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In this paper, the weldability of AA 5083-H111 (non-heat treatable) and AA 6082-T6 (heat treatable) aluminium alloys, which are widely used in welding fabrication, is compared by analysing the welds obtained from both materials under a large range of welding conditions (varying tool dimensions, rotation and traverse speeds, axial loads and tilt angles) chosen to ensure high welding speeds. The differences in friction stir weldability, assessed by weld defect analysis and weld strength characterisation, will be related to the markedly different plastic behaviours of both base materials. Based on the experimental results, a methodology for determining suitable friction stir welding parameters is proposed.

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The application of laser cleaning to paintings is relatively recent despite its use on stone-based materials for over 30 years. The cleaning of paintings is of high importance, because it is the least reversible invasive intervention, as well as the most usual of all conservation treatments. Paintings are multilayer system of heterogeneous nature, often very sensitive and inherent difficult to clean. Being a noncontact method, laser cleaning has advantages compared to alternative techniques. Over the last decade, there have been important research studies and advances. However, they are far from sufficient to study the effects on painting materials and to establish the best parameters for each material under investigation. This paper presents a historical overview of the application of laser technology to the cleaning of paintings giving special emphasis on the research of the last decade. An overview of the current research into the interaction between the radiation and the different painting materials (varnish, pigments, and medium) is also given. The pigment's mechanisms of discoloration and the presence of media as a variable factor in the discoloration of pigments are discussed.