Aluminum surface texturing by means of laser interference metallurgy

The increasing use of lightweight materials, such as aluminum alloys, in auto body structures requires more effective surface cleaning and texturing techniques to improve the quality of the structural components. The present work introduces a novel surface treatment method using laser interferometry produced by two beams of a pulsed Nd:YAG laser operating at 10Hz of frequency to clean aluminum surfaces, and meanwhile creating periodic and rough surface structures. The influences of beam size, laser fluence, wavelength, and pulse number per spot are ¹]. Aluminum surface cleaning to remove oxides and contaminations is required prior to the welding and joining processes. Without proper surface preparation, seams and joints are susceptible to increased wear, degradation and, in some cases, catastrophic failure. There are many methods to remove aluminum surface oxides. Mechanical method [²] is one prevalent method due to its relative low cost. It typically uses blasting media or abrasive materials that are applied directly to the surface. Chemical stripping [³] is another widely used cleaning method. An advantage of this method is the ability to more easily remove all traces of surface oxides and contaminations regardless of shape or surface features. Although the chemical stripping method is effective, the cost associate with environmental protection, hazardous-waste management is high. High-energy laser pulses can also be used for surface cleaning [⁴,⁵]. The mechanism is mainly due to the surface melting and ablation when the metal surface subjected to very short laser pulses (nanoseconds to milliseconds range) with high peak intensities, as well as the laser-induced shocks [⁶]. It's a non-contact process without abrasion and chemical impact. The controllability offered by laser enables high-precision removal of surface oxides and contaminations in the range from sub-micrometers to several millimeters. All types of organic and inorganic impurities can be removed from the surface. This paper introduces another method for aluminum surface processing using laser interference patterning. The interface pattern is produced by two beams of high-energy laser pulses. Like the conventional laser cleaning method, surface oxides and contaminations are likely to be removed. Meanwhile, periodic structures can be formed on the surface due to the periodic intensity distribution of the laser interference patterns. This method offers the capability to control the surface texture.