Study of the effect of aging condition on strength & hardness of 6063 t5 alloy

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  • 1. STUDY OF THE EFFECT OF AGING CONDITION ON STRENGTH AND HARDNESS OF 6063-T5 ALLOYSupervised by : Dr. G.I.P. De SilvaPresented by : E.M.A.N. Ekanayaka S.A.D.T. Dharmarathna
  • 2. INTRODUCTION Aluminium - The most abundant metal in the earth crust • 8% by weight of the earth’s solid surface Properties - Durability, light weight, good extrudability and surface finish Pure metal and the alloy used as alternatives for other metals (ferrous and non-ferrous), ceramics and wood Sri Lankan demand • Structural applications: Window and Door Frames, Partitioning, L bars, U bars 2
  • 3. ALUMEX (PVT) LTD.Project was industrially focused on “Alumex”Product: Extruded Aluminium articlesRaw material: 6063-T5 Aluminium alloy 3
  • 4. ISSUESProduction cannot meet the present increased demandRelatively high cost of products 4
  • 5. PRODUCTION PROCESS Casting Homogenizing Extrusion Age Hardening Surface Treatments 5
  • 6. REMEDYReduction of time in the Age Hardening process 6
  • 7. OBJECTIVESTo reduce the Age Hardening TimeTo reduce the Energy ConsumptionTo upgrade the Mechanical Properties 7
  • 8. LITERATURE REVIEW 8
  • 9. 6063-T5 Aluminium alloy 6063 Age Hardenable Aluminium alloy • Main alloying elements: Mg (0.2 ~ 0.6 wt%) Si (0.45 ~ 0.9 wt%) T5 - Cooled from an elevated temperature and artificially aged 9
  • 10. 6063-T5 Aluminium alloy Second Phase: Mg2Si Solid solubility of Mg2Si decreases from 1.85 wt. % at the eutectic temperature of 595 C Al-Mg2Si quasi binary system forms 10
  • 11. Age hardeningStrengthening a metal by introducing small particles of another phase which barriers dislocations motionCutting through: Bowing and By pass:When the precipitates are too When precipitates are too strongsmall to be cut and inter-particle space become large Maximum hardness is achieved if the precipitates can resist cutting by dislocations, and are too close to permit by-passing of dislocations. 11
  • 12. The Age Hardening Process Solution treatment Age hardening treatment SSSS 12
  • 13. Al-Mg2Si quasi binary system Sequence of precipitates in Al-Mg2Si GP zones – First form of precipitates (unstable) Needle Shaped with the long axis along [100] of the matrix 13
  • 14. Al-Mg2Si quasi binary system Sequence of precipitates in Al-Mg2Si β΄ phase – Developed rod shape with Hexagonal crystal structure Maximum hardness 14
  • 15. Al-Mg2Si quasi binary system Sequence of precipitates in Al-Mg2Si β phase - Equilibrium phase with FCC crystal structure Alloy is over aged – Hardness decreases 15
  • 16. Al-Mg2Si quasi binary system 16
  • 17. Closely Spaced Strong Large Increased Fine Precipitates + Precipitates = Hardness Closely spaced fine precipitates • Resist dislocation Bowing and By pass Strong large precipitates • Resist cutting by dislocations This is called a Bimodal Precipitate Structure 17
  • 18. CONCEPT Two Step Aging Process 18
  • 19. Homogeneous Nucleation of a Solute Cluster r = radius of solute cluster ΔG = free energy needed to form a spherical cluster of radius r GV = change in free energy per unit volume σ = surface free energy per unit area rc = critical radius of the cluster 19
  • 20. Gibbs-Thompson equationS = Amount of super saturation at a particular temperatureK = Temperature dependent constant ( K 1/ T )rc= Critical radius of a cluster at the relevant temperature  When T increases, rc increases 20
  • 21.  At temp. T1 clusters nucleate and grow - Size distribution: rmin – rmax When temp. is raised from T1 to T2, critical radius is raised from rc1 to rc2 If cluster radius r > rc2, the cluster will survive and continue to grow If cluster radius r < rc2, the cluster will be unstable and will dissolve. But re-nucleation may occur. This results a Bimodal Precipitate Structure with both closely spaced fine precipitates + strong large precipitates, which results better Mechanical Properties. 21
  • 22. Industrially Practiced Age Hardening Process Solution treatment Age hardening treatment Process was re-performed within the laboratory Results were used as reference values •Measured Hardness(HV) – 47.05 •Total Time (Age Hardening) – 270 min 22
  • 23. Parameters Varied During the Process Temperature (oC) T2 T1 Time (min) t1 t2 t3 t4 t5  1st step temperature - T1  Time to reach the 1st step temperature - t1  Soaking time in the 1st temperature - t2  2nd step temperature - T2  Time to reach the 2nd step temperature - t3  Soaking time in the 2nd temperature – t4 23
  • 24. LIMITATIONSFurnace Limitation • The industrially acceptable range: 150oC to 250oCEnergy ConsumptionTotal Time Consumption • Below 270 min 24
  • 25. CONSTANTS Time to reach the 1st step temperature: t1 • 60 minutes 2nd step temperature: T2 • 225oC Time to reach the 2nd step temperature: t3 • 30 minutes Temperature (oC) T2 T1 t1 t2 t3 t4 t5 Time (min) 25
  • 26. STAGE 1 - VARIABLES 1st step temperature: T1 • Altered within150oC-200oC Soaking time in the 1st temperature: t2 • Varied from 45 min- 90 min for each set of temperatures Soaking time in the 2nd temperature: t4 • Varied Combinations-15 min and 30 min Temperature (oC) T2 T1 t1 t2 t3 t4 t5 Time (min) 26
  • 27.  All Specimens were Solution Treated • At 540oC for 3 hours • To remove age hardening imposed • Dissolve all precipitates Muffle Furnace 27
  • 28.  A set of combinations among the above variables were developed Heat treatments were performed using the Super C furnace for 2 samples per combination. Super C Furnace 28
  • 29.  Hardness was tested using Vickers Hardness tester • 3 per sample 6 per combination • Average was recorded Optimum suitable parameters determined using hardness obtained Vickers Hardness Tester 29
  • 30. Aging Time and Temperature Combinations Temperature (oC) T2t4 – maintained as 15 min T1T1 – varied from 150oC to 200oC t1 t2 t3 t4 t5 Time (min) 1st step 2nd step Hardness Temperature Time Temperature Time (HV) 150oC 60 min 225oC 15 min 37.85 150oC 90 min 225oC 15 min 38.25 175oC 45 min 225oC 15 min 39.10 175oC 60 min 225oC 15 min 41.68 175oC 75 min 225oC 15 min 47.58 175oC 90 min 225oC 15 min 45.93 200oC 60 min 225oC 15 min 35.05 200oC 90 min 225oC 15 min 37.87 Hardness – Not Satisfactory 30
  • 31. 31
  • 32. Temperature (oC) T2t4 – maintained as 30 min T1T1 – varied from 150oC to 200oC t1 t2 t3 t4 t5 Time (min) 1st step 2nd step Hardness Temperature Time Temperature Time (HV) 150oC 60 min 225oC 30 min 41.47 150oC 90 min 225oC 30 min 41.25 175oC 45 min 225oC 30 min 40.92 175oC 60 min 225oC 30 min 51.68 175oC 75 min 225oC 30 min 52.05 175oC 90 min 225oC 30 min 43.78 200oC 60 min 225oC 30 min 36.42 200oC 90 min 225oC 30 min 40.62 Reference Hardness (HV) – 47.05 32
  • 33. DERIVATION 1st Step Temperature (T1) : 175oC 1st Step Soaking Time (t2) : 60 minRejections • 150oC – Low hardness in acceptable time duration • 200oC – Higher energy consumption 33
  • 34. Current Status 1st step temperature : 175oC Time to reach the 1st step temperature : 60 min Soaking time in the 1st temperature : 60 min 2nd step temperature : 225oC Time to reach the 2nd step temperature : 30 min Temperature (oC) 225 175 60 60 30 t4 30 Time (min) 34
  • 35. STAGE 2 2nd step soaking time “t4” was altered • 0 ~ 60 min – 10 min intervals Differentsets of combinations were developed Samples prepared as standard tensile test specimens 14mm 66 mm (Gauge Length) 1.72mm 150 mm Tensile Test Sample 35
  • 36.  Heat Treatment - Super C • 2 specimens per combination Hardness - Vickers Hardness Tester • 3 per sample 6 per combination • Average was recorded Tensile Strength – Tensile Testing Machine Tensometer 36
  • 37. Combinations and Results for varied “t4” Heat Treatment Hardness Tensile Strength Sample no t4 (min) 1st Step 2nd Step (HV) (N/mm2) 1 Reference _ 47.05 228.41 2 175oC - 60 min 225 oC - 0 min 0 45.08 170.27 3 175oC - 60 min 225 oC - 10 min 10 45.38 182.72 4 175oC - 60 min 225 oC - 20 min 20 46.83 199.34 5 175oC - 60 min 225 oC - 30 min 30 49.13 228.41 6 175oC - 60 min 225 oC - 40 min 40 51.10 240.86 7 175oC - 60 min 225 oC - 50 min 50 47.88 240.86 8 175oC - 60 min 225 oC - 60 min 60 45.33 232.56 37
  • 38. Graph of Hardness Vs “t4” value 57.00 52.00 51.10 49.13 47.88Hardness (HV) 47.00 47.05 46.83 45.33 45.08 45.38 42.00 37.00 32.00 0 10 20 30 40 50 60 t4 value (min) 38
  • 39. Graph of Strength Vs “t4” value 260.00 240.86 240.86 240.00 232.56Tensile Strength (N/mm2) 220.00 228.41 228.41 200.00 199.34 180.00 182.72 170.27 160.00 140.00 120.00 100.00 0 10 20 30 40 50 60 t4 value (min) 39
  • 40. Energy Comparison Theoretically • Absorbed heat energy (E) = mc E= Heat energy m = Mass of samples c = Specific Heat Capacity = Temperature Difference • Since m and c are constant • Energy Ratios = Ratio of areas under the graphs Temperature (oC) Time (min) 40
  • 41. EFFECTIVENESS – Varied “t4” Heat Treatment Total Time % Time % EnergySample no t4 (min) 1st Step 2nd Step (min) Saving Saving _ 1 Reference 270 0 0 2 175oC - 60 min 225oC- 0 min 0 180 33.33 45.59 3 175oC - 60 min 225oC- 10 min 10 190 29.63 39.96 4 175oC - 60 min 225oC- 20 min 20 200 25.93 34.33 5 175oC - 60 min 225oC- 30 min 30 210 22.22 28.71 6 175oC - 60 min 225oC- 40 min 40 220 18.52 23.08 7 175oC - 60 min 225oC- 50 min 50 230 14.81 17.45 8 175oC - 60 min 225oC- 60 min 60 240 11.11 11.82Optimum was selected considering above results 41
  • 42. Developed Process Process at Alumex 225 205Temperature (oC) Temperature (oC) 175 Time (min) Time (min) 60 60 30 40 30 90 150 30 Hardness (HV) = 51.10 Hardness (HV) = 47.05 Tensile Strength (N/mm2) = 240.86 Tensile Strength (N/mm2) = 228.41 Total Time (min) = 220 Total Time (min) = 270 42
  • 43. Microstructure Observations  Microstructure • Selected sample and reference • Viewed using Metallurgical microscope (X200) • Idea about grain size Metallurgical Microscope 43
  • 44. Microstructure ObservationAfter optimized Two Step Aging TreatmentPolishing Agent: Polycrystalline Diamond PowderEtchant: 5% HNO3 + 2% HF SolutionAfter “Alumex” Practiced Aging TreatmentPolishing Agent: Polycrystalline Diamond PowderEtchant: 5% HNO3 + 2% HF Solution 44
  • 45. PROGRESS Temperature (oC) 225 175 60 60 30 40 30 Time (min) Property / parameter Practiced Process Developed Process Hardness (HV) 47.05 51.10 Tensile Strength (N/mm2) 228.41 240.86 Total Time (min) 270 220 Time Saving (min) _ 50 % Time Saving _ 18.52 % Energy Saving _ 23.08 45
  • 46. CONCLUSION  Considering Production Rate, Production Cost and Enhanced Mechanical Properties the following Age Hardening Treatment is recommended. Temperature (oC) 225 175 60 60 30 40 30 Time (min) 46
  • 47. THANK YOU 47