Available online at www.sciencedirect.com
Microstructure, strengthening mechanisms and hot
deformation behavior of an oxide-dispersion strengthened
UFG Al6063 alloy
H. Asgharzadeha , H.S. Kimb , A. Simchic,⁎
Department of Mechanical Engineering, University of Tabriz, P.O. Box 51666-16471, Tabriz, IranDepartment of Materials Science and Engineering, Pohang University of Science and Technology, P.O. Box 790-784, Pohang, South Korea
Department of Materials Science and Engineering and Institute for Nanoscience and Nanotechnology, Sharif University of Technology,
P.O. Box 11365-9466, Tehran, Iran
An ultrafine-grained Al6063/Al2O3 (0.8vol.%, 25 nm) nanocomposite was prepared via powder
Received 4 July 2012
metallurgy route through reactive mechanical alloying and hot powder extrusion. Scanning
Received in revised form
electron microcopy, transmission electron microscopy, and back scattered electron diffraction
12 September 2012
analysis showed that the grain structure of the nanocomposite is trimodal andcomposed of
Accepted 18 October 2012
nano-size grains (1 μm) with
random orientations. Evaluation of the mechanical properties of the nanocomposite based on
the strengthening-mechanism models revealed that the yield strength of the ultrafine-grained
nanocomposite is mainly controlled by the high-angle grain boundaries rather than nanometricAluminum matrix nanocomposite
alumina particles. Hot deformation behavior of the material at different temperatures and
strain rates was studied by compression test and compared to coarse-grained Al6063 alloy. The
activation energy of the hot deformation process for the nanocomposite was determined to be
291 kJ mol− 1,which is about 64% higher than that of the coarse-grained alloy. Detailed
microstructural analysis revealed that dynamic recrystallization is responsible for the observed
deformation softening in the ultrafine-grained nanocomposite.
© 2012 Elsevier Inc. All rights reserved.
Metal matrix composites (MMCs), which combine metallic
properties (ductility and toughness) withceramic characteristics (strength and modulus) to achieve improved strength
and higher service temperature capabilities, are attractive
structural materials for automotive and aerospace applications . The performance of MMCs can further be improved
by refining the grain structure and the size of reinforcement
particles to nanometric range [2,3]. An optimum set of mechanical properties inmetal matrix nanocomposites (MMNCs) may
be obtained when fine and thermally stable ceramic particles
are uniformly dispersed in the metal matrix, for example by
⁎ Corresponding author. Tel./fax: + 98 21 6616 5262.
E-mail address: email@example.com (A. Simchi).
1044-5803/$ – see front matter © 2012 Elsevier Inc. All rights reserved.
mechanicalalloying (MA) . In this process, a mixture of metal
powders (e.g. Al, Cu and Mg) and ceramic powders (e.g. SiC,
Al2O3 and B4C) is ground to distribute ceramic particles
throughout the metal matrix while severe plastic deformation
of the metallic particles is accompanied by grain refinement.
In-situ formation of the reinforcement particles is also feasible
via chemical reactions duringthe MA course. Mechanically
driven reduction reaction of a metal powder with an oxide
powder (e.g. Al and CuO ), mechanochemical synthesis by
milling of elemental powders (e.g. Al and C ), and reaction
between a metal powder and milling atmosphere (e.g. Al with
H2 ) are examples of the in-situ synthesis of ceramic particles
within the Al matrix. Bulk materials are then produced by...