摘要
随着稀土镁合金商业化应用的增加,利用高丰度稀土元素制备更低成本、更高性能的镁合金具有显著优势,但稀土元素的添加完全改变了基体镁合金的合金化顺序,因此,深入研究Ce元素对镁合金的强化机理很有必要。本工作通过第一性原理计算可能存在的Mg-Ce、Al-Ce、Mg-Al强化相的热力学稳定性,采用SEM、XRD、EDS等实验手段分析所制备镁合金样品的物相组成,进而验证第一性原理计算结果,并推导关键稀土中间相的组成及析出顺序。接着,基于错配度理论探讨优先析出的第二相能否成为初生α-Mg的形核核心,揭示Ce元素对镁合金的变质机理;然后以温度为维度,借助Al-Ce、Mg-Al二元相图和Al-Ce-Mn三元相图将不同温度阶段的合金化反应与电负性理论相关联,从而简化多元合金体系中的复杂合金化问题,最终阐明Ce元素对镁合金强化作用机理。研究结果表明,Ce元素添加后将形成大量沿晶界或贯穿晶粒分布的针状或棒状Al_(11)Ce_(3)和Al_(10)Ce_(2)Mn_(7)相,但优先析出的Al_(11)Ce_(3)、Al_(10)Ce_(2)Mn_(7)相并不能作为初生α-Mg的形核核心,晶粒细化机制为晶界位置的第二相阻碍晶粒长大;拉伸实验结果表明,通过调节Ce元素的添加量形成适量Al-Ce相与Mg-Al相混合的结构有利于提高镁合金室温、高温力学性能。
Since the commercial application of rare earth magnesium alloys is increasing gradually,there are considerable advantages to prepare lower cost and higher performance magnesium alloys with a high abundance rare earth(RE)elements.However,the addition of RE elements completely changes the alloying order of the matrix magnesium alloy.Therefore,further study the strengthening mechanism of Ce element on magnesium alloy is required.In this work,thermodynamic stability of the may existing Mg-Ce,Al-Ce and Mg-Al phases were analyzed based on first-principles calculations,and the results were examined through SEM,XRD,EDS and other experimental methods.Moreover,the compositions and precipitation sequence of the key RE phases were deduced as consequence.Then,whether the preferentially precipitated second phase can be the nucleating core of primaryα-Mg was discussed based on the mismatch theory,and the modification mechanism of Ce on magnesium alloy was revealed as result.On the other hand,the complex alloying problem in multi-component magnesium alloy system was simplified with the aid of electronegativity theory,which was associated with the alloying reactions at different temperature stages based on Al-Ce,Mg-Al binary phase diagrams and Al-Ce-Mn ternary phase diagrams.Accordingly,the strengthening mechanism of the Ce addition on magnesium alloys was clarified with the temperature as a dimension.The results of this work show that large numbers of needle-like Al_(11)Ce_(3) phase or rod-likeAl_(10)Ce_(2)Mn_(7) phases would form preferentially and distribute along the grain boundaries or through grains after the adding of Ce element.However,the preferentially precipitated Al_(11)Ce_(3) and Al_(10)Ce_(2)Mn_(7) phases cannot be the nucleating core of primaryα-Mg,which means the grain refinement mechanism is that the second phase at grain boundary prevents the growth of magnesium grain.Besides,the tensile test results show that the formation of an appropriate amount of Al-Ce phase and Mg-Al phase reinforced hybrid structure is beneficial to improve the ambient temperature and high-temperature mechanical properties of magnesium alloys,which could achieve by adjusting the amount of Ce element added.
作者
陈燕飞
朱政强
汪光鑫
Chen Yanfei;Zhu Zhengqiang;Wang Guangxin(School of Advanced Manufacturing,Nanchang University,Nanchang 330031,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2022年第10期3762-3776,共15页
Rare Metal Materials and Engineering
基金
江西省重点研发计划(20203BBG73070)
江西省自然科学基金-面上项目(20202BABA204009)。
关键词
稀土
镁合金
铈
强化机理
第一性原理
rare earth
magnesium alloy
cerium
strength mechanism
first principles
