Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

Abstract

Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

Keywords

aluminum alloys / tungsten inert gas welding / heat input / aging / mechanical properties / microstructure

References

[1] Maisonnette D, Suery M, Nelias D, Chaudet P, Epicier T. Effects of heat treatments on the microstructure and mechanical properties of a 6061 aluminium alloy. Mater. Sci. Eng. A, 2011, 528(6): 2718.

[2] Halil D, Süleyman G. The effects of aging on machinability of 6061 aluminium alloy. Mater. Des., 2009, 30(5): 1480.

[3] Khan M I. Welding Science and Technology, 2008, Lucknow, New Age International, 42.

[4] Temmar M, Hadji M, Sahraoui T. Effect of postweld aging treatment on mechanical properties of tungsten inert gas welded low thickness 7075 aluminium alloy joints. Mater. Des., 2011, 32(6): 3532.

[5] Balasubramanian V, Ravisankar V, Reddy GM. Effect of pulsed current and post weld aging treatment on tensile properties of argon arc welded high strength aluminum alloy. Mater. Sci. Eng. A, 2007, 459(1–2): 19.

[6] Malarvizhi S, Balasubramanian V. Effects of welding processes and post-weld aging treatment on fatigue behavior of AA2219 aluminum alloy joints. J. Mater. Eng. Perform., 2011, 20(3): 359.

[7] Kou S. Welding Metallurgy, 2003 2nd Ed. New Jersey, John Wiley & Sons, 304.

[8] Oppenheim T, Tewfic S, Scheck T, Klee V, Lomeli S, Dahir W, Youngren P, Aizpuru N, Clark R Jr. Lee EW, Ogren J, Es-Said OS. On the correlation of mechanical and physical properties of 6061-T6 and 7249-T76 aluminum alloys. Eng. Fail. Anal., 2007, 14(1): 218.

[9] Agarwal H, Gokhale AM, Graham S, Horstemeyer MF. Void growth in 6061-aluminum alloy under triaxial stress state. Mater. Sci. Eng. A, 2003, 341(1–2): 35.

[10] Nikseresht Z, Karimzadeh F, Golozar MA, Heidarbeigy M. Effect of heat treatment on microstructure and corrosion behavior of Al6061 alloy weldment. Mater. Des., 2010, 31(5): 2643.

[11] Kupczyk J. Application of significance tests in quantitative metallographic analysis of a C-Mn-B steel. Mater. Charact., 2006, 57(3): 171.

[12] Min D, Shen J, Lai SH, Chen J. Effect of heat input on the microstructure and mechanical properties of tungsten inert gas arc butt-welded AZ61 magnesium alloy plates. Mater. Charact., 2009, 60(12): 1583.

[13] Malarvizhi S, Raghukandan K, Viswanathan N. Effect of post weld aging treatment on tensile properties of electron beam welded AA2219 aluminum alloy. Int. J. Adv. Manuf. Technol., 2008, 37(3-4): 294.

[14] Ma T, den Ouden G. Softening behaviour of Al-Zn-Mg alloys due to welding. Mater. Sci. Eng. A, 1999, 266(1–2): 198.

[15] Marlaud T, Deschamps A, Beley F, Lefebvre W, Baroux B. Evolution of precipitate microstructures during the retrogression and re-ageing heat treatment of an Al-Zn-Mg-Cu alloy. Acta Mater., 2010, 58(14): 4814.

[16] Rezaei MR, Toroghinejad MR, Ashrafizadeh F. Effects of ARB and ageing processes on mechanical properties and microstructure of 6061 aluminum alloy. J. Mater. Process. Technol., 2011, 211(6): 1184.

[17] Sluzalec A. Theory of Thermomechanical Processes in Welding, 2005, The Netherlands, Springer, 206.

[18] Aydın H, Bayram A, Durgun I. The effect of postweld heat treatment on the mechanical properties of 2024-T4 friction stir-welded joints. Mater. Des., 2010, 31(5): 2568.