molding. The effects of cotton fiber content and coupling agent on mechanical properties, crystalline behavior and interface morphology of the composites were studied by universal testing machine, DSC and SEM, respectively. The results showed that the crystallinity of the composites increased gradually with the increase of cotton fiber content, whereas the mechanical properties of the composites increased firstly and then decreased with further addition of cotter fiber. The composite with 20wt% cotton fiber had an optimal mechanical performance. In addition, with the incorporation of 1wt% coupling agent, the interfacial adhesion between cotton fiber and PLA improved obviously, and the mechanical properties of the composites increased accordingly. Compared with the neat PLA, the tensile strength, flexural strength, flexural modulus and impact strength of the resultant composites were increased by 66.0%, 27.4%, 45.8% and 60.4%, respectively.

Abstract: This paper investigates the interaction between the convective flow induced by the straining flow and the interface morphology of a particle growing in the convective undercooled melt. The resulting approximate solution of the particle shape shows that the convection makes the growing particle enhance its growth velocity and protrude near the surface where the flow is incoming, but decreases its growth near the surface where the flow is outgoing, and both the incoming flow and the anisotropic surface tension make the velocity of the particle have a superposition effect along the favorite crystalline direction. The convection makes the particles growing in the undercooled melt evolve into various shapes of the interface morphology which have high strength/weight ratio and specific surface fraction and then help to form the final material of excellent mechanical and physical properties.

Abstract: The bubble structures, fishscaling resistance, adhesion and its mechanism of vitreous enamel to low carbon steels were evaluated by microscopic methods. The results show that the microalloying elements deteriorates the adhesion but suppress the fishscaling tendency, the enamel-steel interface adhesion could be explained as mainly the mechanical interlocking and chemical bonding during the firing process; the lower carbon substrate causes higher proportion of bigger bubbles in the enamel layer and subsequently causes the lower fishscaling susceptibility.

Abstract: The morphology of the interface between a commercial epoxy prepreg resin (HexPly M18/1) and Polyetherimide (PEI) is studied. Different cure cycles prescribed by the supplier were investigated to determine the influence of temperature and pressure on interface formation. Atomic Force Microscopy (AFM) was used as the main means of investigation. A phase-separated interphase spanning 9-10μm was observed for the PEI/epoxy prepreg interface. It was found that the temperature profile of the cure cycle strongly influences the formation of this interphase. Rapid formation of these relatively large interphase areas suggests that mechanisms other than diffusion are responsible for this phenomenon.

Abstract: In the present study, the effect of injection temperature, velocity and delay time on the interface morphology of the co-injection molded plates was studied. The results showed that the core penetration parallel to the flow direction becomes less as the skin injection velocity and temperature increases and delay time decreases. Among the parameters, temperature was the most significant in affecting the interface morphology, followed by delay time, while injection velocity seemed to play no significant role. The results were analyzed by taking account of rheological properties of the two feedstocks. Calculations and comparisons of viscosity ratios encountered in experiments were made. It was demonstrated the differences in the rheological properties of the metal feedstocks involved are key factors in determining the interface morphology of the molded parts.