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Dissimilar joints of copper to aluminium were produced by high power ultrasonic welding (USW). The interfacial reaction between copper and 6061 aluminium alloy as a function of welding time was studied. The intermetallic compound (IMC) layer is mainly composed of CuAl 2 and Cu 9 Al 4 . The thickness of the IMC layer increases with the welding time. For a relatively long welding time (0?7 s) in USW, the dendritic solidification microstructure was observed in local regions, owing to the occurrence of the eutectic reaction, a-AlzhRL, in the welding process. The lap shear load (or strength) of the joints first increases and then decreases with increasing welding time, and the failure of the joints occurred dominantly at the interface. This is mainly attributed to the development of IMC layer at the interface.

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Titanium boron nitride (Ti-B-N) films with various boron contents were deposited using titanium and boron targets in a reactive magnetron sputtering system. The boron content in the film was varied from 0 at.-% to 8.7 at.-%, to evaluate its properties. Various analytical techniques such as X-ray diffraction, high-resolution electron microscopy, nanoindentation and ball-on-disk dry sliding etc. were used. Incorporation of B into the film influenced the microstructure, mechanical and room-temperature tribological properties. At a B content of 0.2 at.-%, the film exhibited the highest hardness of ∼27 GPa. It also presented the lowest wear rate of ∼2.9 × 10 −7 mm 3 N −1 mm −1 . However, there was a gradual decrease in coefficient of friction (CoF) values of the film when the B content was increased, with a minimum of 0.2 attained at 8.7 at.-% boron. The increased volume fraction of amorphous boron nitride phase contributed to the decrease in coefficient of friction.