Texture characterization of autogenous Nd:YAG laser welds in AA5182-O and AA6111-T4 aluminum alloys

Abstract

This article reports a study of texture characterization in Nd:YAG laser welds of AA5182-O and AA6111-T4 alloys. Electron backscattering diffraction (EBSD) in the scanning electron microscope was used to determine the texture. The determination was made as a function of thickness through the sample. The results show that the welds can develop significant texture. In particular, the columnar grains that grow from the base metal into the weld have a strong 001 texture along the direction of growth.The reduced weight and high strength-to-weight ratio of aluminum alloys make them desirable alternatives for automotive structural materials. However, some significant challenges remain in the large-scale implementation of aluminum alloys in the automotive industry. One of these pertains to the selection of joining methodologies and how these methodologies impact the mechanical properties of aluminum joints. The possibility of using laser welding is very attractive because of its speed, and a number of investigations have examined its application to aluminum alloys. [1][2][3][4][5][6][7][8] However, there are some concerns with this process. For example, aluminum alloy weld strength may decrease, with respect to the parent metal. This effect is especially pronounced with heat-treatable aluminum alloys due to the loss of the T-temper treatment. Attempts to improve aluminum weld strength therefore may involve alteration of welding process parameters and postweld heat treatment.Most published work on the weld microstructure of aluminum alloys has focused on linking the weld microstructure as observed with optical microscopy or scanning electron microscopy (SEM) to the measured mechanical properties of the weld and to the compositional changes in the weld zone. Given that texture often causes anisotropic mechanical properties, its presence in the weld zones of aluminum alloys could be quite significant. An important technique for texture characterization in metals is electron backscattered diffraction (EBSD), and Reference 9 describes both the technique and a number of its applications. While the EBSD technique has been widely used to investigate texture in aluminum alloys, it has only recently been used to investigate texture in aluminum welds. To date, these studies have focused on friction stir welds, [10,11] and no studies appear to have examined texture development in laser welds in aluminum alloys. The purpose of the present work is to characterize the textures at selected depths of autogenous Nd:YAG laser welds in AA5182-O and AA6111-T4 alloys.The materials examined in this work were AA5182-O and AA6111-T4 aluminum alloys. AA5182-O is a solid-solutionstrengthened alloy that is commonly used for automotive structural components. AA6111-T4 is a solution-treated and naturally aged alloy that is usually used for automotive body panels due to its relatively high strength and good dent resistance. Typical chemical compositions of these alloys are listed in Table I and typical tensile properties are listed in Table II.Autoge...

EBSD Investigation of the Microtexture of Weld Metal and Base Metal in Laser Welded Al–Li Alloys

“…For the weld metal, the overall texture intensity of the sample HWM and the sample TWM is 12.3% and 9.4%, exhibiting a relatively weak texture in the weld metal (see Figure 3b,d and Table 1). In general, the overall texture of the weld metal is basically decided by the orientations of the grains [25] in the columnar zone [19] and the weld metal zone having the equiaxed grains is likely to have an almost random texture, while brass, copper and S components are normally encountered in the deformation texture of fcc materials [20,26]. The present work conforms this and the brass, copper, S and Goss components are in presence in the weld metal, which suggests some similar texture components in the weld metal were formed as base metal during the laser welding.…”

“…Previous reports [19,27] have suggested that the welded joint could develop several major textures and strong texture might exist at the base metal, HAZ and columnar grain zone of the weld metal, whereas the grain orientation at equiaxed grain zone in the center of weld metal was relatively random. The present work also confirms that the original base metal structure has been eliminated and replaced by a very fine equiaxed grain structure in the weld metal.…”

“…Currently, there are increasing reports concerning the considerable deformation textures in the Al–Li based alloys, and crystallographic textures in the Al–Li alloys are quite significant to the properties via rendering them anisotropic [17,18]. Given that texture often causes anisotropic mechanical properties, its presence in the weld zones of the Al–Li alloys could be quite significant [19]. The information available on weld metal texture of 5A90 Al–Li alloys is, however, relatively scanty.…”

Effect of porosities on tensile properties of laser-welded Al-Li alloy: an experimental and modelling study

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Experimental Study on Crashworthiness of Functionally Graded Thickness Thin-Walled Tubular Structures

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