The aim had been to study changes in the properties of aluminium alloy AlSiMgMn. Influence of SPD of the mechanical properties had increased (Rm by 86 MPa, Ro0,2 by 175 MPa, while A had decreased to 20 %). The corrosion potentials had been evaluated in the environment of H2O and in SARS. After SPD was observed in the environment of H2O, that resistance had increased by -218 mV and after exposure up to 1 000 min there was a slight deterioration of resistance in SARS. On the surface specimens after SPD were observed higher quantities of corrosion products. After SPD was observed fatigue characteristics in torsional stress in the oblique branches Wohler curves showed favourable characteristics of about 35 %

M. Buršák

M. Halama

P. Lacková

T. Kvačkaj

English

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181 METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ, M. BURŠÁK, T. KVAČKAJ, M. HALAMAMECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082 AFTER SEVERE PLASTIC DEFORMATION (SPD)Received – Prispjelo: 2013-07-11Accepted – Prihvaćeno: 2014-05-20Preliminary Note – Prethodno priopćenjeISSN 0543-5846METABK 54(1) 181-183 (2015)UDC – UDK 669.715-539.374:620.17:620.193=111P. Lacková, M. Buršák, T. Kvačkaj, M. Halama, Faculty of Metallurgy, Technical University of Košice, SlovakiaThe aim had been to study changes in the properties of aluminium alloy AlSiMgMn. Influence of SPD of the me-chanical properties had increased (Rm by 86 MPa, Rp0,2 by 175 MPa, while A had decreased to 20 %). The corrosion potentials had been evaluated in the environment of H2O and in SARS. After SPD was observed in the environment of H2O, that resistance had increased by -218 mV and after exposure up to 1 000 min there was a slight deterioration of resistance in SARS. On the surface specimens after SPD were observed higher quantities of corrosion products. After SPD was observed fatigue characteristics in torsional stress in the oblique branches Wöhler curves showed favourable characteristics of about 35 %.Key words: aluminium alloy, severe plastic deformation, mechanical properties, corrosion properties, fatigue propertiesINTRODUCTIONIn presence the aluminium alloy AlSi1MgMn be-longing to Classes 6XXX, often used as construction material for the automotive, aerospace, shipping and construction industries. Generally, aluminium alloys are used because of their low specific weight achieves good mechanical and fatigue properties. Aluminium al-loy are having resistance in the atmospheric conditions towards to corrosion degradation with the formation of the protective oxides layer possibly hydroxides of alu-minium [1-3].At a molar ratio of Mg / Si greater than 1,73 are not susceptible to intergranular corrosion, which is caused by a small potential difference between the Mg2Si par-ticles and the matrix [4-5].Significant improvement in these properties can be achieved by combining appropriately chosen heat treat-ment followed by intensive plastic deformation through technology ECAP (Equal Channel Angular Pressing). ECAP technology lies in extruded the alloy through a die consisting of two at each perpendicular channels without changing the cross-sectional sample. Improve-ment in mechanical properties is the result of obtaining structure with ultra-fine grain size below 10 microns and precipitation hardening Mg2Si particles during ag-ing after intensive plastic deformation [6-8].The aim of the article is to assess the impact of in-tense plastic deformation on mechanical, fatigue and corrosion properties.MATERIAL AND EXPERIMENTAL METHODAs experimental material was used aluminium alloy EN AW 6082 (AlSi1MgMn) in the initial state T4 (solu-tion annealing and natural ageing) and in state after in-tensive plastic deformation prepared by ECAP for the heat treatment (solution annealing at 550 °C / 1,5 h + water quenching at room temperature + 3 x ECAP arti-ficial ageing of 100 °C / 30 h). The chemical composi-tion of the aluminium alloy is shown in Table 1.Table 1 Chemical composition of Al alloy EN AW 6082 /wt. %Al Cu Si Mg Mn Fe93,46 4,37 0,52 0,74 0,65 0,26The mechanical properties were measured by a stat-ic tensile test at room temperature on the machine ZWICK 1387, in initially state and state after ECAP are shown in Table 2.Table 2 Mechanical properties of aluminium alloyMaterialsMechanical propertiesRp0,2/ MPaRm/ MPaZ/ %A5/ %Initial state 190 298 51 22ECAPed state 365 384 39 20From the measured values of strength characteristics after intensive plastic deformation strength of yield had increased up to 92 %, ultimate strength had increased up to 28 %, while the elongation decreased down to 24 % and contraction had decreased in 10 % compared to the initial state.182   METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ et al.: MECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082Open circuit potentials (OCP) were measured by us-ing a digital multimeter Agilent 34405 DMM in a solu-tion of distilled water and SARS, whose chemical com-position are shown in Table 3. Measurement was car-ried out by two electrodes connections, which consisted working electrode (sample testing of materials) and reference saturated calomel electrode (SCE).Table 3 Chemical composition of solution SARS / mMol/lHNO3 NaCl (NH4)2SO4)0,01 1 1The corrosion characteristics of the samples were evaluated in its initial state and the state after ECAP. Mark of samples is showing Table 4.Table 4 Mark of samplesMark of samplesState EnvironmentA initial distilled waterB initial SARSCE C A P e d d i s t i l l e d  w a t e rDE C A P e d S A R SDependence of open circuit potentials ESCE after ex-posure time from 1 min to 263 520 min are graphically shown in Figure 1 showing dependence of open circuit potentials for samples A and C, Figure 2 for samples B and D.Figure 1   Dependence of OCP on the exposure time of samples in distilled waterFigure 1 is showing, that sample A has a tendency to shift the positive open circuit potential, while the sam-ples C are having steady open circuit potential from the start of exposure. In both cases, exposure took 175 680 min. There was noticed fluctuation in open circujt po-tentials, where can be expected creation of a passive film on the surface. Open circuit potential after 263 520 minutes long exposure, had decreased to the level of exposure reached at 14 400 min long exposure.Same results as we had with distilled water also oc-cured in the SARS solution Sample B at the initial state Figure 2   Dependence of OCP on the exposure time of samples in SARSFigure 3 The surface of samples after exposure (263 520 min)of exposure showed potential displacement of + 366 mV. On the other hand samples B and D showed stabi-lization of the open circuit potential after 14 400 min-utes long exposure.The surface of samples after exposure (263 520 min.) are documented on Figure 3.The surfaces of samples A and B were not signifi-cantly affected, on the other hand, samples C and D were coated with a layer of white corrosion products. According to the EDX analysis, corrosion products for samples C and D, after exposure (263 520 min long) were on the basis of sulphates and chlorides of Ca, Fe, Zn and Al. Fatigue properties of the torsional load for the alu-minium alloy EN AW 6082 were evaluated on samples from the initial state and the state after ECAP at a fre-quency of 35 Hz. Diagonal branches Wöhler depend-ence is documented on to Figure 4.Following the inclination of the oblique branch Wöhler curve, can be stated that after intensive plastic deformation was increased the fatigue resistance.The time endurance strength at the number of fa-tigue cycle’s τc104 is in the initial state 220 MPa and 260MPa in the state after ECAPed. With more than τc105 183 METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ ET AL.: MECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082cycle´s, the time endurance strength is in the initial state 180 MPa and 200 MPa in the state after ECAPed.The value ratio from between endurance strength and ultimate tensile strength (τcx/Rm) are shown in Table 5.Table 5 Fatigue characteristicsStateτc/Rm104 105Initial 0,738 0,604ECAPed 0,677 0,520From the measured values shown in Table 5 can be seen that increasing in number of cycles is the ratio en-durance strength decreasing in both states of the alu-minium alloy.It is given by parametric equation, which applies, that if there is higher ultimate tensile strength, than the ratio of the endurance strength is lower.Failure fracture the samples in both states takes the place in the direction perpendicular to the axis of the sample, where the initiation took the place from the sur-face to the interior of the material.CONCLUSIONSIn the article was analyzed influence of intensive plastic deformation on the mechanical, corrosion and fatigue properties of aluminim alloy EN AW 6082 (Al-Si1MgMn) compared to initial state alloy.-   The strength characteristics of the static tensile test after ECAP increased from initial state, the yield Figure 4 Diagonal branch of the Wöhler curvestrength by 92 %, ultimate strength by 28 %, while the elongation decreased by 24 % and contraction by 10 %.-   In the exposure of distilled water sample A shows a shift the positive open circuit potential unlike sample C which achieves stable open circuit poten-tial.-   In the solution SARS samples B and D achieved stabilization open circuit potential after exposure to 14 400 min.-   The surfaces samples A and B after exposure were not significantly affected. Samples C and D were covered with a layer corrosion products that have created effective protection against corrosion de-gradation.-   In addition to the yield strength and tensile fatigue properties also increased after intensive plastic de-formation, despite a slight reduction in plastic properties.AcknowledgementThis study was supported by the grant projects VEGA 1/0549/14.This work was realized within the frame of the Op-erational Program Research and Development: “The centre of competence for industrial research and devel-opment in the field of light metals and composites“, project code ITMS: 26220220154 and financially sup-ported by a European Regional Development Fund.REFERENCES[1]   F. Zenga, et al.: Transaction of Nonferrous Metals Society, 12 (2011), 2559-2567[2]   R. Z. Valiev, et al.: Nanostructured Materials, (2006), 33-39[3]    C. N. Panagopoilos, et al.: Tribology International, 42 (2009), 886-889[4]   E. H. Hollingsworth, et al., Corrosion of Aluminum and Aluminum Alloys, ASM International, Ohio, 1987, 583-609[5]   H. Zhan, et al.: Materials and Corrosion, 59 (2008), 670-675[6]   M. Fujda, T. Kvačkaj: Journal of Metals, Materials and Minerals, 17 (2007) 2, 23-27[7]   M. A. Rekik, et al.: Physics Procedia, 2 (2009), 1337-1342[8]   M. Fujda, T. Kvačkaj, K. Nagyová: Journal of Metals, Ma-terials and Minerals, 18 (2008) 1, 81-87Note:   The responsible translator for English language is Andrea Hor-vath, Prievidza, Slovakia

Mechanical and corrosion properties of aluminium alloy EN AW 6082 after severe plastic deformation (SPD)

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181METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ, M. BURŠÁK, T. KVAČKAJ, M. HALAMAMECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082 AFTER SEVERE PLASTIC DEFORMATION (SPD)Received – Prispjelo: 2013-07-11Accepted – Prihvaćeno: 2014-05-20Preliminary Note – Prethodno priopćenjeISSN 0543-5846METABK 54(1) 181-183 (2015)UDC – UDK 669.715-539.374:620.17:620.193=111P. Lacková, M. Buršák, T. Kvačkaj, M. Halama, Faculty of Metallurgy, Technical University of Košice, SlovakiaThe aim had been to study changes in the properties of aluminium alloy AlSiMgMn. Influence of SPD of the me-chanical properties had increased (Rm by 86 MPa, Rp0,2 by 175 MPa, while A had decreased to 20 %). The corrosion potentials had been evaluated in the environment of H2O and in SARS. After SPD was observed in the environment of H2O, that resistance had increased by -218 mV and after exposure up to 1 000 min there was a slight deterioration of resistance in SARS. On the surface specimens after SPD were observed higher quantities of corrosion products. After SPD was observed fatigue characteristics in torsional stress in the oblique branches Wöhler curves showed favourable characteristics of about 35 %.Key words: aluminium alloy, severe plastic deformation, mechanical properties, corrosion properties, fatigue propertiesINTRODUCTIONIn presence the aluminium alloy AlSi1MgMn be-longing to Classes 6XXX, often used as construction material for the automotive, aerospace, shipping and construction industries. Generally, aluminium alloys are used because of their low specific weight achieves good mechanical and fatigue properties. Aluminium al-loy are having resistance in the atmospheric conditions towards to corrosion degradation with the formation of the protective oxides layer possibly hydroxides of alu-minium [1-3].At a molar ratio of Mg / Si greater than 1,73 are not susceptible to intergranular corrosion, which is caused by a small potential difference between the Mg2Si par-ticles and the matrix [4-5].Significant improvement in these properties can be achieved by combining appropriately chosen heat treat-ment followed by intensive plastic deformation through technology ECAP (Equal Channel Angular Pressing). ECAP technology lies in extruded the alloy through a die consisting of two at each perpendicular channels without changing the cross-sectional sample. Improve-ment in mechanical properties is the result of obtaining structure with ultra-fine grain size below 10 microns and precipitation hardening Mg2Si particles during ag-ing after intensive plastic deformation [6-8].The aim of the article is to assess the impact of in-tense plastic deformation on mechanical, fatigue and corrosion properties.MATERIAL AND EXPERIMENTAL METHODAs experimental material was used aluminium alloy EN AW 6082 (AlSi1MgMn) in the initial state T4 (solu-tion annealing and natural ageing) and in state after in-tensive plastic deformation prepared by ECAP for the heat treatment (solution annealing at 550 °C / 1,5 h + water quenching at room temperature + 3 x ECAP arti-ficial ageing of 100 °C / 30 h). The chemical composi-tion of the aluminium alloy is shown in Table 1.Table 1 Chemical composition of Al alloy EN AW 6082 /wt. %Al Cu Si Mg Mn Fe93,46 4,37 0,52 0,74 0,65 0,26The mechanical properties were measured by a stat-ic tensile test at room temperature on the machine ZWICK 1387, in initially state and state after ECAP are shown in Table 2.Table 2 Mechanical properties of aluminium alloyMaterialsMechanical propertiesRp0,2/ MPaRm/ MPaZ/ %A5/ %Initial state 190 298 51 22ECAPed state 365 384 39 20From the measured values of strength characteristics after intensive plastic deformation strength of yield had increased up to 92 %, ultimate strength had increased up to 28 %, while the elongation decreased down to 24 % and contraction had decreased in 10 % compared to the initial state.182  METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ et al.: MECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082Open circuit potentials (OCP) were measured by us-ing a digital multimeter Agilent 34405 DMM in a solu-tion of distilled water and SARS, whose chemical com-position are shown in Table 3. Measurement was car-ried out by two electrodes connections, which consisted working electrode (sample testing of materials) and reference saturated calomel electrode (SCE).Table 3 Chemical composition of solution SARS / mMol/lHNO3 NaCl (NH4)2SO4)0,01 1 1The corrosion characteristics of the samples were evaluated in its initial state and the state after ECAP. Mark of samples is showing Table 4.Table 4 Mark of samplesMark of samples State EnvironmentA initial distilled waterB initial SARSC ECAPed distilled waterD ECAPed SARSDependence of open circuit potentials ESCE after ex-posure time from 1 min to 263 520 min are graphically shown in Figure 1 showing dependence of open circuit potentials for samples A and C, Figure 2 for samples B and D.Figure 1  Dependence of OCP on the exposure time of samples in distilled waterFigure 1 is showing, that sample A has a tendency to shift the positive open circuit potential, while the sam-ples C are having steady open circuit potential from the start of exposure. In both cases, exposure took 175 680 min. There was noticed fluctuation in open circujt po-tentials, where can be expected creation of a passive film on the surface. Open circuit potential after 263 520 minutes long exposure, had decreased to the level of exposure reached at 14 400 min long exposure.Same results as we had with distilled water also oc-cured in the SARS solution Sample B at the initial state Figure 2  Dependence of OCP on the exposure time of samples in SARSFigure 3 The surface of samples after exposure (263 520 min)of exposure showed potential displacement of + 366 mV. On the other hand samples B and D showed stabi-lization of the open circuit potential after 14 400 min-utes long exposure.The surface of samples after exposure (263 520 min.) are documented on Figure 3.The surfaces of samples A and B were not signifi-cantly affected, on the other hand, samples C and D were coated with a layer of white corrosion products. According to the EDX analysis, corrosion products for samples C and D, after exposure (263 520 min long) were on the basis of sulphates and chlorides of Ca, Fe, Zn and Al. Fatigue properties of the torsional load for the alu-minium alloy EN AW 6082 were evaluated on samples from the initial state and the state after ECAP at a fre-quency of 35 Hz. Diagonal branches Wöhler depend-ence is documented on to Figure 4.Following the inclination of the oblique branch Wöhler curve, can be stated that after intensive plastic deformation was increased the fatigue resistance.The time endurance strength at the number of fa-tigue cycle’s τc104 is in the initial state 220 MPa and 260MPa in the state after ECAPed. With more than τc105 183METALURGIJA 54 (2015) 1, 181-183P. LACKOVÁ ET AL.: MECHANICAL AND CORROSION PROPERTIES OF ALUMINIUM ALLOY EN AW 6082cycle´s, the time endurance strength is in the initial state 180 MPa and 200 MPa in the state after ECAPed.The value ratio from between endurance strength and ultimate tensile strength (τcx/Rm) are shown in Table 5.Table 5 Fatigue characteristicsStateτc/Rm104 105Initial 0,738 0,604ECAPed 0,677 0,520From the measured values shown in Table 5 can be seen that increasing in number of cycles is the ratio en-durance strength decreasing in both states of the alu-minium alloy.It is given by parametric equation, which applies, that if there is higher ultimate tensile strength, than the ratio of the endurance strength is lower.Failure fracture the samples in both states takes the place in the direction perpendicular to the axis of the sample, where the initiation took the place from the sur-face to the interior of the material.CONCLUSIONSIn the article was analyzed influence of intensive plastic deformation on the mechanical, corrosion and fatigue properties of aluminim alloy EN AW 6082 (Al-Si1MgMn) compared to initial state alloy.-  The strength characteristics of the static tensile test after ECAP increased from initial state, the yield Figure 4 Diagonal branch of the Wöhler curvestrength by 92 %, ultimate strength by 28 %, while the elongation decreased by 24 % and contraction by 10 %.-  In the exposure of distilled water sample A shows a shift the positive open circuit potential unlike sample C which achieves stable open circuit poten-tial.-  In the solution SARS samples B and D achieved stabilization open circuit potential after exposure to 14 400 min.-  The surfaces samples A and B after exposure were not significantly affected. Samples C and D were covered with a layer corrosion products that have created effective protection against corrosion de-gradation.-  In addition to the yield strength and tensile fatigue properties also increased after intensive plastic de-formation, despite a slight reduction in plastic properties.AcknowledgementThis study was supported by the grant projects VEGA 1/0549/14.This work was realized within the frame of the Op-erational Program Research and Development: “The centre of competence for industrial research and devel-opment in the field of light metals and composites“, project code ITMS: 26220220154 and financially sup-ported by a European Regional Development Fund.REFERENCES[1]  F. Zenga, et al.: Transaction of Nonferrous Metals Society, 12 (2011), 2559-2567[2]  R. Z. Valiev, et al.: Nanostructured Materials, (2006), 33-39[3]  C. N. Panagopoilos, et al.: Tribology International, 42 (2009), 886-889[4]  E. H. Hollingsworth, et al., Corrosion of Aluminum and Aluminum Alloys, ASM International, Ohio, 1987, 583-609[5]  H. Zhan, et al.: Materials and Corrosion, 59 (2008), 670-675[6]  M. Fujda, T. Kvačkaj: Journal of Metals, Materials and Minerals, 17 (2007) 2, 23-27[7]  M. A. Rekik, et al.: Physics Procedia, 2 (2009), 1337-1342[8]  M. Fujda, T. Kvačkaj, K. Nagyová: Journal of Metals, Ma-terials and Minerals, 18 (2008) 1, 81-87Note:  The responsible translator for English language is Andrea Hor-vath, Prievidza, Slovakia

Mechanical and corrosion properties of aluminium alloy EN AW 6082 after severe plastic deformation (SPD)

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