Equilibrium shape of isolated precipitates in the α-Mg phase

Abstract The habit plane of an isolated plate-shaped precipitate in an α -Mg matrix was calculated as a function of the stress-free transformation strain (i.e., the lattice mismatch between the precipitate and α -Mg matrix) using micromechanics. The results were categorized into 10 cases according to the habit-plane orientation, and the conditions for prismatic plate precipitation (i.e., { 0 1 1 ¯ 0 } α or { 2 1 ¯ 1 ¯ 0 } α plates), which is assumed to be the most effective type of precipitation for dispersion strengthening for a given volume fraction and number density of a precipitate, were revealed. Furthermore, it was demonstrated that the equilibrium shape of precipitates (the plate- and rod-shaped precipitates often observed in Mg-based alloys) can be explained in terms of minimization of the strain energy associated with precipitation. The obtained results are believed to be essential for attempting precipitate shape control through the optimization of the lattice parameters of the precipitates and matrix phase.

[1]  Kazuhiro Hono,et al.  Age-hardening response of Mg-0.3 at.%Ca alloys with different Zn contents , 2009 .

[2]  Kazuhiro Hono,et al.  Enhanced age hardening response by the addition of Zn in Mg–Sn alloys , 2006 .

[3]  Barry L. Mordike,et al.  Structural aspects of high performance Mg alloys design , 2002 .

[4]  Mingxing Zhang,et al.  Crystallography of Mg17Al12 precipitates in AZ91D alloy , 2003 .

[5]  Kazuhiro Hono,et al.  Enhanced age hardening in a Mg–2.4 at.% Zn alloy by trace additions of Ag and Ca , 2007 .

[6]  M. Gibson,et al.  An enhanced age hardening response in Mg–Sn based alloys containing Zn , 2006 .

[7]  Xiang Gao,et al.  Enhanced age hardening response and creep resistance of Mg-Gd alloys containing Zn , 2005 .

[8]  Yunzhi Wang,et al.  Kinetics of strain-induced morphological transformation in cubic alloys with a miscibility gap , 1993 .

[9]  J. B. Clark.  Transmission electron microscopy study of age hardening in a Mg-5 wt.% Zn alloy , 1965 .

[10]  Kazuhiro Hono,et al.  Effect of double aging and microalloying on the age hardening behavior of a Mg–Sn–Zn alloy , 2011 .

[11]  Yunzhi Wang,et al.  Predicting equilibrium shape of precipitates as function of coherency state , 2012 .

[12]  Mingxing Zhang,et al.  Morphology and crystallography of Mg24Y5 precipitate in Mg–Y alloy , 2003 .

[13]  K. Hono,et al.  Atom probe characterization of plate-like precipitates in a Mg–RE–Zn–Zr casting alloy , 2003 .

[14]  Mingxing Zhang,et al.  Edge-to-edge matching and its applications: Part II. Application to Mg–Al, Mg–Y and Mg–Mn alloys , 2005 .

[15]  Yunzhi Wang,et al.  Simulation study of precipitation in an Mg–Y–Nd alloy , 2012 .

[16]  J. Saal,et al.  Physical factors controlling the observed high-strength precipitate morphology in Mg–rare earth alloys , 2014 .

[17]  J. Nie.  Effects of precipitate shape and orientation on dispersion strengthening in magnesium alloys , 2003 .

[18]  Yunzhi Wang,et al.  A simulation study of the shape of β′ precipitates in Mg–Y and Mg–Gd alloys , 2013 .

[19]  Kazuhiro Hono,et al.  Precipitation of prismatic plates in Mg–0.3Ca alloys with In additions , 2011 .

[20]  Peter W Voorhees,et al.  THE EQUILIBRIUM SHAPE OF A MISFITTING PRECIPITATE , 1994 .

[21]  A. G. Khachaturi︠a︡n.  Theory of structural transformations in solids , 1983 .

[22]  Kazuhiro Hono,et al.  Microalloying Effect on the Precipitation Processes of Mg-Ca Alloys , 2012, Metallurgical and Materials Transactions A.

[23]  Patrick M. Kelly,et al.  Edge-to-edge matching and its applications: Part I. Application to the simple HCP/BCC system , 2005 .

[24]  S. Celotto.  TEM study of continuous precipitation in Mg–9 wt%Al–1 wt%Zn alloy , 2000 .

[25]  B. Muddle,et al.  Precipitation hardening of Mg-Ca(-Zn) alloys , 1997 .

[26]  Yunzhi Wang,et al.  Shape evolution of a precipitate during strain-induced coarsening , 1991 .

[27]  Kazuhiro Hono,et al.  Precipitation hardenable Mg―Bi―Zn alloys with prismatic plate precipitates , 2009 .

[28]  Kazuhiro Hono,et al.  TEM and 3DAP characterization of an age-hardened Mg–Ca–Zn alloy , 2005 .