110- 116 Al-Khwarizmi Engineering Journal,Vol. 12, No. 1, P.P. Shot Peening Time Effect Department of Production (Received Abstract In this study many specimen s were (15*15*3) mm according to ASTM G71 minutes using steel ball having a diameter stress which were measured using X-Ray diffraction m after peening. Electrochemical corrosion test by Tafel extrapolation method was carried out NaCl solutions (sea water) where Corrosion The obtained results show a favorable influence of SP treatment on compressive residual stresses and hardened surface layer since compressive stress was the highest Keywords: aluminum, shot peening, surface roughness, residual 1. Introduction Aluminum and its alloys are being used successfully in a wide range of applications, from Packaging to aerospace industries du good mechanical properties and low densities. In 2024 aluminum alloy copper was the main element in the alloys (Cu) gives substantial increases in strength, permits precipitation hardening, reduces corrosion resistance, ductility and weld ability.[1,2] Shot peening (SP) means bombarding a surface with spherical shot or beads, it treatment process aimed at increasing material’s fatigue strength. Intense elastic to plastic deformation in the surface layer increases material fatigue properties by strain hardening an inducing favorable compressive residual stresses [3] The number of influential parameters on the shot-peening process is large: type, size and shape of the shots, time of peening, stream velocity, air pressure on the peened element, distance from nozzle to material surface (peening distance), nozzle angle, peening intensity and surface coverage percentage. Experience showed that Khwarizmi Engineering Journal,Vol. 12, No. 1, P.P. 110- 116 (2016) Peening Time Effect on Corrosion Behaviors of Al Zuhal abd alzahra Production and Metallurgy Engineering / University of Technology E-mail: zuhalabdalzahra@yahoo.com (Received 1 February 2015; accepted 13 September 2015) s were prepared from 2024-T3 Aluminum alloy for corrosion test by the dimensions of (15*15*3) mm according to ASTM G71-31 and then subjected to shot peening process at different time (15 diameter of 2.75 mm and Rockwell Hardness of 55RC to induce compressive Ray diffraction method, surface roughness and hardness Electrochemical corrosion test by Tafel extrapolation method was carried out in where Corrosion rate calculated using Tafle equation. obtained results show a favorable influence of SP treatment on improving corrosion compressive residual stresses and hardened surface layer, the best corrosion resistance was at S since compressive stress was the highest. , shot peening, surface roughness, residual stresses, corrosion resistance Aluminum and its alloys are being used successfully in a wide range of applications, from Packaging to aerospace industries due to their good mechanical properties and low densities. In was the main element in the alloys (Cu) gives substantial increases in strength, permits precipitation hardening, reduces corrosion resistance, ductility Shot peening (SP) means bombarding a surface with spherical shot or beads, it is a surface treatment process aimed at increasing material’s fatigue strength. Intense elastic to plastic deformation in the surface layer increases material fatigue properties by strain hardening an inducing favorable compressive residual stresses [3] e number of influential parameters on the peening process is large: type, size and shape of the shots, time of peening, stream velocity, air pressure on the peened element, distance from nozzle to material surface (peening distance), ning intensity and surface coverage percentage. Experience showed that some of the parameters may be taken as constant while others must be evaluated through Experiments and numerical simulations .Shot peening is commonly conducted in a closed cabinet designed to safely confine the media and provide proper aiming of the shot blast stream [4]. The mechanism generating the compressive stresses in the surface layer is associated with the properties of treated materials. In the case of hard materials (HV�600), these stresses are generated by forces acting normal to the treated surface. The maximal tangent stresses stresses are situated underneath the surface, at the depth of (z = 0.47 * a) (Fig.1 plastic (low-hardness) materials, such as aluminum alloys (HV �300), considerable plastic strains are generated near the surface. The increase of the size of the shot counteracted by the layer( B), which in consequence produces the internal stress distribution (Fig.1 -b). The maximal value of compressive stress is registered on the surface of the worked product. Thus generated state of stress will cause the changes in the structure of the Al-Khwarizmi Engineering Journal (2016) Al Alloy 2024-T3 University of Technology orrosion test by the dimensions of at different time (15, 30, 45) induce compressive residual hardness were tested before and in an environment of 3 .5% oving corrosion resistance as induced he best corrosion resistance was at SP time of 30 minutes stresses, corrosion resistance. some of the parameters may be taken as constant while others must be evaluated through Experiments and numerical simulations .Shot peening is commonly conducted in a closed igned to safely confine the media and provide proper aiming of the shot blast stream [4]. The mechanism generating the compressive stresses in the surface layer is associated with the properties of treated materials. In the case of hard these stresses are generated by forces acting normal to the treated surface. The maximal tangent stresses ��max) due to normal stresses are situated underneath the surface, at the (Fig.1-a). In the case of hardness) materials, such as 300), considerable plastic strains are generated near the surface. The increase of the size of the shot-peened layer( A) is counteracted by the layer( B), which in sequence produces the internal stress b). The maximal value of compressive stress is registered on the surface of the worked product. Thus generated state of stress will cause the changes in the structure of the Zuhal abd alzahra Al-Khwarizmi Engineering Journal, Vol. 12, No. 1, P.P. 110- 116 (2016) 111 surface layer, depending on the type of the worked material Fig. 1 [5]. Fig.1-a the pressure effect in accordance. Fig.1-b the effect of plastic deformation with the Hertz. Fig. 1. Compressive stress generation as a result of shot-peening process [5]. Shot peening can only be reliably controlled and optimized by measuring the subsurface residual stress distributions produced. X-ray diffraction .(XRD) is the most accurate and best developed method of quantifying the residual stresses produced by surface treatments such as shot peening XRD offers a number of advantages when compared to the various mechanical methods, or the non-linear- elastic ultrasonic or magnetic methods currently available. XRD is a linear-elastic method in which the residual stress in the material is calculated from the strain measured in the crystal lattice [6]. Corrosion is a fundamental process which plays an important role in economics and safety. Apparently corrosion cannot be avoided, but its severity can be reduced to a lower magnitude. The term 'aqueous corrosion' describes the majority of the most troublesome problems encountered when metal material is in contact with sea water. Various methods have been employed to reduce corrosion. Several techniques and methods have been developed to combat corrosion efficiency are continually being sought after, as a result of exorbitant amount spent on corrosion annually [7]. The objective of the present paper is to study the corrosion properties of SP treated high- strength aluminum 2024-T3 at different penning times. 2. Experimental Work Chemical composition in weight % of 2024- T3 Aluminum alloy which was conducted by using(Thermo ARL 3460, optical Emission spectrometer) is listed in Table (1). 20 specimens from this material were prepared in the dimensions of (15*15*3) mm according to ASTM (G71-31) to Corrosion test. Table 1, Chemical analysis of the used metal AA (2024-T3. Element Wt% Real Value Standard Value Al 92.6 Rem Ti 0 0-0.15 Cr 0.05 0-0.1 Zn 0.1 0-0.25 Si 0.4 0-0.5 Fe 0.3 0-0.5 Mn 0.6 0.3-0.9 Mg 1.5 1.2-1.8 Cu 4.4 3.8-4.9 15 of These specimens were permit to Shot peening 5 specimens for each time which was carried out at (15,30,45) min using spherically ball of 2.75 mm in diameter at constant distance between the nozzle and the specimen of 10 cm. The specimen is rotating continuously during peening to ensure 100%, the ball speed is 20 m/s. The shot peening device used was (shot tum blast control model (STB – OB) machine it was found in Institute of Technology Fig(2) , preparing specimens were classified into four series, three of them corresponded to appropriate shot time as shown in Table (2) Zuhal abd alzahra Al Fig. 2. Shot Peening Device with shot balls Table 2, Classification of corrosion test specimens. Residual stress were measured for all specimens in Table (2) by using Lab XRD Shimadzu X-ray Diffracto meter, the residual stress results are shown in Table(3) and Fig.(3) gives the relation between 2 Theta (deg ) which presented strain in brag law compressive residual stress in Sin2^Psi( Deg.) presents the specimen location and its incline with the axis. Specimen (A) Symbol conditions A As received B Shot peening for 15 minute C Shot peening for 30 minute D Shot peening for 45 minute 2 T h et a ( D eg .) Sin2^Psi( Deg.) Y=M*X+A Al-Khwarizmi Engineering Journal, Vol. 12, No. 112 Shot Peening Device with shot balls. Classification of corrosion test specimens. Residual stress were measured for all Lab XRD-6000 meter, the residual stress results are shown in Table(3) and Fig.(3) gives the relation between 2 Theta (deg ) which presented strain in brag law to calculate Mpa ,while resents the specimen location Specimen (B) Specimen (C) Specimen (D) Fig. 3. photo graph of residual Shot peening for 15 minute Shot peening for 30 minute Shot peening for 45 minute Y=M*X+A 2 T he ta ( D eg .) 2 T he ta ( D eg .) Y=M*X+A Y=M*X+A 2 T he ta ( D eg .) 2 T h et a ( D eg .) 2 T h et a ( D eg .) 2 T h et a ( D eg .) , No. 1, P.P. 110- 116 (2016) Specimen (B) Specimen (C) Specimen (D) photo graph of residual stress. Y=M*X+A Y=M*X+A Sin2^Psi( Deg.) Sin2^Psi( Deg.) Sin2^Psi( Deg.) Sin2^Psi( Deg.) Zuhal abd alzahra Al-Khwarizmi Engineering Journal, Vol. 12, No. 1, P.P. 110- 116 (2016) 113 Surface Roughness The average value of the free surface roughness was measured using (Perth meter) Type (S6P) at the surface area of specimens( A) and peened area for specimens (B,C,D ) it is indicated by the parameter (Ra) which is the center-line average of adjacent peaks, the macro hardness by using Hardness Tester Waghtech international did vary depending on which peening treatment was used. Results are shown in table(3) Table (3) The result of Rockwell B hardness, surface roughness and compressive residual stress. Symbol HRB Kg/mm2 Surface Roughness Ra (µm) Residual stress Mpa A 76 0.016 -18 B 92 1.89 -162 C 120 2.2 -266 D 128 2.32 -206 (-) symbol referred to compressive stress and it has no effect on value Corrosion Test Cell current readings were taken during a short, slow sweep of the potential. The sweep was taken from (-100 to + 100) mV relative to (OCP). Scan rate defines the speed of the potential sweep in mV/sec and its taken (10 mv). In this range the current density versus voltage curve is almost nearly linear. The tests were performed by using a WENKING Mlab multi channels potentiostat and SCI-Mlab corrosion measuring system from Bank Electroniks-Intelligent control GmbH, Germany 2007, as shown in Fig.(4) In this test, aluminum alloy (2024-T3) shot peened and un shot samples were used as working electrode (WE), a saturated calomel electrode immersed in the salt solution was used as reference Electrochemical corrosion test by Tafel extrapolation method was carried out on all samples of all time (15,30,45)min shot peening in sodium chloride solution of 3.5% NaCl with Ph of 6.8 to determine corrosion Parameters, such as corrosion potential (Ecorr) and corrosion current ( Icorr) at each time . These parameters will leads to calculate the corrosion rate according to the equation below [9]. C.R (m.p.y) = 0.13 * Icorr * eq.wt / ρ (1) Where m.p.y= mille-inches per year Icorr=corrosion current density (µΑ/cm2) Eq .wt =equivalent weight of the corroding species, ρ= density of the corroding specimens, (g/cm3). Fig. 4. The electrochemical corrosion unit. The values for the corrosion potentials and corrosion current densities were estimated from the intersection of the anodic and cathode Tafel lines. The corresponding corrosion potentials (Ecorr), corrosion current density (icorr), anodic listed in Table 4.and Fig .(5) Table 4, Corrosion result for all specimens. symbol Icorr [µA/cm2] Ecorr [mV] Corr. rate (M.p.y) A 50.57 -707 21.751 B 33 -750.2 14.19 C 7.2 -648.1 3.096 D 11.7 -617.9 4.803 Corrosion Rate=0.43 icorr Fig. 5. Electrochemical behavior polarization for all specimens. Zuhal abd alzahra Al-Khwarizmi Engineering Journal, Vol. 12, No. 1, P.P. 110- 116 (2016) 114 Sample (A) Sample (B) Sample (C) Sample (D) Fig. 6. corrosion photos. 3. Discussion From chemical composition , in table (1) it is clear that copper is the controlling main element with percentage 4% , this was giving alloys good electrical conductively but poor corrosion resistance, it is often clad with aluminum or Al-Zn for protection [10] because of copper made for lower the hydrogen over voltage values since the hydrogen over voltage for copper and intermetallic compound is much lower than for aluminum in this case to the final corrosion potential is less noble than the initial value this might indicate that the material changed from the passive to the active state in furthermore This alloy shows much more general corrosion because copper waked the protective properties and anodizing use to improve the surface oxide stability when oxygen present in the aggressive medium is negligible [8, 11]. (Table 3). Show average surface roughness of base material (USP) sample (A) was 0.016 µm. It was found to be less as compared with the shot peened samples (B,C,D) Shot peened contributed in increasing surface roughness which remaining hardness and compressive residuals stress to improvement mechanical properties and the shot time have more effect on its when increasing and this inagreament with Nashwa [12] which study the effect of shot peening time with steel balls on mechanical properties of AA2024-T4 alloyResults showed an increase in yield and tensile strength values with increasing peening time up to 15 minutes Table (4) shows corrosion results & Fig.( 5 ) the polarization curves of the all specimen which classified in Table(2),corrosion potential depends on the electrochemical behaviour of the microstructure and this is directly dependent on the quantity of the present phases for example in Fig.(5) specimen (A) has a corrosion potential of - 0.707V and a corrosion current of 50.57 µA/cm2 and the corrosion rate is 21.751 m.p.y and as the shot peen 15 min there is a decreasing in corrosion rate in small values, this is because of the comparative residual stress which formed by shot peened process cases in reduce the corrosion properties. Specimen (B) Fig .(5 )shows that for specimens C ,D as increasing in time of shots there is a decreasing in Icor value and then corrosion rate . Corrosion rate in specimen C, D is lower than it in specimen (A) inducing favorable compressive residual stresses layer which was increasing in depth with increasing in shot time this is because this layer act as oxide film productive in aluminum and its alloys when aluminum react with dissolve oxygen to form it this is Partial Matches with Khaira Salman [13] , she studied the effects of shot peening time on corrosion behaviors of AA 6061-T6 in aqueous solutions results shows a favorable influence of shot peening (SP ) treatment on corrosion resistance as induced compressive residual stresses lead to increase hardening of layer surface and decreasing in corrosion rate also Ali[14] studied the effect of shot peening time on the mechanical Corrosion spots Zuhal abd alzahra Al-Khwarizmi Engineering Journal, Vol. 12, No. 1, P.P. 110- 116 (2016) 115 Properties for two alumin um alloys AA2017- T4 and AA6063-T5The results showed that the percent elongation are increased to maximum value at 9 minute for AA 2017-T4while the minimum value was at the same time for AA 6063-T5. Fig. (6) shows the corrosion photos which insist the result above. 4. Conclusion 1. Shot peening with variable time contributed in decreasing corrosion rate. 2. The shot peening improves corrosion resistance of the Al- Alloy 2024-T3 due to the homogenous cold worked surface layer and the compressive residual stresses produced during shot peening 3. Aluminum alloys 2024-T3 has high corrosion rate because of the alloy elements such as copper. 4. The best shot time which contributed in improvement in corrosion rate is 30 min. 5. References [1] Benachour M., Hadjoui A., Benguediab M., "Heat Treatment Effect On Fatigue Crack Growth", 3rd International Conference on Integrity, Reliability and Failure, Portugal, 20-24 July 2009 . [2] Mustafa Kemal Kulekci,” Experimental Comparison of MIG and Friction Stir Welding Processes for EN AW-6061-T6 (Al Mg1 Si Cu) Aluminum Alloy”, The Arabian Journal for Science and Engineering, 35, 2006, pp.321-330. [3] Uroš Zupanc1, Janez Grum2,”Surface Integrity of Shot Peened Aluminum Alloy 7075- T651”,Strojniški vestnik - Journal of Mechanical Engineering 57,5(2011), pp.379- 384 [4] Roko Markovina, Branko Blagojević ario Ban,” Investigation of influential parameters on shot-peening of aluminum alloys Trends in the Development of Machinery and Associated Technology”, Istanbul, Turkey, 26-30 August, 2008 [5] A. fedoryszyn, p. zyzak,” Characteristics of the outer surface layer in casts subjected to shot blasting treatment Archive of Metallurgy and Materials “, Vo.55 issue 3 year 2010 pp814-818 [6] Paul S. prevéy,” X-ray diffraction characterization of residual stresses produced by Shot peening Theory and Application”, series ed. A. Niku-Lari, IITT-International, Gournay-Sur-Marne, France, 1990, pp. 81-93 [7] W. B. Wan Nik1, O. Sulaiman , “Corrosion behavior of aluminum alloy in seawater” The International Conference on Marine Technology 11-12 December 2010, BUET, Dhaka, Bangla [8] Metals Handbook, Vol.2 - Properties and Selection: Nonferrous Alloys and Special- Purpose Materials, ASM International 10th Ed. 1990. [9] Annual Book of ASTMSTANDARDS, Standard Practice for Calculation of Corrosion Rates and Related Information, G102-89,Vol. 03.02, 2004. [10] Aluminum Information at aircraftspruce.com accessed August 15, 2011. [11] R.A. Higgins ,”Engineering metallurgy part 1 “, Applied Physical metallurgy 4th Edition universities press LTD (p340 – 353)1975. [12] Nashwa Abdul –Hammied Saad” effect of shot peening time on mechanical properties of aluminum alloy aa2024 –t4” The Iraqi Journal For Mechanical And Material Engineering, Vol.14, No1, 2014. [13] Kharia Salman Hassan, Abbas Sheyaa Alwan, Sawsan Abdulshaheed Abbas,” Corrosion Behavior of Al alloys 6061-T6 Shot Peening in Different Aqueous Solution”, International Journal of Engineering and Innovative Technology (IJEIT), Volume 4, Issue 8, February 2015. [14] Ali A.Ali1, Esam A.Ebrahim2 “effect of shot peening time on mechanical properties of aluminum alloys aa2017-t4 and aa6063- t5” Diyala Journal of Engineering SciencesVol. 06, No. 02, pp. 1- 8, June 2013. �� 1، ا���د�12 �� ا���ارز�� ا������� ا�� ��ز ��� زھ�ة �� ،116 -110 )2016( T3-2024/.-�� ز�, ا�+*ف ��) ���ك ا�&%$ �#��"� ا!�����م ز ��� ا�0ھ�ة ��ج وا����دن ��� � ا�*�(� ا��)#'�'&%/ ھ#"! ا� zuhalabdalzahra@yahoo.com : ا�/�,و�. ا�-,+" ا��1�� (@�000000 و00000005? 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