Engineering, Technology & Applied Science Research Vol. 8, No. 4, 2018, 3113-3115 3113 www.etasr.com Rajaa et al.: Aging Time Effects on the Mechanical Properties of Al 6061-T6 Alloy Aging Time Effects on the Mechanical Properties of Al 6061-T6 Alloy Shatha M. Rajaa Institute of Technology Baghdad, Iraq Hassan A. Abdulhadi Institute of Technology Baghdad, Iraq Khairallah S. Jabur Institute of Technology Baghdad, Iraq Ghusoon R. Mohammed Institute of Technology Baghdad, Iraq Abstract—This work investigates the influence of artificial aging and solution heat treatment on the hardness and tensile strength (mechanical properties) of Al 6061-T6 alloy. For this investigation, several aluminum 6061-T6 alloy specimens were prepared following the ASTM 176000 recommendations. The prepared specimens were heated for 1 hour at 500ºC before being water-quenched. The procedure for artificial aging was performed for 1, 2, 3, and 4 hours at 190ºC before being slowly cooled in air. Several mechanical and characterization studies were performed on the treated specimens, including an investigation on their microstructure, tensile strength, hardness, and X-ray diffraction pattern. From the results, the strength and hardness properties of the specimens were found to be generally improved, even as the best features were obtained after 2 hours of artificial aging. Keywords-heat treatment; Al alloy 6061 T6; mechanical properties I. INTRODUCTION The 6xxx group of Al alloys has received much research attention due to their great technological potential, as well as their exceptional strength enhancement following precipitation hardening. These alloys are commonly employed in the construction and automotive sector. The metastable precursors of the equilibrium phase are precipitated in a process that involves one or more complex sequences. Their chemical content, heat treatment parameters, and casting conditions greatly influence their extrudability and determine their microstructure. This implies that the properties of several aluminum alloys can be manipulated through specific heat treatment processes. The heat treatment can be executed either through solution heating (SH) or through artificial aging (AA). In the SH process, the alloy is heated to a temperature range of 400 ºC-530ºC, before water quenching at ambient temperature, while AA or simply “hardening” is performed at about 200ºC (in case of the group 6xxx of Al alloys). The temperature for age hardening usually ranges from 160°C to 200°C [1-3]. Aluminum alloys subjected to SH treatment are believed to have varying mechanical properties which account for their varying machinability. The stability and corrosion resistance of these materials can be improved by the addition of magnesium and silicon. Several mechanical properties exhibited by the 6xxx group of aluminum alloys are attributed to the type of treatment (solution, aging time and temperature) they are exposed to [4, 5]. The impact of heat treatment on the mechanical and microstructural features of alloys has been extensively studied. Authors in [1] investigated and reported the influence of precipitation hardening on the microstructural and mechanical attributes of 6xxx-group, 6061, 6063 and 6082 Al alloys. The alloys were subjected to a 12-h heating in a furnace at a temperature of 565°C before being water quenched. The heated and cooled specimens were further exposed to AA for 98h at 175°C. The microstructural and mechanical properties of the studied samples were noted to be unaffected during AA as a result of the prior precipitation strengthening process. In [6], authors investigated the effect of combining different specified cold working and precipitation hardening procedures on the tensile strength of 6061 Al alloy. The results showed that the application of a single AA process at 180°C for 4h improved the strength of the studied specimens, while a double aging process had no influence on the mechanical features of the specimens. Additionally, the pre-aging process had a counteractive effect on the subsequent precipitation process on the material. These changes in the mechanical features of the specimens were attributed to the microstructural developments due to the conflicting influence of hardening by precipitation, work softening, and strain hardening processes on the samples. Authors in [7] studied the mechanical properties of the 6061- T6 Al alloy at ambient temperature under various pre-thermal histories that represent an electron beam welding process. During the study, a fast-heating device was fabricated to deliver a controlled application of thermal loadings on the tensile samples. From the tensile tests conducted, it was observed that the yield stress decreased at RT when the optimum temperature limit was reached and when there was decrease in the heating rate. These differences in the mechanical properties were attributed to the microstructural changes that were evidenced by Transmission Electron Microscopy. Furthermore, authors in [8] studied the quench sensitivity of the mechanical properties of 6061 and 6069 Al alloys by determining the relationship between quench delay time and the mechanical properties at varying temperatures in the range of 200°C to 500°C. From the study, it was reported that the quench sensitivity of 6069-T6 was higher compared to that of 6061, and this was attributed to the differences in their composition. The study also provided more information on the quench sensitivity of the conventional 6061 alloys. In the present study, our aim is to investigate the influence of AA time on the mechanical properties of Al 6061 T6 alloy. ten rec all sev sel ma 50 bef in spe gri 80 Al on dis aci the val wh dia Engineerin www.etasr A. Specim Several spec nsile strength commendation B. Specim The chemica oy was studied C. Catego The specime veral groups a TABL Specimen cate A B C D E D. Heat Tr Solution hea lected for th aterial was in 0°C before b fore re-heating E. Micros An optical m the microstruc ecimens for inding using S 0. The sample 2O3 solution. F the specimen stilled water + id + 1mL of H F. Hardne A Vickers ha e hardness pr lues (Hv) were 1.854Hv   here p is the ameter (mm). ng, Technology r.com II. EXPER en Preparatio cimens of the test as show n of ASTM.17 Fig. 1. Ten en Characteri al content of d using an AR rization of Spe ens were cat s presented in LE I. 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Specimen’ ss Test sents the obse Test trength of the 25 tension ma MECHANICAL ry Stress (MPa) s (MPa) on % (kg/mm2) 5 nical Properties e specimens w aid of an INST s applied at a d RD) pecimens was Technology, B RESULTS on f the studied L CONTENT OF AL- ed Value Stan 60 40 30 0 120 M 010 20 0 180 M em. mination amples is pres (B) s microstructure erved hardness specimens, as achine is presen L PROPERTIES OF T A B 332 387 285 309 10 8 95 118 3114 s of Al 6061-T6 was determin TRON 1125 ten deformation ra s determined a Baghdad, Iraq Al-6061 allo -6061 (% WT.) ndard Value 0.40-0.80 Max 0.70 0.150-0.40 Max 0.150 0.80-1.20 0.04-0.350 Max 0.250 Rem. sented in Figur (C) (E) at 100x s values of th s determined u nted in Table I THE SPECIMENS C D 432 342 315 304 6 8.2 121 117 Alloy ned at nsion ate of at the . oy is re 2. he Al- using III. E 336 292 8.5 110 Fig T6 fea thr tho gav cre Mg pat un tw res sam fin on str Engineerin www.etasr E. XRD Te The XRD pa gure 3. Fi The effect of 6 Al alloy wa atures of the rough the arti ose of the base ve the best s eated by the g6Si7) which tterns (Figure iformly distrib o hours, whil sulted in a r mples compar nding agreed w e hour (Spec rengthening of ng, Technology r.com est attern of the e ig. 3. X-ray p IV. D f AA time on t as investigated examined allo ificial aging p e metal. It was strengthening magnesium a appeared cl e 3). The p buted in the le their coarse reduction in red to those with previous r cimen B) rev f the specime y & Applied Sci examined spec (A) (B) (C) (D) phases of the spec DISCUSSION the mechanica d in this repo oys were foun process (Tabl s observed tha likely due t and silicon el learly in the particles of t microstructure ening after th the mechanic after 2 hour reports [9, 10] vealed less im en compared t ience Research Raj cimens is sho imens al properties of ort. The mech nd to be imp e III) compar at time of two to the hard p lements (MgS X-ray diffr those phases e of the alloy hree and four cal features o rs (Figure 2). ]. Artificial ag mprovement o to those treate h V jaa et al.: Aging own in f 6061 hanical proved red to hours phases Si and action were y after hours of the . This ging at on the ed for two pha gen obv har attr hin the this pro har be arti stre [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Vol. 8, No. 4, 20 g Time Effects o hours likely ases. The β p nerally harder vious from Ta rdness of the ributed to the dered the disl presence of s s study are con Aluminum 6 ocess of artific rdness value o achieved thr ificial aging ti ength and hard G. Mrówka-No and heat treatm alloys”, Archiv pp. 98-107, 201 N. R. Prabhu S treatment on s composites”, B 2010 M. N. Hawas, “ AA6061-T6”, J 152, 2013 C. F. Tan, M. R aluminum alloy 3, pp. 276-286, H. Demir, S. G aluminum alloy 2009 M. Mansourine working and ag alloy”, Transac No. 9, pp. 2072 D. Maisonnette heat treatments 6061 aluminum No. 6, pp. 2718 M. Kassner, P. 6061-T6 and 6 2011, Article ID C. Ravi, C. Wo stability of Al- 14, pp. 4213-42 ] V. Massardier microstructural its thermoelectr 2924, 2000 ] M. Murayama, processes in A 1537-1548, 199 ] G. Edwards, K sequence in Al 3893-3904, 199 ] R. Ahmad, M. mechanical and the gas metal Design, Vol. 32 018, 3113-3115 on the Mechan y due to the phase in the and less duc able I that the e alloy. The precipitation location glide. maller precipi nsistent with p V. CO 6061 alloys c ial aging with f the 6061alum rough a 2-hou ime of more t dness of the ma REFER owotnik, “Influen ment on microstruc ves of Materials S 10 Swamy, C. S. Ram strength and abra Bulletin of Materi “Effect of Ageing Journal of Kerba R. Said, “Effect of y 6061-T6”, Chian 2009 Gunduz, “The eff y”, Materials & D ejad, B. Mirzak ging treatment on ctions of Nonferr 2-2079, 2012 e, M. Suery, D. 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