Journal of Ultrafine Grained and Nanostructured Materials

Journal of Ultrafine Grained and Nanostructured Materials

Significant grain refinement and enhanced mechanical properties of 6070 Al alloy via Ti/Sr addition and hot extrusion

Document Type : Research Paper

Authors
Masoud Emamy 1
Bita Pourbahari 2
Meysam Mostafapour 1
1 School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran.
2 Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada.
10.22059/jufgnsm.2020.02.11
Abstract
The effects of Al-5Ti-1B and Al-10Sr master alloys on the microstructure and tensile properties of extruded 6070 Al alloy have been investigated in current research. Different amounts of Al-5Ti-1B and Al-10Sr master alloys were added to provide 0.01-0.5 wt.% of each element (Ti/Sr) in the alloy before homogenization, extrusion and heat treatment process. After adding 0.03 wt.% Ti and 0.03 wt.% Sr to the alloy separately, reduction in the average grain size was found to be %83 and eutectic Si changed from needle shape to fine fibrous morphology. Although the combined addition of Al-5Ti-1B and Al-10Sr increased slightly the grain size of the alloy, there was a considerable improvement in tensile properties for the extruded and T6-heat treated specimens. Further improvement in tensile strength was achieved after T6 heat treatment for 0.1 wt% Sr + 0.03% Ti added specimens in which ultimate tensile strength (UTS) showed the highest value (410 MPa). Fracture surface examinations revealed that hot extrusion process changes the mode of fracture from brittle in the as-cast condition to a more ductile form.
Keywords
6070 Al alloy
Grain refinement
Modification
Extrusion
1. Troeger LP, Starke EA. Microstructural and mechanical characterization of a superplastic 6xxx aluminum alloy. Materials Science and Engineering: A. 2000;277(1-2):102-13.
2. Kori SA, Murty BS, Chakraborty M. Development of an efficient grain refiner for Al–7Si alloy and its modification with strontium. Materials Science and Engineering: A. 2000;283(1-2):94-104.
3. Murty BS, Kori SA, Chakraborty M. Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying. International Materials Reviews. 2002;47(1):3-29.
4. Xu C, Xiao W, Zhao W, Wang W, Shuji H, Hiroshi Y, et al. Microstructure and formation mechanism of grain-refining particles in Al-Ti-C-RE grain refiners. Journal of Rare Earths. 2015;33(5):553-60.
5. Yamauchi K, Kunimine T, Sato H, Watanabe Y. Grain Refinement of Al<sub>3</sub>Ti Dispersed Aluminum Matrix Composites by Reaction Centrifugal Mixed-Powder Method. MATERIALS TRANSACTIONS. 2015;56(1):99-107.
6. Fan Z, Wang Y, Zhang Y, Qin T, Zhou XR, Thompson GE, et al. Grain refining mechanism in the Al/Al–Ti–B system. Acta Materialia. 2015;84:292-304.
7. Wang X, Liu Z, Dai W, Han Q. On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys. Metallurgical and Materials Transactions B. 2015;46(4):1620-5.
8. Li P, Liu S, Zhang L, Liu X. Grain refinement of A356 alloy by Al–Ti–B–C master alloy and its effect on mechanical properties. Materials & Design. 2013;47:522-8.
9. Birol Y. Efficiency of binary and ternary alloys from Al–Ti–B system in grain refining aluminium foundry alloys. International Journal of Cast Metals Research. 2013;26(5):283-8.
10. Wang T, Gao T, Nie J, Li P, Liu X. Influence of carbon source on the microstructure of Al–Ti–C master alloy and its grain refining efficiency. Materials Characterization. 2013;83:13-20.
11. Li JH, Barrirero J, Engstler M, Aboulfadl H, Mücklich F, Schumacher P. Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition. Metallurgical and Materials Transactions A. 2015;46(3):1300-11.
12. Ludwig TH, Schonhovd Dæhlen E, Schaffer PL, Arnberg L. The effect of Ca and P interaction on the Al–Si eutectic in a hypoeutectic Al–Si alloy. Journal of Alloys and Compounds. 2014;586:180-90.
13. Zhang W, Liu Y, Yang J, Dang J, Xu H, Du Z. Effects of Sc content on the microstructure of As-Cast Al-7wt.% Si alloys. Materials Characterization. 2012;66:104-10.
14. Liu X, Zhang Y, Beausir B, Liu F, Esling C, Yu F, et al. Twin-controlled growth of eutectic Si in unmodified and Sr-modified Al–12.7%Si alloys investigated by SEM/EBSD. Acta Materialia. 2015;97:338-47.
15. Li JG, Zhang BQ, Wang L, Yang WY, Ma HT. Combined effect and its mechanism of Al–3wt.%Ti–4wt.%B and Al–10wt.%Sr master alloy on microstructures of Al–Si–Cu alloy. Materials Science and Engineering: A. 2002;328(1-2):169-76.
16. Lu L, Dahle AK. Effects of combined additions of Sr and AlTiB grain refiners in hypoeutectic Al–Si foundry alloys. Materials Science and Engineering: A. 2006;435-436:288-96.
17. Closset B, Gruzleski JE. Structure and properties of hypoeutectic Al-Si-Mg alloys modified with pure strontium. Metallurgical Transactions A. 1982;13(6):945-51.
18. Samuel E, Golbahar B, Samuel AM, Doty HW, Valtierra S, Samuel FH. Effect of grain refiner on the tensile and impact properties of Al–Si–Mg cast alloys. Materials & Design (1980-2015). 2014;56:468-79.
19. Panigrahi SK, Jayaganthan R, Pancholi V. Effect of plastic deformation conditions on microstructural characteristics and mechanical properties of Al 6063 alloy. Materials & Design. 2009;30(6):1894-901.
20. I. Polmear, Light Alloys, Butterworth-Heinemann, Amsterdam 2006 (4th ed.).
21. Maxwell I, Hellawell A. A simple model for grain refinement during solidification. Acta Metallurgica. 1975;23(2):229-37.
22. Mulazimoglu MH, Zaluska A, Paray F, Gruzleski JE. The effect of strontium on the Mg2Si precipitation process in 6201 aluminum alloy. Metallurgical and Materials Transactions A. 1997;28(6):1289-95.
23. Nafisi S, Ghomashchi R. Grain refining of conventional and semi-solid A356 Al–Si alloy. Journal of Materials Processing Technology. 2006;174(1-3):371-83.
24. Meng Y, Cui J, Zhao Z, Zuo Y. Effect of vanadium on the microstructures and mechanical properties of an Al–Mg–Si–Cu–Cr–Ti alloy of 6XXX series. Journal of Alloys and Compounds. 2013;573:102-11.
25. Apelian D, Cheng JJ. Al-Si Processing variables: effect on grain refinement and eutectic modification. AFS Transactions. 1986;94:797-808.
26. Farahany S, Idris MH, Ourdjini A. Effect of bismuth and strontium interaction on the microstructure development, mechanical properties and fractography of a secondary Al–Si–Cu–Fe–Zn alloy. Materials Science and Engineering: A. 2015;621:28-38.
27. Eiken J, Apel M, Liang S-M, Schmid-Fetzer R. Impact of P and Sr on solidification sequence and morphology of hypoeutectic Al–Si alloys: Combined thermodynamic computation and phase-field simulation. Acta Materialia. 2015;98:152-63.
28. Lu S-Z, Hellawell A. The mechanism of silicon modification in aluminum-silicon alloys: Impurity induced twinning. Metallurgical Transactions A. 1987;18(10):1721-33.
29. Liao C, Chen J, Li Y, Tu R, Pan C. Morphologies of Al4Sr Intermetallic Phase and Its Modification Property upon A356 Alloys. Journal of Materials Science & Technology. 2012;28(6):524-30.
30. Shivaprasad CG, Aithal K, Narendranath S, Desai V, Mukunda PG. Effect of combined grain refinement and modification on microstructure and mechanical properties of hypoeutectic, eutectic and hypereutectic Al-Si alloys. International Journal of Microstructure and Materials Properties. 2015;10(3/4):274.
31. Cáceres CH. Microstructure Design and Heat Treatment Selection for Casting Alloys Using the Quality Index. Journal of Materials Engineering and Performance. 2000;9(2):215-21.
32. Tekmen C, Ozdemir I, Cocen U, Onel K. The mechanical response of Al–Si–Mg/SiCp composite: influence of porosity. Materials Science and Engineering: A. 2003;360(1-2):365-71.
Journal of Ultrafine Grained and Nanostructured Materials
Volume 53, Issue 2
December 2020
Pages 190-203

  • Receive Date 09 September 2020
  • Revise Date 02 November 2020
  • Accept Date 06 November 2020