Growth and transformation mechanisms of 18R and 14H in Mg-Y-Zn alloys

被引：259

作者：

Zhu, Y. M. ^{[1
]}

Morton, A. J. ^{[1
,2
]}

Nie, J. F. ^{[1
]}

机构：

[1] Monash Univ, Dept Mat Engn, Clayton, Vic 3800, Australia

[2] CSIRO Proc Sci & Engn, Clayton, Vic 3168, Australia

来源：

ACTA MATERIALIA | 2012年 / 60卷 / 19期

基金：

澳大利亚研究理事会;

关键词：

Magnesium alloys; Phase transformation; Diffusional-displacive; 18R; 14H; PERIOD ORDERED STRUCTURE; FCC-BCC BOUNDARIES; PHASE-TRANSFORMATIONS; SINGLE-CRYSTALS; STACKING-FAULTS; LONG; GD; STRENGTH; HCP; COBALT;

D O I：

10.1016/j.actamat.2012.08.022

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

The growth of and transformation between 18R and 14H phases in a Mg-8Y-2Zn-0.6Zr (wt.%) alloy have been examined using conventional transmission electron microscopy and atomic resolution high-angle annular dark-field scanning transmission electron microscopy. The growth of both 18R and 14H within the alpha-Mg matrix occurs via a ledge mechanism, with the thickness of the particle increasing by the height of the ledge as it propagates. The unit height of the growth ledges or disconnections is 1.563 nm for 18R and 1.824 nm for 14H, and the displacement vector is a/3 <(1) over bar 010 >(alpha), 18R transforms in-situ to 14H during prolonged heat treatment at 500 degrees C. The 18R to 14H transformation is shown to occur most readily in regions where the 18R structure has irregularities in the building block stacking, in particular where a pair of adjacent building blocks is separated by four rather than two alpha-Mg layers. It is proposed that the diffusional-displacive 18R to 14H transformation rate is controlled by the diffusion rate of Y and Zn atoms into the segregation layers. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

引用

页码：6562 / 6572

页数：11

共 49 条

[1] On the mechanism of formation of diffusional plate-shaped transformation products [J].

Aaronson, HI ;

Furuhara, T ;

Hall, MG ;

Hirth, JP ;

Nie, JF ;

Purdy, GR ;

Reynolds, WT .

ACTA MATERIALIA, 2006, 54 (05) :1227-1232

[2] Polytypes of long-period stacking structures synchronized with chemical order in a dilute Mg-Zn-Y alloy [J].

Abe, E. ;

Ono, A. ;

Itoi, T. ;

Yamasaki, M. ;

Kawamura, Y. .

PHILOSOPHICAL MAGAZINE LETTERS, 2011, 91 (10) :690-696

[3] Long-period ordered structure in a high-strength nanocrystalline Mg-1 at% Zn-2 at% Y alloy studied by atomic-resolution Z-contrast STEM [J].

Abe, E ;

Kawamura, Y ;

Hayashi, K ;

Inoue, A .

ACTA MATERIALIA, 2002, 50 (15) :3845-3857

[4] DISLOCATION MODELS FOR SHEAR TRANSFORMATIONS [J].

ALLEN, CW ;

LIAO, KC .

PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 1982, 74 (02) :673-681

[5]

BILBY BA, 1953, PHILOS MAG, V44, P782

[6] THEORY AND EXPERIMENT OF MARTENSITIC NUCLEATION IN ZRO2 CONTAINING CERAMICS AND FERROUS-ALLOYS [J].

CHEN, IW ;

CHIAO, YH .

ACTA METALLURGICA, 1985, 33 (10) :1827-1845

[7] Novel equilibrium two phase Mg alloy with the long-period ordered structure [J].

Chino, Y ;

Mabuchi, M ;

Hagiwara, S ;

Iwasaki, H ;

Yamamoto, A ;

Tsubakino, H .

SCRIPTA MATERIALIA, 2004, 51 (07) :711-714

[8]

Christian J.W., 2002, THEORY TRANSFORMATIO

[9]

Christian W., 1994, METALL MATER TRANS A, V25, P1821

[10] The structure of long period stacking/order Mg-Zn-RE phases with extended non-stoichiometry ranges [J].

Egusa, D. ;

Abe, E. .

ACTA MATERIALIA, 2012, 60 (01) :166-178

← 1 2 3 4 5 →