International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 01, January 2019, pp. 1312-1320, Article ID: IJMET_10_01_133 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=01 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed STUDY ON TENSILE STRENGTH ON ARTIFICIALLY AGED AL-MG-SI ALLOY USING TAGUCHI’S TECHNIQUE Gowri Shankar M.C Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India. Y.M Shivaprakash* Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India. Jayashree P.K Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India. Gurumurthy B.M Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India. Sathyashankara Sharma Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India. *Corresponding Author ABSTRACT Al-Mg-Si alloy is most preferred material by scientists and engineers for seeking wide range of industrial applications as its strength can be easily enhanced by cold working, grain size refining, precipitation hardening and dispersion hardening. Demand for the use of Al-Mg-Si alloy is growing rapidly because it has unique combination of properties, which make it as one of the most versatile engineering materials. In the present study, attempt has been made for systematic investigation on to know the implication of age hardening parameters like, Solutionizing Time, Aging Temperature and Ageing Time on tensile strength of Al-Mg-Si alloy using Taguchi’s Design of Experiments. A linear regression model is used to predict the response. The derived results indicate that, the aging temperature and time has imperative impact on the response whereas, solutionizing time does not have a significant effect. For a definite group of parameters, the hardness has enhanced from 154 to 210 MPa, leading to an increase in Ultimate Tensile Strength by nearly 40%. http://www.iaeme.com/IJMET/index.asp 1312 editor@iaeme.com Gowri Shankar M.C, Y.M Shivaprakash, Jayashree P.K, Gurumurthy B.M and Sathyashankara Sharma Keywords: Al-Mg-Si alloy, Design of Experiments, Ultimate Tensile Strength (UTS), Artificial aging Cite this Article: Gowri Shankar M.C, Y.M Shivaprakash, Jayashree P.K, Gurumurthy B.M and Sathyashankara Sharma, Study on Tensile Strength on Artificially Aged Al-MgSi Alloy Using Taguchi’s Technique, International Journal of Mechanical Engineering and Technology, 10(01), 2019, pp.1312–1320 http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&Type=01 1. INTRODUCTION The Age Hardening process consists of three main steps namely, Solution Treatment to bring down segregation in the alloy, quenching to enable for a supersaturated solid solution and Aging to bring about the formation of coherent precipitates that strengthen the alloy by restricting dislocation movement. The strengthening of Al-Mg-Si alloys can be brought about by the very minute secondary phase particles uniformly dispersed within the base matrix; this is achieved by right heat treatment techniques [1-10]. The existence of majority of solutes like Mg and Si in the 6000 series alloy have led to a remarkable enhancement in strength due to precipitation hardening [11-14]. Researches on precipitation sequence reveals that, the variation of the hardness versus aging temperature and time can be associated to the transformation of phase taking place in the aging treatment process. The superiority of mechanical properties by aging is due to the vacancy assisted diffusion mechanism in under aged and peak aged conditions [15-18]. The appearance of GP zones is dependent on the aging temperature, which distorts the lattice planes [19]. This distortion of the lattice planes will hinder the movement of dislocations until there exists a coherency in the lattice structure [20-22]. 2. METHODOLOGY 2.1. Casting of Specimen Commercially available Al-Mg-Si alloys are melted in a furnace at 800° C. After complete melting, an appropriate amount of degasser hexachloroethane tablets are added followed by a small amount of alkaline powder (to remove impurities forming slag). Mixing was done manually to allow the gases to escape. Figure 1: Mold prepared for pouring molten metal after casting The permanent mold made of cast iron shown in Figure 1, is preheated in a separate furnace at 600°C for 2 hr. The melt is poured into the preheated permanent mold and allowed to solidify. Table 1 depicts the nominal composition weight percentage of Al-Mg-Si matrix material. Table 1 Composition (Wt.%) OF Al-Mg-Si alloy http://www.iaeme.com/IJMET/index.asp 1313 editor@iaeme.com Study on Tensile Strength on Artificially Aged Al-Mg-Si Alloy Using Taguchi’s Technique Material Si Cu Mg Cr Al Wt % 0.60 0.20 0.99 0.25 Bal 0.15 – 0.80 0.04 Bal 0.40 – 1.20 – 0.35 (Cast) Wt% 0.40 (Std.) – 0.80 2.2. Artificial aging treatment The tensile samples are prepared as per ASTM-E10 standards shown in figure 2. These test specimens are subsequently age hardened by soaking at 550oC for 3 hr followed by sudden quenching in water medium at ambient temperature. Further the solutionized specimens are artificially aged in the furnace at 100°C, 150°C and 200°C for 5, 8 and 11hr, obtained during hardness test to get peak hardness. Figure 3 shows the heat treatment cycle for Al 6061alloy. 3. EXPERIMENTAL DESIGN AND ANALYSIS 3.1. Experimental Design Classical experimental design methodologies are cumbersome and difficult to use. Hence large number of additional experiments needs to be conducted when number of parameters is large as stated by Luo et al., [25]. In this study, the Taguchi method is useful to find optimal parameters for maximum tensile strength. In the Taguchi method, process parameters, which effect the product, can be categorized as factors like control and noise factors [23-24]. The former is helpful to choose the best stability conditions in design, whereas the later represent all factors that brings about deviation. In Taguchi method, characteristic data is acquired by the use of orthogonal arrays, and to analyze the performance measure from the data to conclude on the optimal process parameters. This approach uses a special design of orthogonal arrays to study the entire parameter space with small number of experiments only. L9 orthogonal array is used with 3 factors and 3 levels. The analysis is made using MINITAB 16 software. The sequence of steps involved in the age hardening of non-ferrous aluminum alloys consist of solutionizing, quenching and artificial aging. In the above indicated steps, major process parameters taken into account for the analysis are Solutionizing time (ts), Aging temperature (Ta) and Aging time (ta) at three levels are chosen [26]. The factors and levels of experimentation is given in Table 2. The experimental design and the average tensile strength values are depicted in Table 3. http://www.iaeme.com/IJMET/index.asp 1314 editor@iaeme.com Gowri Shankar M.C, Y.M Shivaprakash, Jayashree P.K, Gurumurthy B.M and Sathyashankara Sharma Figure 2: Sample prepared for Ultimate tensile strength test (ASTM-E10M) Figure 3: Age hardening treatment cycle for Al 6061 alloy Table 2 Factors and levels of experimentation Symbol A B C Parameters Solutionizing Ageing Ageing Time (h) Level 1 1 100 5 Level 2 2 150 8 Level 3 3 200 11 Table 3 Experimental design and average measured ultimate tensile strength values http://www.iaeme.com/IJMET/index.asp 1315 editor@iaeme.com Study on Tensile Strength on Artificially Aged Al-Mg-Si Alloy Using Taguchi’s Technique Exp . No. 1 2 3 4 5 6 7 8 9 A 1 1 1 2 2 2 3 3 3 Factor B 10 15 20 10 15 20 10 15 20 C 5 8 11 8 11 5 11 5 8 Ultimate Tensile strength 170 185 154 199 192 154 210 185 165 4. RESULTS AND DISCUSSION In the current work, experiments are conducted for identifying the influence of process parameters like ts, Ta and ta to maximize UTS. The main effect plots for UTS (larger is the superior) is shown in figure 4. From the plot it is clear that the aging time and aging temperature are the significant parameters that has highest influence on the UTS. Lower aging temperature and higher aging duration results in higher UTS value, but higher aging temperature shows lower UTS. Increase in temperature makes the aging rate also to increase because of the enhanced rate of diffusion of solid atoms into the matrix. Solutionizing time found to be least contributing process parameter to influence the UTS. This is due to the fact that in bare alloy, the effect of solutionizing time is limited only to confirm complete solubility of β-phase in α-phase [27]. Also it can be observed from the main effects plot, that solutionizing time of 2 hr, aging temperature of 100ᴼ C and aging time of 10 hr are the optimum parameter combination to obtain maximum UTS during age hardening of Al 6061 alloy as shown in figure 5. The measured UTS from experiment and the predicted values from regression equation are given in Table 4. From the ANOVA Table (Table 5) it can be noticed that the aging temperature has the highest contribution (55.74%), followed by aging time (23.94%). Since the P value of solutionizing time is grater then 0.05, which indicates that solutionizing time doesn’t have significant effect on the UTS. We take a measure of the model’s overall performance referred to as the coefficient of determination and denoted by R2. In the model, R2 is obtained equal to 95.40% for UTS values. This indicates that the age hardening process parameters explain 95.40% of variance in UTS. The normal probability plot of the residuals is shown in figure 6. The predicted values are found to be statistically similar to the actual measured values, based on the probability plot. A check on the plot in figure 6 shown that the residuals generally fall on a straight line implying that the errors are distributed normally. Table 4 clearly indicates that, the predicted value obtained from regression equation is almost same as that of experimental observation. The fit obtained from experimental UTS values and predicted values are found to be good. The % error between the experimental results and the predicted values for UTS lie within 0.06 to 4.44. In the prediction of UTS values the average absolute error for hardness is observed to be around 2.41%. ANOVA essentially involves the partitioning total variation in an experiment into components ascribable to the controlled factors and error. ANOVA applied to UTS values is done for a significance level of α = 0.05, i.e., for a confidence level of 95%. The sources with P values below 0.05 are identified to have statistically significant effect on the response. http://www.iaeme.com/IJMET/index.asp 1316 editor@iaeme.com Gowri Shankar M.C, Y.M Shivaprakash, Jayashree P.K, Gurumurthy B.M and Sathyashankara Sharma Figure 4: Main effect plot of UTS for the age hardening of Al 6061 alloy Figure 5: Surface lot of UTS vs aging time and aging Temperature Figure 6: Normal probability plot for UTS measurement. Table 4 Regression data showing measured, predicted and residual values for the UTS. http://www.iaeme.com/IJMET/index.asp 1317 editor@iaeme.com Study on Tensile Strength on Artificially Aged Al-Mg-Si Alloy Using Taguchi’s Technique Exp No. 1 2 3 4 5 6 7 8 9 Measured Predicted UTS UTS (MPa) (MPa) 170 172.71 185 185.04 154 155.37 199 200.04 192 193.61 154 156.82 210 210.41 185 186.2 165 166.53 Difference % Error 2.71 4.44 0.04 0.06 1.37 2.32 1.94 2.73 1.61 2.33 2.82 4.78 0.41 0.55 1.2 1.94 1.53 2.55 Average error = 2.41 The regression equation for UTS is, BHN= 67.0 + 2.17 * Solutionizing Time (A)-0.0967*Aging Temperature (B) + 1.06*Aging Time (C) Table 5 Analysis of variance for UTS values Source D F Seq SS Adj SS Adj MS F P %Contrib ution Rank 2 48.222 48.22 24.11 16.69 0.057 19.17 3 Solutionizing Time (A) Aging Temperature (B) Aging Time (C) 2 140.22 140.2 70.11 48.54 0.020 55.74 1 2 60.222 60.22 30.11 20.85 0.046 23.94 2 Residual Error Total 2 8 2.889 251.55 2.889 1.444 R2 95.40% 5. CONCLUSION On the basis of results of experiments, the following points are concluded• The experimental results indicate that the aging temperature has the highest influence on the UTS followed by the aging time. • Present study shows that maximum UTS is achieved at aging temperature of 100ᴼC, aging time of 10 hr and solutionizing time of 2 hr. • It is also observed that UTS decreases with increase in aging temperature due to enhanced rate of diffusion. From the experiments it is also inferred that solutionizing time has very less influence on the UTS. • The analysis of study demonstrates that there is a close match among the experimental and the predicted values of the UTS. http://www.iaeme.com/IJMET/index.asp 1318 editor@iaeme.com Gowri Shankar M.C, Y.M Shivaprakash, Jayashree P.K, Gurumurthy B.M and Sathyashankara Sharma RFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] Babakoohi Ashraf., Mohammadi H. and Habibollazade A., Evaluation of precipitation hardening heat treatment of PH 17-7 stainless steel spring. I.J. Matls. Sci. Engg., 2016, 13(2), 20-28. Chee F.T, and Mohamad R.S., Effect of Hardness Test on Precipitation Hardening Aluminium Alloy 6061-T6. Chi. Matls. J. Sci., 2009, 36(3), 276-286. Nikoogoftar, N., Razavi, S.H. and Ghanbari, M., Effect of short heat treatment routes on the tribological properties of Ti-6Al-4 alloy. Ir. J. Mat. Sci. Engg., 2017, 14(3), 21-33. Tavighi, K, Emamy, M.,Emamy A.R, Effects of Cu and solution heat treatment on the microstructure and hardness of In-Situ Aluminium matrix composite containing Al4SR phase. Ir. J. Mat. Sci. Engg., 2014, 11(4), 48-54. Gracio J.J, F. Barlat, E.F. Rauch, P.T. Jones., Artificial aging and shear deformation behaviour of 6022 aluminium alloy, I. J. Plas., 2004,20(1),427–445. Hashim J, L. Looney, M.S.J. Hashmi., Metal matrix composites: production by the stir casting method. J. Mat. Proc. Tech. 1999, 92(1), 1-7. Hashim J, Looney L, M.S.J. Hashmi., The enhancement of wettability of SiC particles in cast aluminium matrix composites. J. Mat. Proc. Tech., 2001, 119(1), 329–335. Hashim J., Looney L., M.S.J. Hashmi., The wettability of SiC particles by molten aluminium alloy. J. Mat. Proc. Tech., Vol-119:324–8. Jacobs M.H., Nucleation and growth of precipitates in aluminium alloys”, PhD thesis, University of Warwick, 1969, 58-90. John E., Gruzleski., The treatment of liquid Aluminium and Silicon Alloys. 1990,2,172-175. Majid Vaseghi., Hyoung Seop Kim., A combination of severe plastic deformation ageing phenomena in Al–Mg–Si Alloys, Mat. Des. 2004, 36, 736-740. Miao W.F., D.E. Laughlin., Precipitation hardening in aluminum alloy 6022. Scri. Mate. 1999, 40(7), 873–878. Ozturk F, A., Sisman S., Toros S., Kilic R.C., Picu., Influence of aging treatment on mechanical properties of 6061 aluminum alloy, Mat.Des. 2010, 31(1), 972–975. Rajasekaran S., N. K. Udayashankarand Jagannath Nayak., T4 and T6 Treatment of 6061 Al15vol. % SiCp Composite, I.Schol. Res. Net., 2012, 1-5. Rajan T. V., C.P. Sharma., Ashok Sharma., Heat Treatment- Principles and Techniques, East. Econ. Second Edition, 2012, 40-78. Rafiq A., Siddiqui., Hussein A., Abdullah, Khamis R., Al-Belushi., Influence of aging parameters on the mechanical properties of 6063 aluminium alloy, J. Mat. Proc. Tech. 2012, 102(2), 234-240. Siddiqui R.A., Abdul-Wahab S.A., Pervez T., Effect of aging time and aging temp., on fatigue and fracture behavior of 6063 aluminum alloy under seawater influence, Mat. Des. 2008, 29, 70–79. Sidney H Anner., Introduction to Physical metallurgy-Second edition, 1976, 2,190-194. Vijendra Singh., Heat treatment of metals, Standard publishers distributors, 2012, 3,521-535, Wang H.Q., Sun W.L., Xing Y.Q., Microstructure Analysis on 6061 Aluminum Alloy after Casting and Diffuses Annealing Process, Ph. Proc. 2013, 521-535, 68 – 75. Young S. Park., Sang B., Lee and Nack J., Microstructure and Mechanical Properties of Strip Cast Al-Mg-Si-X Alloys, Mat. Tran, 2003, 44(12), 2617-2624. Zaklina Gnjidic., Dusan Bozic., Mirjana Mitkov., The influence of SiC particles on the compressive properties of metal matrix composites, Mat. Char. 2012, 47, 129– 138. Taguchi. Introduction to quality engineering, Asian productivity orgnization, 1990, 2, 45-70. http://www.iaeme.com/IJMET/index.asp 1319 editor@iaeme.com Study on Tensile Strength on Artificially Aged Al-Mg-Si Alloy Using Taguchi’s Technique [24] [25] [26] [27] Ross P.J., Taguchi Technique for Quality Engineering, McGraw Hill, NewYork, USA, 2nd Ed.1996, 3, 65-70. Luo H., Liu J., Wang L., Zhong Q., The effect of burnishing parameters on burnishing force and surface micro hardness”, I. J. Ad. Man. Tech. 2006, 28,707-713. Irwin Miller., Freund J.E., Probability and Statistics for Engineers,Prentice Hall India Ltd., India, 2001, 2, 34-40. Mahadevan K., Raghukandan K., Senthilvelan T., Pai B.C., U.T.S. Pillai, Investigation on the influence of heat-treatment parameters on the hardness of AA6061-SiCp composite, J. Mat. Proc.Tech.2006, 171,314–318. http://www.iaeme.com/IJMET/index.asp 1320 editor@iaeme.com