摘要
采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)、拉伸力学试验机、显微硬度计和透射电镜(TEM)等分析手段,研究了稀土Er含量和时效工艺对A356合金显微组织和力学性能的影响。结果表明,不同Er含量A356合金的组织都由浅色初生α-Al相和深色共晶硅相组成,随着Er含量(质量分数)从0%增加至0.7%,二次枝晶臂间距逐渐减小,粗大针状共晶硅相逐渐转变为短棒状或者颗粒状,当Er含量为0.7%时合金基体中还发现了针状富Er相;随着时效温度的升高和时效时间的延长,不同Er含量的A356-Er合金的硬度都呈现先增加而后减小的特征,在时效温度175℃、时效时间6 h时,A356-0.3Er合金具有最高的硬度;随着Er含量增加,铸态和热处理态A356-Er合金的抗拉强度、屈服强度和断后伸长率都呈现先增加而后减小的特征,在Er含量为0.3%时取得最大值,这主要与Er元素的添加可以改善共晶硅相形态,以及起到固溶强化和弥散强化的作用有关。
Effects of Er content and aging process on microstructure and mechanical properties of A356 alloy were studied by means of metallographic microscope(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD),tensile mechanical testing machine,microhardness tester and transmission electron microscopy(TEM).The results show that the microstructure of A356 alloy with different Er content is composed of light colour primary alpha-Al phase and dark eutectic silicon phase.With Er content increasing from 0%to 0.7%(mass fraction),the distance between secondary dendrite arms decreases gradually,and the coarse acicular eutectic silicon phase gradually transforms into short rod or granular,and when Er content is 0.7%,acicular Er-rich phase can be also observed in the alloy matrix.The hardness of A356-Er alloys with different Er content increases first and then decreases with the increase of aging time,the hardness of A356-0.3Er alloys reaches the highest at 175℃with aging time for 6 h.With the increase of Er content,the tensile strength,yield strength and elongation at break of as-cast and heat-treated A356-Er alloys increase first and then decrease,and the maximum value is obtained when Er content is 0.3%,which is mainly related to the improvement of eutectic silicon phase morphology by adding Er element,as well as the role of solid solution strengthening and dispersion strengthening.
作者
陈媛媛
王社则
田博彤
Chen Yuanyuan;Wang Sheze;Tian Botong(Shanxi Traffic Vocational and Technical College,Taiyuan Shanxi 030031,China;School of Materials Science and Engineering,Taiyuan University of Technology,Taiyuan Shanxi 030024,China)
出处
《金属热处理》
CAS
CSCD
北大核心
2019年第11期39-44,共6页
Heat Treatment of Metals
基金
国家重点研发计划(2016YFB0301001)
山西省重点研发计划(2017KKJH)
关键词
稀土Er
A356合金
时效工艺
组织
力学性能
rare earth Er
A356 alloy
aging process
microstructure
mechanical properties
作者简介
陈媛媛(1980—),女,讲师,硕士,主要从事有关汽车制造的教学和工艺研究,联系电话:18935192975,E-mail:cyy-8006@163.com。
