Effect of secondary phase particles on postrecrystallization grain growth in reactive spray deposited 5083 Al alloys
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Effect of secondary phase particles on postrecrystallization grain growth in reactive spray deposited 5083 Al alloys S.L. Dai Second Department, Beijing Institute of Aeronautical Materials, Beijing 100095, People’s Republic of China
J-P. Delplanque Engineering Division, Colorado School of Mines, Golden CO 80401-1887
E.J. Lavernia Department of Chemical and Biochemical Engineering and Materials Science, University of California at Irvine, Irvine, CA 92697-2575 (Received 22 June 1998; accepted 11 March 1999)
Grain growth behavior in reactive spray deposited Al–Mg–Mn alloy 5083 and 5083 + Zr was quantitatively studied at 500, 530, and 560 °C. Results show that reactive spray deposited 5083 processed using N2–5% O2, in which no significant volume fraction of oxide particles was found, experienced significant grain growth when annealed at 500, 530, and 560 °C following recrystallization. On the other hand, reactive spray deposited 5083 atomized with N2–10% O2 and 5083 + Zr atomized with N2–5% O2 exhibited very slow grain growth below 530 °C and limited grain growth at 560 °C. This behavior is attributed to the retardation effect of the secondary phase particles that were formed in these alloys.
I. INTRODUCTION
Normal grain growth in metals and alloys is a diffusion-controlled process driven by a reduction in the grain boundary energy. Physically, it occurs by a growth mechanism in which large grains grow at the expense of small grains, the limiting size of which is governed by equilibrium considerations. Grain growth in metals and alloys has been studied extensively, and available literature involves both theoretical and experimental approaches. Published work, some of which is summarized in Ref. 1, showed that, under isothermal heat treatment conditions, normal grain growth follows an Arrhenius empirical equation: Dn − Dn0 ⳱ Kt
(1)
where D is the mean grain size (diameter), D0 is the initial grain size, n is the grain growth exponent, K is a temperature-dependent constant, and t is the isothermal annealing time. If it is assumed that for atomic diffusion across the grain boundary to occur an energy barrier must be overcome and that n is independent of temperature, it follows that K can be written as
冉 冊
K = K0 exp −
Qc RT
(2)
where K0 is a pre-exponential rate constant, Qc is the apparent activation energy for grain growth, R is the gas constant, and T is the temperature. 2814
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 7, Jul 1999 Downloaded: 14 Mar 2015
It is well established that second-phase particles retard grain growth through elastic attraction of the particles toward the open structure of the grain boundary. The retardation of grain growth by secondary phase particles was first theoretically investigated by Zener.2 Assuming that the grain boundary moves in a rigid way, without changing its shape, and that the particles are uniformly distributed throughout the matrix, Zener arrived at the retardation pressure, PZ ⳱ 4⁄3␥( f/r), and the par
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