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中南大学学报(自然科学版)

Journal of Central South University

第49卷    第1期    总第281期    2018年1月

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文章编号:1672-7207(2018)01-0055-09
单β相镁锂合金Mg-11Li-3Al-0.4Y中温拉伸行为
丁洪波1, 2,周海涛1, 2,秦径为1, 2,李夏雷1, 2,刘克明3

(1. 中南大学 材料科学与工程学院,湖南 长沙,410083; 2. 中南大学 有色金属材料科学与工程教育部重点实验室,湖南 长沙,410083; 3. 江西省科学院 江西省铜钨新材料重点实验室,江西 南昌,330029)

摘 要: 采用熔铸、大变形轧制及退火等工艺制备厚度为1 mm的Mg-11Li-3Al-0.4Y合金板材,结合扫描电子显微镜、高温拉伸试验机等实验方法,研究合金在温度范围为50~200 ℃和应变速率范围为0.001~0.1 s-1的中温变形行为、再结晶行为和组织性能。在Arrhenius双曲正弦型方程的基础上构建适用于单β相含稀土镁锂合金的塑性变形本构方程。研究结果表明:对于单β相Mg-11Li-3Al-0.4Y合金,流变应力随变形温度的升高和应变速率的降低而降低,且真应力-真应变曲线中的锯齿波符合动态应变时效中的Portevin-Le Chatelier效应,这是首次在单β相Mg-Li-Al合金中观察到Portevin-Le Chatelier效应。结合断口分析,发现热轧合金板材在中温拉伸过程中,随着温度的升高,合金拉伸断裂方式由较低温度时的准解理断裂转变为较高温度下的韧窝断裂。

 

关键字: Mg-11Li-3Al-0.4Y合金;热变形;Portevin-Le Chatelier效应;动态再结晶;本构方程

Tensile behavior of β-phase Mg-11Li-3Al-0.4Y alloy at medium temperature
DING Hongbo1, 2, ZHOU Haitao1, 2, QIN Jingwei1, 2, LI Xialei1, 2, LIU Keming3

1. School of Materials Science and Engineering, Central South University, Changsha 410083, China; 2. Key Laboratory of Nonferrous Metal Materials Science and Engineering of Ministry of Education, Central South University, Changsha 410083, China; 3. Jiangxi Key Laboratory of Advanced Copper and Tungsten Materials, Jiangxi Provincial Academy of Science, Nanchang 330029, China

Abstract:New β-phase Mg-11Li-3Al-0.4Y alloy sheet with thickness of 1 mm was prepared by casting, hot-rolling and annealing processes. The fracture morphology and mechanical properties were investigated with scanning electron microscope and medium-temperature stretch test machine, respectively. Additionally, constitutive equation including flow stress, strain rate and deformation temperature was established by hyperbolic sine model with Zene-Hollomon parameter. The results show that the flow stress decreases with the increase of deformation temperature and reduction of strain rate. A pronounced post-relaxation effect followed by a serrated flow curve is shown in true stress-strain curves with low strain rate, which is also called the Portevin-Le Chatelier effect, and it is the first time that Portevin-Le Chatelier effect appears in β-phase Mg-Li-Al alloy. Cleavage fracture is replaced by dimple fracture with the increase of deformation temperature, according to the observation of electron microscope.

 

Key words: Mg-11Li-3Al-0.4Y alloy; thermal deformation; Portevin-Le Chatelier effect; dynamic recrystallization; constitutive equation

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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