摘要
利用DTA、OM、SEM、TEM、EPMA以及拉伸实验等方法研究了在添加α-Al晶粒细化剂Al-Ti-B中间合金和共晶Si变质剂Sr条件下,微合金化元素La对亚共晶Al-Si合金凝固组织与力学性能的影响。结果表明:添加微量稀土La能进一步细化α-Al,变质共晶Si,显著提高合金的塑性。分析表明:微量La能降低α-Al晶核与TiB2的润湿角,减小α-Al的形核过冷度,促进α-Al的进一步细化;La能诱发交错孪晶的形成,增大共晶Si的孪晶密度,改变Si相的长大行为,进一步改变共晶Si的形貌。当La的添加量达到0.10%时,LaAlSi金属间化合物在凝固过程的共晶反应阶段形成,该化合物的形成将降低合金的塑性。
Hypoeutectic Al-Si alloys are extensively used in the welding industry owing to their excellent cast-ability,low coefficient of thermal expansion,and good weldability.Unfortunately,Al-Si alloys solidify under conventional cooling conditions,forming coarse dendriticα-Al grains with an eutectic structure and a flake-like morphology that has poor mechanical properties.Chemical inoculations are often used to control the size ofα-Al grains and the morphology of the eutectic Si particles.The grain refiner Al-Ti-B master alloy and eutectic Si modifier Sr are commonly used in industry.In recent years,great attention has been paid to controlling the microstructure and mechanical properties of hypoeutectic Al-Si alloys through the use of the cost-effective rare earth element La.Previous studies have mainly focused on the effects of La addition on the microstructural evolution and improvements of the mechanical properties.However,to date there have been no studies on the effects of combined addition of La,Al-Ti-B master alloy and Sr on the microstructure and mechanical properties of Al-Si alloys.In this work,solidification experiments were performed to investigate the effects of the micro-alloying element La,Al-Ti-B master alloy,and Sr on the solidification microstructure and mechanical properties of hypoeutectic Al-Si alloys.These results show that synergistic effects are achieved by combinations of La,Al-Ti-B master alloy,and Sr.An addition of 0.06%La was sufficient for effectiveα-Al grain refinement,eutectic Si particle modification,and improved the ductility of the alloys.Excess La addition formed a coarse LaAlSi intermetallic compound,which deteriorated the ductility of the alloy.The micro-alloying element La refined theα-Al grains by acting as a surfactant that decreased the wetting angle between the TiB2 nucleation substrate and theα-Al nucleus.It modified the eutectic Si particles by promoting the formation of the multiple Si twins and changing the growth behaviors of the Si particles.
作者
郑秋菊
叶中飞
江鸿翔
卢明
张丽丽
赵九洲
ZHENG Qiuju;YE Zhongfei;JIANG Hongxiang;LU Ming;ZHANG Lili;ZHAO Jiuzhou(Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China;Electric Power Research Institute of State Grid Henan Electric Power Company,Zhengzhou 450052,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第1期103-110,共8页
Acta Metallurgica Sinica
基金
国家自然科学基金项目Nos.51771210和51971227
国家电网有限公司总部科技项目No.5500-201924129A-0-0-00
关键词
AL-SI合金
微合金化元素La
凝固组织
力学性能
Al-Si alloy
micro-alloying element La
solidification microstructure
mechanical property
