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Title: Characterization of strengthening precipitate phases in a Mg-Y-Nd alloy

Abstract

Strengthening precipitate phases in a Mg-Y-Nd based alloy (WE54), aged at 250 C, have been characterized using transmission electron microscopy. Precipitation at 250 C involves formation of three separate metastable phases, {l_brace}11{bar 2}0{r_brace}{sub x} platelets of an as yet unidentified phase, and the phases designated {beta}{prime} and {beta}{sub 1}, preceding formation of the equilibrium phase {beta}. All three phases {beta}{prime}, {beta}{sub 1} and {beta} are present in significant fractions in peak-aged samples. The {beta}{prime} phase has a base-centered orthorhombic structure, with a potential point group of mmm. The {beta}{sub 1} phase has a f.c.c. structure (space group Fm{bar 3}m, a = 0.74 {+-} 0.01 nm), which renders it isomorphous with a family of intermetallic compounds of the general form Mg{sub 3}X, where X represents Nd, Ce, La, Pr, Dy and Sm. The equilibrium phase {beta} has an f.c.c. structure (space group, F{bar 4}3m, a = 2.2 {+-} 0.1 nm), which makes it isomorphous with Mg{sub 5}Gd. The formation of B{sub 1} phase is shown to generate significant shear strain energy, and a mechanism of shear strain energy accommodation is proposed, involving nucleation in association with {beta}{prime} phase. With prolonged ageing at 250 C, the {beta}{sub 1} phase transforms in situmore » to the equilibrium {beta} phase.« less

Authors:
;
Publication Date:
Research Org.:
Monash Univ., Clayton, Victoria (AU)
OSTI Identifier:
20075926
Resource Type:
Journal Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 48; Journal Issue: 8; Other Information: PBD: 11 May 2000; Journal ID: ISSN 1359-6454
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; PHASE STUDIES; MAGNESIUM ALLOYS; YTTRIUM ALLOYS; NEODYMIUM ALLOYS; PRECIPITATION; AGING; ELECTRON MICROSCOPY

Citation Formats

Nie, J.F., and Muddle, B.C. Characterization of strengthening precipitate phases in a Mg-Y-Nd alloy. United States: N. p., 2000. Web. doi:10.1016/S1359-6454(00)00013-6.
Nie, J.F., & Muddle, B.C. Characterization of strengthening precipitate phases in a Mg-Y-Nd alloy. United States. doi:10.1016/S1359-6454(00)00013-6.
Nie, J.F., and Muddle, B.C. Thu . "Characterization of strengthening precipitate phases in a Mg-Y-Nd alloy". United States. doi:10.1016/S1359-6454(00)00013-6.
@article{osti_20075926,
title = {Characterization of strengthening precipitate phases in a Mg-Y-Nd alloy},
author = {Nie, J.F. and Muddle, B.C.},
abstractNote = {Strengthening precipitate phases in a Mg-Y-Nd based alloy (WE54), aged at 250 C, have been characterized using transmission electron microscopy. Precipitation at 250 C involves formation of three separate metastable phases, {l_brace}11{bar 2}0{r_brace}{sub x} platelets of an as yet unidentified phase, and the phases designated {beta}{prime} and {beta}{sub 1}, preceding formation of the equilibrium phase {beta}. All three phases {beta}{prime}, {beta}{sub 1} and {beta} are present in significant fractions in peak-aged samples. The {beta}{prime} phase has a base-centered orthorhombic structure, with a potential point group of mmm. The {beta}{sub 1} phase has a f.c.c. structure (space group Fm{bar 3}m, a = 0.74 {+-} 0.01 nm), which renders it isomorphous with a family of intermetallic compounds of the general form Mg{sub 3}X, where X represents Nd, Ce, La, Pr, Dy and Sm. The equilibrium phase {beta} has an f.c.c. structure (space group, F{bar 4}3m, a = 2.2 {+-} 0.1 nm), which makes it isomorphous with Mg{sub 5}Gd. The formation of B{sub 1} phase is shown to generate significant shear strain energy, and a mechanism of shear strain energy accommodation is proposed, involving nucleation in association with {beta}{prime} phase. With prolonged ageing at 250 C, the {beta}{sub 1} phase transforms in situ to the equilibrium {beta} phase.},
doi = {10.1016/S1359-6454(00)00013-6},
journal = {Acta Materialia},
issn = {1359-6454},
number = 8,
volume = 48,
place = {United States},
year = {2000},
month = {5}
}