Characterisation of strengthening precipitate phases in a Mg-Y-Nd alloy
Characterisation of strengthening precipitate phases in a Mg-Y-Nd alloy
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DOI：
10.1016/s1359-6454(00)00013-6
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发表时间：
2000-05-11
期刊：
影响因子：
9.4
通讯作者：
Muddle, BC
中科院分区：
文献类型：
--
作者：
Nie, JF;Muddle, BC
用透射电镜对250℃时效的Mg-Y-Nd基合金（WE54）中的强化析出相进行了表征。在250℃的沉淀过程中，形成了三个独立的亚稳相，{11 (2)/ bar 0}（α）个尚未确定相的血小板，以及指定为β′和pl的相，在形成平衡相β之前。三相β′、β(1)和β在峰龄样品中均显著存在。相具有以碱基为中心的正交结构，其电位点群为mmm。β(1)相具有fc.c结构（空间群Fm (3) / bar m, a = 0.74+/-0.01 nm），这使得它与一般形式为Mg3X的金属间化合物族同构，其中X代表Nd， Ce, La, Pr， Dy和Sm。平衡相β具有fcc结构（空间群，F(4)大于bar 3m， a = 2.2+/-0.1 nm），使其与Mg5Gd同构。β(1)相的形成可以产生显著的剪切应变能，并提出了一种剪切应变能调节机制，包括与β′相相关的成核。在250℃下延长时效，β(1)相原位转变为平衡β相。(C) 2000金属学报Elsevier Science Ltd.出版。版权所有。
Strengthening precipitate phases in a Mg-Y-Nd based alloy (WE54), aged at 250 degrees C, have been characterised using transmission electron microscopy. Precipitation at 250 degrees C involves formation of three separate metastable phases, {11 (2) over bar 0}(alpha) platelets of an as yet unidentified phase, and the phases designated beta' and pl, preceding formation of the equilibrium phase beta. All three phases beta', beta(1) and beta are present in significant fractions in peak-aged samples. The beta' phase has a base-centred orthorhombic structure, with a potential point group of mmm. The beta(1) phase has an f.c.c. structure (space group Fm (3) over bar m, a = 0.74+/-0.01 nm), which renders it isomorphous with a family of intermetallic compounds of the general form Mg3X, where X represents Nd, Ce, La, Pr, Dy and Sm. The equilibrium phase beta has an f.c.c. structure (space group, F (4) over bar 3m, a = 2.2+/-0.1 nm), which makes it isomorphous with Mg5Gd. The formation of beta(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' phase. With prolonged ageing at 250 degrees C, the beta(1) phase transforms in situ to the equilibrium beta phase. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. AN rights reserved.