Laser Bending of 5005 Aluminum Alloy Sheets

Introduction

Laser bending can be considered a valid alternative to traditional mechanical bending in the case of small production runs and prototyping. Nevertheless, efficiency of this laser process strongly depends on the adopted laser source, the process set-up and the material to bend. Good results are obtained for steel sheets also in complex forming operations (Guglielmotti, 2009) whereas aluminum alloys do not behave in an optimal way because of the high thermal conductivity and the high heat sensibility (Chang, 2000; Casamichele, 2007). In fact, laser bending of aluminum sheets is rarely mentioned in scientific studies in comparison with steel sheets. In 1998, Magee et al. studied the laser bending of high strengths alloys (i.e., titanium and AlCuMg aluminum alloy) but only thin sheets were considered (Magee, 1998). They concluded that the bend rate decreased with increasing irradiations over the same track due to an increase in the sample section modulus. In 2001, Ramos et al. evaluated microstructure and microhardness of Al-2024-T3 sheets which were laser bent by a carbon dioxide laser (Ramos, 2001). It is very hard to find additional information about laser bending of aluminum alloy sheets also for common alloys as well as for thick sheets. Dealing with the Al-Mg alloy AA 5005, some studies about laser processing are available in the case of welding. In 2000, Dos Santos et al. investigated electron beam and laser welded steels, superalloys, titanium and aluminum alloys (2024, 6061, 7020, and 5005) (Dos Santos, 2000). Nevertheless there is great scientific interest in this kind of aluminum alloy due to its industrial application. In 2005, Engler and An (2005) studied the correlation between texture and plastic anisotropy, and Lapovok et al. (2007) scrutinized the properties of ultrafine-grain alloy sheets by means of equal channel angular pressing. An interesting aspect of the present work is the use of aesthetic anodized aluminum sheets for laser bending; with the presence of an oxide layer on the surface which increase the aluminum laser absorption.

In the current work, authors study laser bending of AA 5005 thick sheets by means of a high power diode laser. This kind of laser source was already used to bend stainless steel and pure aluminum sheets with a lower thickness (Quadrini, 2007; Casamichele, 2007). In a further study, numerical modeling allowed to predict residual stresses during bending (Gheorghies, 2009). Very recently, numerical modeling was also used to investigate the effect that the laser beam geometries have on the process and the final product characteristics (Che Jamil, 2011). However important aspects have been excluded by the experimentation, such as the effect of the power on the absorption coefficient. In the following, these aspects are taken into account as well as the laser formability of 5005 alloy under different process conditions.