Microstructural Refinement in a Commercial Aluminum Alloy Processed by ECAP Using a Die Channel Angle of 110 Degrees

Abstract:

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement. Equal channel angular pressing (ECAP) is an efficient method for modifying the microstructure by refining grain size via severe plastic deformation (SPD) in producing ultra-fine grained materials (UFG) and nanomaterials (NM). The grain sizes produced by ECAP processing are typically in the submicrometer range and this leads to high strength at ambient temperatures. ECAP is performed by pressing test samples through a die containing two channels, equal in cross-section and intersecting at a certain angle. The billet experiences simple shear deformation at the intersection, without any precipitous change in the cross-section area because the die prevents lateral expansion and therefore the billet can be pressed more than once and it can be rotated around its pressing axis during subsequent passes. After ECAP significant grain refinement occurs together with dislocation strengthening, resulting in a considerable enhancement in the strength of the alloys. A commercial AlMgSi alloy (AA6063) was investigated in this study. The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route B_C. After ECAP, samples were cut from each specimen and prepared for metallographic analysis. The microstructure of the ECAP-ed and as-received material was investigated using optical (OLYMPUS – BX60M) and SEM microscopy (TESCAN VEGA II – XMU). It was determined that for the as-received material the microstructure shows a rough appearance, with large grains of dendritic or seaweed aspect and with a secondary phase at grain boundaries (continuous casting structure). For the ECAP processed samples, the microstructure shows a finished aspect, with refined, elongated grains, also with crumbled and uniformly distributed second phase particles after a typical ECAP texture.

• Periodical: Advanced Materials Research (Volume 1114)
• Pages: 3-8
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1114.3
• Online since: July 2015
• Authors: Nicolae Şerban*, Doina Răducanu, Nicolae Ghiban, Vasile Dănuţ Cojocaru
• Keywords: Aluminium Alloy, Equal Channel Angular Pressing, Metallographic Analysis, Severe Plastic Deformation, Ultra-Fine Grained Materials

References

[1] R.Z. Valiev, T.G. Langdon, Principles of equal-channel angular pressing as a processing tool for grain refinement, Prog. Mater. Sci., 51 (2006) 881-981.

DOI: 10.1016/j.pmatsci.2006.02.003

[2] V.D. Cojocaru, D. Raducanu, N. Serban, I. Cinca, R. Saban, Mechanical behavior comparison between un-processed and ECAE processed 6063-T835 aluminum alloy, U.P.B. Sci. Bull., Series B, 72 (2010) 193-202.

[3] M. Furukawa, Y. Iwahashi, Z. Horita, M. Nemoto, T.G. Langdon, The shearing characteristics associated with equal-channel angular pressing, Mater. Sci. Eng. A, 257 (1998) 328-332.

DOI: 10.1016/s0921-5093(98)00750-3

[4] R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu, Producing bulk ultrafine-grained materials by severe plastic deformation, JOM, 58 (2006) 33-39.

DOI: 10.1007/s11837-006-0213-7

[5] N. Serban, M. Butu, Microstructural evolution of a commercial AlMgSi alloy processed by ECAP with a die channel angle of 100°, Metall. Int., 16 (2011) 36-40.

[6] M. Furukawa, Z. Horita, T. G. Langdon, Factors influencing microstructural development in equal-channel angular pressing, Metals. Mater. Int., 9 (2003) 141-149.

DOI: 10.1007/bf03027270

[7] N. Serban, V.D. Cojocaru, M. Butu, Mechanical behavior and microstructural development of 6063-T1 aluminum alloy processed by equal-channel angular pressing (ECAP): pass number influence, JOM, 64 (2012) 607-614.

DOI: 10.1007/s11837-012-0311-7

[8] N. Serban, N. Ghiban, V.D. Cojocaru, Mechanical behavior and microstructural development of 6063-T1 aluminum alloy processed by equal-channel angular pressing (ECAP): die channel angle influence, JOM, 65 (2013) 1411-1418.

DOI: 10.1007/s11837-013-0641-0

[9] N. Ghiban, N. Serban, R. Saban, V.D. Cojocaru, B. Ghiban, A. Ghiban, ECAE die design for optimum experimental tests made on an AlMgSi alloy, Annals of DAAAM for 2009 & Proceedings of the 20th International DAAAM Symposium (Vienna, Austria), 20 (2009).

DOI: 10.2507/daaam.scibook.2008.19

[10] Y. Iwahashi, Z. Horita, M. Nemoto, T.G. Langdon, An investigation of microstructural evolution during ECAP, Acta Mater., 45 (1997) 4733-4741.

DOI: 10.1016/s1359-6454(97)00100-6

[11] Y. Iwahashi, J. Wang, Z. Horita, M. Nemoto, T.G. Langdon, Principle of equal-channel angular pressing for the processing of UFG materials, Scripta Mater., 35 (1996) 143-146.

DOI: 10.1016/1359-6462(96)00107-8

[12] Y. Iwahashi, Z. Horita, M. Nemoto, T.G. Langdon, The process of grain refinement in equal-channel angular pressing, Acta Mater., 46 (1998) 3317-3331.

DOI: 10.1016/s1359-6454(97)00494-1