Microstructural characteristics and mechanical properties of Al-2024 alloy processed via a rheocasting route

Abstract

This article reports the effects of stirring speed and T6 heat treatment on the microstructure and mechanical properties of Al-2024 alloy synthesized by a rheocasting process. There was a decrease in grain size of α-Al particles corresponding to an increase in stirring speed. By increasing the stirring speed, however, the globularity of matrix particles first increased and then declined. It was also found that the hardness, compressive strength, and compressive strain increased with the increase of stirring speed. Microstructural studies revealed the presence of nonsoluble Al₁₅(CuFeMn)₃Si₂ phase in the vicinity of CuAl₂ in the rheocast samples. The required time for the solution treatment stage was also influenced by stirring speed; the solution treatment time decreased with the increase in stirring speed. Furthermore, the rheocast samples required a longer homogenization period compared to conventionally wrought alloys. Improvements in hardness and compressive properties were observed after T6 heat treatment.

Keywords

aluminum alloys / rheocasting / microstructure / mechanical properties

References

[1] Spencer DB, Mehrabian R, Flemings MC. Rheological behavior of Sn-15 pct Pb in the crystallization range. Metall. Trans., 1972, 3(7): 1925.

[2] Guo HM, Liu XB, Yang XJ, Zhang AS, Liu Y. Microstructure evolution behavior of AlSi₉Cu₃ alloy during rheocasting. Trans. Nonferrous Met. Soc. China, 2010, 20, 815.

[3] Mirzadeh H, Niroumand B. Effects of rheocasting parameters on the microstructure of rheo-centrifuged cast Al-7.1wt%Si alloy. J. Alloys Compd., 2009, 474(1–2): 257.

[4] Falak P, Niroumand B. Rheocasting of an Al-Si alloy. Scripta Mater., 2005, 53(1): 53.

[5] Nakato H, Oka M, Itoyama S, Urata M, Kawasaki T, Hashiguchi K, Okano S. Continuous semi-solid casting process for aluminum alloy billets. Mater. Trans., 2002, 43(1): 24.

[6] Fan Z, Fang X, Ji S. Microstructure and mechanical properties of rheo-diecast (RDC) aluminium alloys. Mater. Sci. Eng. A, 2005, 412(1–2): 298.

[7] Joly PA, Mehrabian R. The rheology of a partially solid alloy. J. Mater. Sci., 1976, 11, 1393.

[8] Reisi M, Niroumand B. Effects of stirring parameters on rheocast structure of Al-7.1wt.%Si alloy. J. Alloys Compd., 2009, 470, 413.

[9] Niroumand B, Xia K. 3D study of the structure of primary crystals in a rheocast Al-Cu alloy. Mater. Sci. Eng. A, 2000, 283(1–2): 70.

[10] Fan Z. Semisolid metal processing. Int. Mater. Rev., 2002, 47(2): 49.

[11] Haga T, Kapranos P. Thixoforming of laminate made from semisolid cast strips. J. Mater. Process. Technol., 2004, 157–158, 508.

[12] Hekmat-Ardakan A, Ajersch F. Effect of conventional and rheocasting processes on microstructural characteristics of hypereutectic Al-Si-Cu-Mg alloy with variable Mg content. J. Mater. Process. Technol., 2010, 210(5): 767.

[13] Seo PK, Kim DU, Kang CG. The characteristics of grain size controlled microstructure and mechanical properties of Al-Si alloy by thixocasting and rheocasting process. J. Mater. Process. Technol., 2005, 162–163, 570.

[14] Haga T, Kapranos P. Simple rheocasting processes. J. Mater. Process. Technol., 2002, 130–131, 594.

[15] Bai ZH, Qiu F, Wu XX, Liu YY, Jiang QC. Age hardening and creep resistance of cast Al-Cu alloy modified by praseodymium. Mater. Charact., 2013, 86, 185.

[16] Dey AK, Poddar P, Singh KK, Sahoo KL. Mechanical and wear properties of rheocast and conventional gravity die cast A356 alloy. Mater. Sci. Eng. A, 2006, 435–436, 521.

[17] Curle UA. Semi-solid near-net shape rheocasting of heat treatable wrought aluminum alloys. Trans. Nonferrous Met. Soc. China, 2010, 20(9): 1719.

[18] Mahathaninwong N, Plookphol T, Wannasin J, Wisutmethangoon S. T6 heat treatment of rheocasting 7075 Al alloy. Mater Sci Eng A, 2012, 532, 91-99.

[19] Lü SL, Wu SS, Wan L, An P. Microstructure and tensile properties of wrought Al alloy 5052 produced by rheo-squeeze casting. Metall. Mater. Trans. A, 2013, 44(6): 2735.

[20] ASM International Handbook Committee. ASM Metals Handbook, Vol. 15, Casting, 1991

[21] Seidt JD, Gilat A. Plastic deformation of 2024-T351 aluminum plate over a wide range of loading conditions. Int. J. Solids Struct., 2013, 50(10): 1781.

[22] Malas JC, Venugopal S, Seshacharyulu T. Effect of microstructural complexity on the hot deformation behavior of aluminum alloy 2024. Mater. Sci. Eng. A, 2004, 368(1–2): 41.

[23] Gupta AK, Prasad BK, Pajnoo RK, Das S. Effects of T6 heat treatment on mechanical, abrasive and erosive-corrosive wear properties of eutectic Al-Si alloy. Trans. Nonferrous Met. Soc. China, 2012, 22(5): 1041.

[24] Aguilera Luna I, Mancha Molinar H, Castro Román MJ, Escobedo Bocardo JC, Herrera Trejo M. Improvement of the tensile properties of an Al-Si-Cu-Mg aluminum industrial alloy by using multi stage solution heat treatments. Mater. Sci. Eng. A, 2013, 561, 1.

[25] Birol Y. Response to artificial ageing of dendritic and globular Al-7Si-Mg alloys. J. Alloys Compd., 2009, 484(1–2): 164.

[26] Seo PK, Kang CG. The effect of raw material fabrication process on microstructural characteristics in reheating process for semi-solid forming. J. Mater. Process. Technol., 2005, 162–163, 402.

[27] Martinez RA, Flemings MC. Evolution of particle morphology in semisolid processing. Metall. Mater. Trans. A, 2005, 36(8): 2205.

[28] ASM International Handbook Committee. ASM Metals Handbook, Vol. 4, Heat Treating, 1991

[29] Zoqui EJ, Robert MH. Structural modifications in rheocast Al-Cu alloys by heat treatment and implications on mechanical properties. J. Mater. Process. Technol., 1998, 78(1–3): 198.