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Joining technology of lightweight dissimilar metals between magnesium and aluminum alloys is essential for realizing hybrid structure cars and other engineering applications. In the present study, the normal center-line welding of lap joint was carried out by laser welding. It was found that the intermetallic layer formed near interface between two metals significantly degraded the joining strength. FEM heat transfer analysis was carried out to find out an available method to control penetration depth and width of molten metal, which contributes to control thickness of intermetallic compound layer. Based on the results of FEM analysis, the edge-line welding of lap joint was carried out, which could easily control the thickness of intermetallic layer and successfully obtained high joining strength. q

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The weld strength of thermoplastics with aluminium alloy, such as high density polyethylene and polypropylene sheets, is influenced by friction stir welding parameters. This paper focuses on the preliminary investigation of joining parameter at various levels as well as the mechanical properties of friction spot joining (FSJ) of aluminium alloy (A5052) to polyethylene terephthalate (PET). A number of FSJ experiments were carried out to obtain optimum mechanical properties by adjusting the plunge speed and plunge depth in the ranges of 5-40 mm min 21 and 0?4-0?7 mm respectively, while spindle speed remains constant at 3000 rev min 21 . The results indicated that A5052 and PET successfully joined with the aid of frictional heat energy originated from the friction spot welding process. The effect of plunge speed on the joined area and the effect of formation of bubbles at the interface of joints on the shear strength of joint are discussed.

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Bioactive coatings on cp-Ti and Ti-6Al-4V were prepared by a simple chemical technique. Specimens of cp-Ti and Ti-6Al-4V were initially immersed in a 5 M NaOH solution at 60 degrees C for 24 h which resulted in the formation of a porous network structure composed of Na2Ti5O11 and TiO2. The specimens were then immersed in a Ca-rich solution either at 60 degrees C or at 36.5 degrees C for 24 h. During this treatment Na+ was released and Ti-OH groups were formed. Subsequently, TiO2 dissociated from the Ti-OH group and combined with calcium ions to form calcium titanate (CaTiO3), which was embedded in a titania gel layer during the immersion period. The specimens were then immersed in r-SBF at 36.5 degrees C for 1-30 days. After immersion in r-SBF for 3 days, HAp (hydroxyapatite) spheroids began to deposit on the substrates, and within a week the surfaces were covered. The HAp spheroids were 5 microm in size with a Ca/P ratio of 1.68 which was close to bone-like apatite (1.67). The average thicknesses of HAp layer after immersion in r-SBF for 3 days, 1 week, and 2 weeks were 3.8, 5.6, and 6.4 microm, respectively. A scratch test, used to evaluate the adhesive strength of the HAp layer, showed that the HAp layer was not scraped off until the applied load reached 26 N.

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