Influence of friction stir welding parameters on the microstructural and mechanical properties of AA 6016-T4 thin welds D.M. Rodrigues a, * , A. Loureiro a , C. Leitao a , R.M. Leal a,b , B.M. Chaparro a,c , P. Vilaça d a CEMUC, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal b ESAD.CR, Polytechnic Institute of Leiria, Caldas da Rainha, Portugal c ESTA, Polytechnic Institute of Tomar, Abrantes, Portugal d IST, Technical University of Lisbon, Lisbon, Portugal article info Article history: Received 21 July 2008 Accepted 9 September 2008 Available online xxxx Keywords: Taylor welded blanks Friction stir welding Aluminium alloys, Thin sheets abstract In present work friction stir welds produced in 1 mm thick plates of AA 6016-T4 aluminium alloy, with two different tools, were analysed and compared concerning the microstructure and mechanical proper- ties. For each tool, the welding parameters were optimized in order to achieve non-defective welds. Assuming a relation between the welding parameters and the energy input per unit of length of the weld [Seidel TU, Reynolds AP. Visualization of the material flow in AA2195 friction stir welds using a marker insert technique. Metall Mater Trans A 2001;32A:2879–84; Sato YS, Urata M, Kokawa H. Parameters con- trolling microstructure and hardness during friction stir welding of precipitation-hardenable aluminum alloy 6063. Metall Mater Trans A 2002;33(3):625–35; Lim S, Kim S, Lee CG, Kim S-J. Tensile behavior of friction-stri-welded Al 6061-T651. Metall Mater Trans A 2004;35(9):2829–35; Yang B, Yan J, Sutton MA, Reynolds AP. Banded microstructure in AA2024-T351 and AA2524-T351 aluminum friction stir welds: Part I. Metallurgical studies. Mater Sci Eng A 2004;364(1–2):55–65; Peel MJ, Steuwer A, Withers PJ, Dickerson T, Shi Q, Shercliff H. Dissimilar friction stir welds in AA5083–AA6082. Part I: process parameter effects on thermal history and weld properties. Metall Mater Trans A 2006;37:2183–193; Gerlich A, Su P, Yamamoto M, North TH. Effect of welding parameters on the strain rate and microstructure of friction stir spot welded 2024 aluminum alloy. J Mater Sci 2007;42(14):5589–601; Lombard H, Hattingh DG, Steuwer A, James MN. Optimising FSW process parameters to minimise defects and maximise fatigue life in 5083- H321 aluminum alloy. Eng Fract Mech 2008;75(3–4):341–54], the welds produced were classified as ‘‘hot” and ‘‘cold welds”. The results obtained showed that the ‘‘hot” welds, obtained with the maximum tool rotational speed and the minimum traverse speed, have improved mechanical properties relative to the ‘‘cold” welds that were in undermatch condition relative to the base material. The differences in mechanical properties between the two types of welds are explained based in TEM microstructural anal- ysis. Despite the undermatched characteristics of the ‘‘cold” welds relative to the base material, formabil- ity tests demonstrated that these welds improve the drawing performance of the welded sheets. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction In our days, friction stir welding (FSW) appears as a promisingly ecologic weld method that enables to diminish material waste and to avoid radiation and harmful gas emissions usually associated with the fusion welding processes. This welding technique makes use of a nonconsumable welding tool to generate heat, by friction between it and the faying plates, and to induce strong plastic deformation of the workpiece material promoting its complex mix- ing across the joint. Detailed description of the process can be found in the literature [8,9]. Although currently FSW can be used to join several materials such as magnesium [10,11], copper [12–14], steel [15–18], tita- nium [19,20] and MMCs [21,22], the primary research and indus- trial interest for this process was for butt and lap joining of aluminium alloys, especially the 2XXX, 6XXX and 7XXX series of heat treatable aluminium alloys, usually considered to be ‘‘unwel- dable”. Concerning the FSW of the 6XXX series of aluminium al- loys, the 6061 series was the most studied, either in similar [3,23–31] and dissimilar [32–40] welding combinations. Large ef- fort was also spent in studding the FSW of the 6082 [5,28,41– 47], 6063 [2,48–51], 6056 [52–54], 6022 [55,56], 6005 [57,58], 6013 [59] and 6016 [60] series of alloys. In most of these studies the thicknesses of the plates joined ranged from 3 to 6 mm and only few of them focused in the FSW of very thin plates, less than 2 mm thick [40,44,45,60]. 0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2008.09.016 * Corresponding author. Tel.: +351 239 790 700; fax: +351 239 790 701. E-mail address: dulce.rodrigues@dem.uc.pt (D.M. Rodrigues). Materials and Design xxx (2008) xxx–xxx Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes ARTICLE IN PRESS Please cite this article in press as: Rodrigues DM et al., Influence of friction stir welding parameters on the microstructural ..., J Mater De- sign (2008), doi:10.1016/j.matdes.2008.09.016