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Witold K. Krajewski and Paweł K. Krajewski AGH University of Science and Technology, Krakow

5 th  International Conference on Advances i n  Solidification  Processes ( ICASP -5). Shape of the in-situ ( Al,Zn )- Ti reinforcing particles and their influence on mechanical properties and structural stability of selected high- aluminium zinc cast alloys.

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Witold K. Krajewski and Paweł K. Krajewski AGH University of Science and Technology, Krakow

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  1. 5th International Conference on Advances in Solidification  Processes (ICASP-5) • Shape of the in-situ (Al,Zn)-Ti reinforcing particles and their influence on mechanical properties and structural stability of selected high-aluminium zinc cast alloys Witold K. Krajewski and Paweł K. Krajewski AGH University of Science and Technology, Krakow A. Lindsay Greer University of Cambridge, UK Salzburg, 17-21stJune 2019

  2. The Authors Team Prof.Witold K. Krajewski is Professor of Materials Science and Metallurgy, and formerDeputy Dean for Science and Head of Department of Engineering of Foundry Processes (EFP), Faculty of Foundry Engineering – AGH University of Science and Technology in Krakow. Dr. Paweł K. KrajewskicompletedPhD studiesat the EFP Department Prof. A. Lindsay Greer, Dr.h.c., isProfessor of Materials Science and Head of School of the PhysicalSciences - University of Cambridge, UK, and formerHead of Department (2006-2013) of Materials Science and Metallurgyat the University of Cambridge, UK

  3. 5th International Conference on Advances in Solidification Processes (ICASP-5) ACKNOWLEDGEMENTS • The PolishNational Science Centre (NCN) for financial support under projectNo. UMO-2017/25/B/ST8/00150 • The AGH University of Science and Technology – Department of FoundryProcesses Engineering and The University of Cambridge, UK – Department of Materials Science and Metallurgy for provision of laboratory facilities

  4. Why the work? • Production of the AlZn-basedalloys is still very small in Poland as compared to the Fe one, though Poland produces significant amount of pure zinc • Replacing some amount of Fe-based castings with the AlZn-based one is very important for environ-mental protection, because the AlZn-based alloys are called pollution-free alloys • They are also relatively cheaper as they have a low melting point, which allows saving on energy costs

  5. Stucture of Al casting production in Poland vs. World

  6. High-Zn Al castalloys • Within the range of Al products, the global production of Al-based cast alloys continues to increase. • Rather little attention has been paid to Al-Zn based alloys with high Zn content of 10–40 wt. %. Yet this group of high-zinc aluminium alloys possesses a special set of properties which allow for their usage for shape castings with good mechanical and damping properties. • However, wider implementation into practice requires improvement of their rather low ductility. This improvement can, for instance, be achieved through inoculation of the melt before pouring into foundry moulds, especially sand moulds.

  7. WorkOverview. State-of-Art • sufficient information concerning both theory and practice in the area of the Al-based and Mg-based alloys as well as MMCs; • insufficient information concerning grain-refinement of Al-Zn based alloys • ZnAl-based and AlZn-basedalloys, mainly the high-aluminium Zn and the high-zinc Al ones, are now of interest because of their good mechanical and tribological properties • investigations are now focused on two main directions, i.e. grain-refinement and using the AlZn-based alloys as matrix of the composites • need for refinement of the ' primary phase (solid solution of Zn in Al) whosedendrites solidify naturally as coarse branched The current state-of-artof the theory and practice of grain-refinement and metals-matrix-composites

  8. Overview. Innovative Concepts Innovative concepts: • using ZnTi-based MA (requires melt temperature of 500oC) • using Ti-based binary aluminides as a reinforcement of the ZnAl-matrix Industrial practice: Al basedcastalloys using Al-Ti-B and Al-Ti-C master alloys (MA) the Al-Ti-B and Al-Ti-C MA require melt temperatures of 720-750 oC the allowable melting temperatures for the Zn-Al alloys:550-600 oC

  9. Aims & Concepts Thepresentationis devoted to structuralmodification of high-aluminium zincalloys and high-zinc aluminium castalloys represented by Zn-(25-28) wt.% Al (Zn-(25-28)Al) and Al–(27-30)wt.% Zn alloy (Al-(27-30)Zn) doped with Ti, Cu and Mn, and inoculated with Ti-containing master alloys

  10. Materials & Techniques ALLOYS • Zn-25 wt.% Al cast alloy (Zn-25Al) • Zn-(25-28)wt.% Al-(1-2.5 wt.% Cu)-(1-2) wt.% Ticast alloy (Zn-(25-28)Al-(1-2.5Cu) – (1-2)Ti) • Al-20 wt.% Zn (Al-20Zn) • Al-(27-30)wt.% Zn-(2-3)wt.% Cu-(0.5-1)wt.% Mn (Al-27Zn-2Cu-1Mn) MASTER ALLOYS • Al-12.5 wt.% Ti (Al-12Ti) • Al-3 wt.% Ti-0.15 wt.% C (Al-3Ti-0.15C TiCAl; commercial) • Al-5 wt.% Ti-1 wt.% B (Al-5Ti5-1B TiBAl; commercial) • Zn-4 wt.% Ti master alloy (Zn-4Ti MA) • ZnAl-4wt.%Ti master alloy (ZnAl-4Ti MA) TECHNIQUES • LM; SEM-EBSD; EDS; TEM; DSC; TA; XRD; Damping (ULST 2000 Krautkramer); Tensile (INSTRON 3308); Wear (pin-on-disc); Image Analysis, Dimensionalchanges

  11. Sand Moulds (a) (c) (b) (d) Green sanddriedmoulds of lowsolidificationrate. Sand mould (a) and castings for tensile and pin-on-disc samples (b).Sand mould (c) and castings for structural examination (d)

  12. High-Aluminium ZincAlloys

  13. Initial & inoculated macrostructures: Zn-25Al-Ti [WK Krajewski, AL Greer, G Piwo- warski, PK. Krajewski, Grainrefinement of zinc-aluminium foundryalloys, 4thInternationalConference on Advances in Solidification Processes, 8-11th July 2014, Beaumont Estates,Old Windsor, UK] (a) and (b) surfaces of the samples; (c) and (d) crystalline fractures

  14. Crystallographicrelationships in the studied system AlZn-basedalloys – intermetallics [W.K. Krajewski and A.L. Greer, Materials Science Forum 508 (2006), pp. 281-285]

  15. EBSD Examinations • Structures of particles and matrix are similar: • Zn3Ti has L12 structure (F-lattice superstructure Pm3m) • Matrix isa’(f.c.c. – Fm3m) • Good lattice parameter match: • a(Al,Zn)3Ti = 3.957 Å aa’ = 4.043 Å • Orientation of most particles found to be the same as surrounding matrix by EBSD • A few particles do not have orientation relationship with matrix:particle engulfment or entrapment

  16. SEM-EBSD; Al-75Zn alloy refined with Zn-4Ti MA a, b – Ti(Al,Zn)3 particle c, d – surrounding matrix a b d c [Krajewski W.K. and Greer A.L., Materials Science Forum508 (2006) pp.281-286]

  17. Initial & inoculatedmicrostructures: Zn-25Al-Ti LM pictures of microstructures of the Zn-25Al alloy. (e) initial alloy; (f) alloy inoculated with Zn-Ti MA – 0.04 wt.% Ti(Leica DM IRM LM) [W.K. Krajewski, A.L. Greer, G. Piwowarski, P.K. Krajewski, Property enhancement by grain-refinement of zinc-aluminium foundry alloys, Proceedings of 4th International Conference in Advances of Solidification Processes (ICASP-4), IOP Conference Series: Materials Science and Engineering 117 (2016), paper No. 012004. DOI:10.1088/1757-899X/117/1/012004]]

  18. Reinforced structures: Zn-25Al-Ti Examplesof the master alloys with ternary aluminidesTi(Al, Zn)3: (a) coming from D022Al3Ti phase; (b) coming from L12TiZn3phase. (c) and (d): Pin-on-disc examined samples of Zn-25Al-(1.5-2) Ti composites with visible Ti(Al, Zn)3 reinforcing particles

  19. Binary Zn-25AlsandcastalloytensilestrengthUTS & A5elongation

  20. Zn-25Albasedalloys: Tribologicalcharacteristics Changes of the samples temperature and friction coefficient during thedry pin-on-disctest Samples  8 mm, load 0.8 MPa, sliding speed 0.7 m/s [KrajewskiW.K., In situ Ternary Ti Aluminide Particulate Reinforcement of High-Aluminium Zn-based MMCs. Proceedings of the 2ndInt.Conf. and Exhibition on New Developments in Metallurgical Process Technology. AssociazioneItaliana di Metallurgia. Riva del Garda, 2004]

  21. High-Zinc Aluminium Alloys

  22. High-Zinc Aluminium Alloys Composition: Al – (10-40) wt.% Zn + additions of Cu, Si, Mg, Mn Typical usesinclude shape castings and parts of increased damping and tribologicalproperties Higher Zn content increases UTS (~300 MPa) Need for refinement of primary f.c.c. -Al phase Improves mechanical properties: greater elongation higher impact strength

  23. Initial structure: Al-20Zn sand cast alloy • Coarse primary dendrites of the -Al phase • Coarse-grain macrostructure 500µm [Krajewski W.K., Greer A.L., Zych J, Buras J., Foundry Trade Journal180 (2007) No. 3642, April 2007, pp. 97-100]

  24. Initial & inoculated macrostructure: Al-20Zn sand cast alloy • Coarse grainsof the -Al phase • Refinedgrainsof the -Al phase Example of the refined Al-Zn (Al - 20 wt.% Zn) matrix after addition AlTi-based master alloy. (a) initial alloy; (b) alloy doped with the master alloy

  25. Al-20Zn sand-castalloy. Changes of structurefinenessafterinoculation b a 200 mm c AlZn20 initial alloy. (a) Etched surface of tensile sample ; (b) Cross section macrostructure ; (c) Coarse a(Al) dendrites. 200 mm a b c 500 mm AlZn20 alloy inoculated with ZnTi-based master alloy. (a) Etched surface of tensile sample ; (b) Cross section of macrostructure with visible refined a(Al) dendrites. Al-3Ti-0.15C grain refiner, Light microscopy [Krajewski, W.K., Buras, J., Krajewski, P.K., Greer, A.L., Faerber, K., Schumacher, P. New developments of Al-Zn cast alloys. In:Aluminium Two Thousand & ICEB 2015, 12 - 16 May 2015, Florence, Italy: United Aluminium World]

  26. Graindiameter vs. Tensilestrength, Elongation and Attenuationcoefficient (a) (b) (c) AlZn20 alloy. (a) Mean grain diameter ; (b) UTS - Ultimate tensile strength and A5 – Elongation ; (c) Attenuation coefficient [Krajewski, W.K., Buras, J., Krajewski, P.K., Greer, A.L., Faerber, K., Schumacher, P. New developments of Al-Zn cast alloys. In:Aluminium Two Thousand & ICEB 2015, 12 - 16 May 2015, Florence, Italy: United Aluminium World]

  27. Strengthproperties of Al-20Zn sand-castalloydoped with TiCAl MA Strength properties of the series of modified AlZn20 alloy doped with 100 ppm Ti introduced with Al-3Ti-0.15C master alloy. M-UTS and M-A5 are, accordingly, mean values of ultimate tensile strength (UTS) and elongation (A5) Strength properties of the series of non-modified AlZn20 alloy. M-UTS and M-A5 are, accordingly, mean values of ultimate tensile strength (UTS) and elongation (A5) Improvedductility with strengthpracticallypreservedorimproved [W.K. Krajewski, J. Buraś, P.K. Krajewski, G. Piwowarski, Ultrasound Wave Attenuation of GrainRefined High – Zinc AluminiumSand-castAlloys, ARCHIVES of FOUNDRY ENGINEERING 15 (2015) Issue 2, pp. 51-54]

  28. Al-Zn-Cu ternary alloys • Cu is a common addition (usually 3-5 wt.% Cu) to the Zn-Al foundry alloys. It increases strength but also leads to the formation of the metastable -CuZn4 phase which takes part in the so-called four-phase-reaction to form the stable T'-Al5Cu4Zn phase. The -CuZn4 phase is present in the structure of high-aluminiumzinc alloys and high-zincaluminium alloys for a long time after casting, while the four-phase reaction can lead to an increase of volume of the Zn-Al-Cu alloys, by as much as 4.5%. • However, reducing the Cu content degrades the tribologicalproperties of the mentionedalloys. • This problem can be solved by partial substitution of Cu with another element, e.g. Ti, Si or Mn, which also leads to the formation of a bearing phase. In the present work, Mnis used as the element partiallyreplacing Cu.

  29. Graindiameters of multicomponent Al-27 Zn basedalloy (a) (b) (c) (d) • Al-27Zn based alloys. (a) and (c) etched surface and cross-section macrostructure of Al-27Zn tensile sample; (b) and (d) etched surface and cross-section macrostructure of Al-27Zn-2.5 Cu-0.5Mn-Ti tensile sample.In:[Aluminium Two Thousand & ICEB 2017, 20- 24June 2017, Verona, Italy: United Aluminium World]

  30. Graindiameters of multicomponent Al-27Zn basedalloy 200 mm 200 mm Macrostructures of the alloys studied in the present work. Alloys 1, 3, 5 (not inoculated) have a mean grain diameter of about 450 mm. The same alloys inoculated with 100 ppm Ti in Al-3Ti-0.15C master alloy, No. 2, 4, 6, have a mean grain diameterof about 180 mm

  31. Tensilestrength & Elongation.MeanValues a . • Tensile properties of the Al-27Zn-3Cu ternary alloy vs. the Al-27Zn-2Cu-1Mn-Ti quaternary one with reduced Cu content and inoculated with addition of ~100 ppm Ti. The tensile strength (by ~22%) and elongation (by ~ 20%) of the quaternary alloy are visibly improved in comparison with the ternary one

  32. Exemplary results of the wear examinations Coefficients of mass Wm and volumeWvwear FN – load (N); SD – slidingdistance (m)

  33. Coefficients of friction Coefficient of friction of the examined alloys obtained during dry pin-on-disc measurements

  34. Dampingproperties Attenuation coefficient of the Al-27Zn-3Cu ternary alloy vs. the Al-27Zn-2Cu-1Mn-Ti quaternary one with reduced Cu content and inoculated with addition of ~100 ppm Ti. The attenuation coefficient of the quaternary alloy is visible decreased by ~ 25% in comparison with the ternary one

  35. Partialreplacement of Cu with Ti and/or Mn significantly decreases the structural instability while preserving the good tribological properties Reducing dimensional changes after partial replacing of Cu with Ti or Mn [W.K. Krajewski, A.L. Greer, P.K. Krajewski, Trends in developments of high-aluminum zinc alloys of stable structure and properties, Archives of Metallurgy and Materials 58 (2013) 845-847; W.K. Krajewski, A.L. Greer, J. Buras, G. Piwowarski, P.K. Krajewski, New developments of high-zinc Al-Zn-Cu-Mn cast alloys, Aluminium Two Thousand World Congress and International Conference on Extrusion and Benchmark ICEB, Verona, June 2017, Materials Today: Proceedings 10 (2019) 306-311

  36. Conclusion-1: GRF of Zn-25Al and Al-(20-27) Zn binaryalloys • Doping the Zn-25Al and Al-20Zn alloyswith small Ti addition increases microstructure fineness. • The observed structure refinement increases ductility of the grain refined alloysby about 30% while the alloy tensile strength remainspreservedorincreases by about 10%. • The improved ductility and basically preserved tensilestrengthare positive results of the performed grain refinement process. • Grain refinement of the Al-(20-27) Zn binaryalloysdecreases the attenuation coefficient of 1 MHz ultrasound by about 25%, but the attenuation (80–100 dB/m) remains still at the high level which is typical for high-damping alloys.

  37. Conclusion-2: GRF of Al-27Zn-Cu-Mn alloys • Grain refinement of the studied high-zinc aluminium alloys is a promising process, leading to the improvement of their tensile elongation by about 20% (from ~1.5% to ~1.8%). • Partialreplacement of Cu with Mn leads to tensile strength and wear resistance increasing by about 20% (from ~250 to ~300 MPa). • Partial replacement of Cu with Ti and/or Mn in the examined alloys leads to obtaining practically stable structure during long term natural ageing after homogenization and quenching. • The addition of Cu and Mn to binary Al-27Zn alloy allows its wear resistance to be increased, while preserving its COF • While we can obtain a material with a set of good mechanical properties, it is alsoconcluded that further studies of other property changes, e.g. creep and fatigue properties, would be desirable.

  38. Recent & Future Work • Influence of third elements (Cu, Mn, Mg, Fe) on the examinedalloysproperties • DSC examinations • SEM-EBSD examinations • Measurements of particle-size distribution • Comparison to predictions using Free-growth Model • AlZn-based MMCs reinforced with Ti aluminides

  39. 5th International Conference on Advances in Solidification Processes (ICASP-5) Thank you for your attention CONTACT Prof. Dr.-Eng. Habil. Witold K. Krajewski AGH University of Science and Technology Faculty of Foundry Engineering 23 Reymonta Street, 30-059 Krakow, POLAND email: krajwit@agh.edu.pl

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