Effect of Milling Time and Annealing on the Mechanical Response of Mechanically Milled Aluminium

Abstract:

Owing to its many exceptional properties, aluminium finds many applications in theaerospace, automotive, building and packaging industries. Enhancing its properties through alloyingor thermal treatments has been the focus of researchers’ interests for a long time. In this work, purealuminium powders were mechanically milled for up to 12 hrs and then were cold compacted andextruded to produce bulk nanostructured material. Both tensile and compressive tests wereconducted and the results compared. Post extrusion annealing treatments for up to 3 hrs wereconducted on additional samples.It was found that increasing the process control agent (PCA) content as well as the milling durationresulted in a finer microstructure and hence enhanced mechanical strength. This was accompaniedby a reduction in the ductility of the material. Moreover, compression tests revealed that thesamples are significantly more ductile in compression than in tension and that the decrease inductility with increase in milling time is less significant than in the case of tension. The differencein mechanical response is attributed to plastic instabilities. Annealing was found to enhance thetensile ductility of the samples without sacrificing strength.

• Periodical: Advanced Materials Research (Volume 445)
• Pages: 815-820
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.445.815
• Online since: January 2012
• Authors: Nesma T. Aboulkhair, Amal M. K. Esawi
• Keywords: Aluminum (Al), Annealing, Mechanical Milling, Mechanical Property

References

[1] A. S. Khan, B. Farrokh, and L. Takacs, Effect of grain refinement on mechanical properties of ball-milled bulk aluminium, Mater. Sci. and Eng. A, Vol. 489 (2008) pp.77-84.

DOI: 10.1016/j.msea.2008.01.045

[2] A. S. Khan, Y. S. Suh, X. Chen, L. Takacs, and H. Zhang, Nanocrystalline aluminium and iron: Mechanical behavior at quasi-static and high strain rates, and constitutive modeling, International Journal of Plasticity, Vol. 22 (2006) pp.195-209.

DOI: 10.1016/j.ijplas.2004.07.008

[3] H. J. Choi, S. W. Lee, J. S. Park and D. H. Bae, Tensile behavior of bulk nanocrystalline aluminium synthesized by hot extrusion of ball milled powders, Scr. Mater., Vol. 59 (2008) pp.1123-1126.

DOI: 10.1016/j.scriptamat.2008.07.030

[4] E. Ma, Recent progress in improving ductility of ultra-high strength nanostructured metals, Metals and Materials International, Vol. 10 (2004) pp.527-531.

DOI: 10.1007/bf03027414

[5] D. Jia, Y. M. Wang, K. T. Ramesh, E. Ma, Y. T. Zhu, and R. Z. Valiev, Deformation behavior and plastic instabilities of ultrafine-grained Ti, Applied Physics Letters, Vol. 79 (2001) pp.611-613.

DOI: 10.1063/1.1384000

[6] P. R. Soni, Mechanical Alloying Fundamentals and Applications, Pear Tree Press Ltd, Stevenage, 2001, England.

[7] C. Suryanarayana, Mechanical Alloying and Milling, Marcel Dekker, 2004, New York.

[8] Standard Test Method for Tension Testing of Metallic Materials, ASTM E8/E8M, American Society for Testing and Materials, (2009).

[9] E. Ma, Instabilities and ductility of nanocrystalline and ultrafine-grained metals, Scripta Materiala, Vol. 49 (2003) pp.663-668.

DOI: 10.1016/s1359-6462(03)00396-8

[10] R. Z. Valiev, I. V. Alexandrov, Y. T. Zhu, and T. C. Lowe, Paradox of strength and ductility in metals processed by severe plastic, Materials Research Society Vol. 17 (2002) pp.5-8.

DOI: 10.1557/jmr.2002.0002

[11] C. C. Koch, Optimization of strength and ductility in nanocrystalline and ultrafine grained metals, Scripta Materiala, Vol. 49 (2003) pp.657-662.

DOI: 10.1016/s1359-6462(03)00394-4

[12] B. Q. Han, E. J. Lavernia, and F. A. Mohamed, Mechanical properties of nanostructured materials, Reviews on Advanced Materials Science, Vol. 9 (2005) pp.1-16.