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金属学报  2020, Vol. 56 Issue (5): 723-735    DOI: 10.11900/0412.1961.2019.00292
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张阳, 邵建波, 陈韬, 刘楚明, 陈志永()
中南大学材料科学与工程学院 长沙 410083
Deformation Mechanism and Dynamic Recrystallization of Mg-5.6Gd-0.8Zn Alloy During Multi-Directional Forging
ZHANG Yang, SHAO Jianbo, CHEN Tao, LIU Chuming, CHEN Zhiyong()
School of Materials Science and Engineering, Central South University, Changsha 410083, China
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以含长周期堆垛有序(LPSO)相的Mg-5.6Gd-0.8Zn (质量分数,%)合金为研究对象,分析了合金多向锻造过程中的变形机制、动态再结晶及显微组织演变。结果表明:变形初期,{101ˉ2}拉伸孪生仅在部分晶粒中激发;随锻造方向的改变,不同晶体取向的晶粒能够激发孪生变形,孪生体积分数增加,孪生变体选择符合Schmid定律。孪生受阻碍的晶粒通过滑移及扭折协调变形,扭折带类型主要为转轴分布在<101ˉ0>晶向的基面扭折。多向锻造过程中,晶界处优先发生动态再结晶;随着变形量的增加,晶界处再结晶体积分数增大,晶内孪晶与扭折界面诱发再结晶,孪晶逐渐演变为条带状细晶组织。在孪晶、扭折带切割晶粒,晶界再结晶,孪晶、扭折带诱发再结晶多重机制的共同作用下,原始粗晶组织得到了显著细化。

关键词 镁合金LPSO相多向锻造变形机制动态再结晶    

Multi-directional forging (MDF) is an effective way to fabricate wrought magnesium alloy with ultrafine grains and random texture. Therefore, microstructure evolution and dynamic recrystallization (DRX) of magnesium alloys during MDF process have been widely investigated. Mg-Zn-RE alloys containing long-period stacking ordered (LPSO) phase have received considerable attention owing to their excellent mechanical properties. In addition, LPSO phase has great effects on the deformation mechanism and DRX behavior. Still, limited comprehensive studies can be found in the literature dealing with the microstructure evolution, deformation mechanism and DRX of magnesium alloys containing LPSO phase in MDF deformation. In this work, MDF was applied to a Mg-5.6Gd-0.8Zn (mass fraction, %) alloy containing LPSO phase. Microstructure characteristics, deformation mechanism and DRX behavior of the material in different passes were examined. Results show that there are several stages of the microstructure evolution. Twinning was activated only in a small part of grains in the early stage of deformation. As the forging direction changes, the number of twinned grains and the volume fraction of DRX grains increased. A mixed structure with coarse deformed grain and DRX grains was sustained till last forging pass, and the average size of DRX grains is about 4 μm with a random orientation. {101ˉ2} tensile twinning is the main deformation mechanism and the selection of twin variants was dominated by the Schmid law. Change in forging direction is beneficial to twinning stimulation in grains of different orientations. Kink and slipping deformation could effectively accommodate the plastic strain where the operation of twinning was hindered. Kink deformation resulted in lattice rotation predominately about the <101ˉ0> axis. DRX grains nucleated at different places during the forging process. Not only the grain boundaries and the twinned region, but also kink boundaries can induce the nucleation of DRX grains. Eventually, the twinned regions were transformed to a strip-like recrystallization structure. Under the combined influence of twinning and kinking, as well as DRX induced by twins, kink bands and grain boundaries, the initial coarse grains were significantly refined.

Key wordsmagnesium alloy    LPSO phase    multi-directional forging    deformation mechanism    dynamic recrystallization
收稿日期: 2019-09-05     
ZTFLH:  TG146.2  
通讯作者: 陈志永     E-mail:
Corresponding author: CHEN Zhiyong     E-mail:
作者简介: 张 阳,女,1995年生,硕士


张阳, 邵建波, 陈韬, 刘楚明, 陈志永. Mg-5.6Gd-0.8Zn合金多向锻造过程中的变形机制及动态再结晶[J]. 金属学报, 2020, 56(5): 723-735.
Yang ZHANG, Jianbo SHAO, Tao CHEN, Chuming LIU, Zhiyong CHEN. Deformation Mechanism and Dynamic Recrystallization of Mg-5.6Gd-0.8Zn Alloy During Multi-Directional Forging. Acta Metall Sin, 2020, 56(5): 723-735.

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图1  多向锻造流程及微观组织观测取样位置示意图
图2  铸态、均匀化态及退火态Mg-5.6Gd-0.8Zn合金的SEM像
图3  退火态合金长周期堆垛结构(LPSO)相的STEM像
图4  退火态合金锻后各道次显微组织的OM像
图5  多向锻造过程中孪生及扭折诱发再结晶
图6  合金锻后各道次样品SEM像
图7  多向锻造过程中的动态再结晶行为示意图
图8  合金锻后各道次取向成像图
图9  合金1道次锻造后孪生及未孪生晶粒取向成像图、{0001}极图及孪生与基面滑移Schmid因子分析
图10  合金2道次锻造后同一晶粒内的孪生及扭折现象分析
图11  合金3道次锻造后孪生晶粒取向成像图、极图及孪生变体Schmid因子分析
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