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金属学报  2020, Vol. 56 Issue (3): 340-350    DOI: 10.11900/0412.1961.2019.00229
  研究论文 本期目录 | 过刊浏览 |
定向凝固Mg-xGd-0.5Y合金的微观组织及拉伸变形行为
孙衡,林小娉(),周兵,赵圣诗,唐琴,董允
东北大学秦皇岛分校资源与材料学院 秦皇岛 066004
Microstructures and Tensile Deformation Behavior of Directionally Solidified Mg-xGd-0.5Y Alloys
SUN Heng,LIN Xiaoping(),ZHOU Bing,ZHAO Shengshi,TANG Qin,DONG Yun
School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China
全文: PDF(33665 KB)   HTML
摘要: 

研究了Gd含量(3.0%、4.5%、6.0%,质量分数)对定向凝固Mg-xGd-0.5Y合金微观组织及室温力学性能的影响,并利用EBSD技术分析其室温拉伸形变行为。结果表明,在抽拉速率为3 mm/min条件下,Mg-xGd-0.5Y合金获得了纵向晶界与热流方向平行、主要沿(112?0)晶面的法线方向择优生长的柱状晶组织,且柱状晶的横截面呈“三角形”或“十”字形花瓣状,二次分枝由3.0%Gd的3个分枝逐渐变为6.0%Gd的4个分枝。室温下,柱状晶晶体生长取向多集中在<224?3>的Mg-6.0Gd-0.5Y合金具有较高的抗拉强度(107 MPa)和断后延伸率(32.56%),其形变机制以基面<a>滑移和{101?2}拉伸孪生为主。晶体生长取向较为分散(集中在<1?21?0>和<224?3> 2个取向)的Mg-3.0Gd-0.5Y合金形变时,因晶粒取向不同导致孪生机制不同,既有以{101?2}拉伸孪生协调应变的晶粒,也有以{101?1}压缩孪生协调应变的晶粒,各柱状晶协同变形能力较差,故其室温塑性较低,断后延伸率仅有14.88%。

关键词 Mg-Gd-Y合金晶体取向孪生机制断后延伸率    
Abstract

The poor plastic deformation ability of magnesium alloy, resulted from its close-packed hexagonal structure and only two independent basal <a> slip systems at room temperature that cannot meet the von Mises criterion, has extremely restricted its application. As the α-Mg dendrites grow along with the heat flow in directional solidification, the uniform columnar crystal structures obtained in Mg can effectively improve its mechanical properties. And the mechanical properties of the anisotropic magnesium alloys were heavily affected by the orientation controlled by the directional solidification parameters. In this work, the effects of Gd content (3.0%, 4.5%, 6.0%, mass fraction) on the microstructure and mechanical properties of directionally solidified Mg-xGd-0.5Y alloy were investigated. The tensile deformation behavior at room temperature was analyzed by EBSD technique. The results showed that the Mg-xGd-0.5Y alloys have a longitudinal grain boundary parallel to the heat flow direction and a preferential growth along the normal direction of the (112?0) plane at a withdrawn rate of 3 mm/min. The cross section of the columnar crystal was triangle or crisscross petal in shape, and the secondary branch gradually changed from three branches of 3.0%Gd to four branches of 6.0%Gd. The Mg-6.0Gd-0.5Y alloy with more columnar crystal growing along with <224?3> direction had higher tensile strength (107 MPa) and post-break elongation (32.56%) at room temperature, and its deformation mechanism was basal <a> slipping and {101?2} extension twinning. When the crystal growth directions dispersed (concentrated on the <1?21?0> and <224?3>) in the Mg-3.0Gd-0.5Y alloy, it had low post-break elongation (14.88%) because of poor synergistic deformation ability, which have {101?2} extension twins and {101?1} contraction twins to accommodate strain.

Key wordsMg-Gd-Y alloy    crystal orientation    twinning mechanism    post-break elongation
收稿日期: 2019-07-12     
ZTFLH:  TG146.22  
基金资助:国家自然科学基金项目(51775099);国家自然科学基金项目(51675092);河北省自然科学基金项目(E2018501033)
通讯作者: 林小娉     E-mail: 1000629@neuq.edu.cn
Corresponding author: Xiaoping LIN     E-mail: 1000629@neuq.edu.cn
作者简介: 孙 衡,男,1992年生,硕士生

引用本文:

孙衡,林小娉,周兵,赵圣诗,唐琴,董允. 定向凝固Mg-xGd-0.5Y合金的微观组织及拉伸变形行为[J]. 金属学报, 2020, 56(3): 340-350.
Heng SUN, Xiaoping LIN, Bing ZHOU, Shengshi ZHAO, Qin TANG, Yun DONG. Microstructures and Tensile Deformation Behavior of Directionally Solidified Mg-xGd-0.5Y Alloys. Acta Metall Sin, 2020, 56(3): 340-350.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2019.00229      或      https://www.ams.org.cn/CN/Y2020/V56/I3/340

图1  拉伸试样尺寸
图2  Mg-xGd-0.5Y合金定向凝固组织的OM像
图3  Mg-xGd-0.5Y伪二元合金平衡相图
图4  Mg-xGd-0.5Y合金与标准Mg粉的XRD衍射谱
图5  Mg-xGd-0.5Y合金的室温拉伸应力-应变曲线及其特征分布图
图6  定向凝固Mg-6.0Gd-0.5Y合金室温拉伸至变形量为25%的显微组织
图7  定向凝固Mg-6.0Gd-0.5Y合金拉伸形变组织的EBSD分析
图8  定向凝固Mg-3.0Gd-0.5Y合金室温拉伸至变形量为10%时的显微组织
图9  定向凝固Mg-3.0Gd-0.5Y合金拉伸形变组织的EBSD分析
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