. (2014) The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture. Optics and Laser Technology, 64 . pp. 162 171. ISSN 0030 3992 It is advisable to refer to the publisher's version if you intend to cite from the work. This paper reports the effects of short pulsed laser surface cleaning on the porosity formation in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning.The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23 -0.8% from 0.7 -4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation.2

AC-170PX (AA6014) alloys are typically used in lightweight automobile vehicles. Laser welding can be a viable tool for the assembly of components. However, porosity is often generated during aluminium welding. In this article, an investigation is reported on the characteristics of porosity formation in high-power disc laser welding of AC-170PX aluminium alloy sheets in two weld joint configurations: fillet edge and flange couch with three different filler wires of 4xxx, 3xxx and 5xxx aluminium series for each joint. Porosity, microstructures, tensile strengths and joint geometry were investigated. It has been found that the use of filler wires with higher Mg and Mn content such as AA5083 and AA3004 leads to a significant reduction in porosity to less than 1.5% in both types of joints compared with up to 80% porosity with the silicon-rich AA4043 wire. The mechanism that led to this improvement is discussed.

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Changing material surface micro/nano structures using laser beam texturing is a valuable approach in wide applications such as control of cell/bacterial adhesion and proliferation, solar cells and optical metamaterials. Here we report a comparison of the characteristics of surface micro/nano structures produced using single beam laser direct writing and particle lens array parallel laser beam patterning. A Nd:YVO4 nanosecond pulsed laser at 532 nm wavelength was used in the laser direct writing method to texture the stainless steel surface submerged in water and in air with different scanning patterns. Changes in surface morphology, wettability, surface chemistry and optical reflectivity were analyzed. In the particle lens array method, an excimer nanosecond laser at 248 nm wavelength was adopted to produce surface patterns on GeSbTe (GST) film coated on a polycarbonate substrate by splitting and focusing a single laser beam into millions of parallel breams. Single beam laser direct writing shows that the surface of high roughness and oxygen percentage content presented high wettability and low reflectivity characteristics. However, the controllability of the type of surface micro/nano patterns is limited. The parallel laser beam processing using particle lens array allows rapid production of user designed periodic surface patterns at nano-scale overcoming the optical diffraction limit with a high degree of controllability. Controlling the uniformity of the particle lens array is a challenge.