【作者】 郭莹；

【导师】 崔建忠；

【作者基本信息】 东北大学 ， 材料工程（专业学位）， 2020， 硕士

【摘要】 本课题是国家自然基金重点项目《洁净、均质、细晶铝锂合金锭坯制备基础研究》的一部分,旨在为铝锂合金废料回收提供基础数据。本实验以2A97和1420两种典型的铝锂合金废料为研究对象,采用熔盐覆盖法进行重新熔炼,探究了的覆盖剂厚度和成分、加热方式、废料形态(块状和屑状)、纯铝中废料添加量和除气剂添加量对二种铝锂合金重熔时锂及主合元素烧损的影响,借助原子吸收光谱分析法(AAS)、感耦等离子体原子发射光谱法(ICP)、金相组织观察、铸锭缺陷超声波无损检测、X射线衍射(XRD)和电子探针能谱分析等手段,研究重熔后铸锭的缺陷的特征、夹杂物种类和元素分布等。主要结论如下:(1)2A97和1420合金块状废料重熔时,最优覆盖剂厚度均为10mm,随着覆盖剂厚度的增加,夹杂物增多。2A97合金废料重熔时,最优覆盖剂的成分为70%KCl与30%LiCl的混合物添加3%的CaF2,此时锂烧损率为10%;1420合金废料重熔时,最优覆盖剂成分为60%LiCl与40%LiF的混合物添加3%的CaF2,此时锂烧损率为10%。添加冰晶石后,锂烧损率增加,夹杂物显著增加。(2)在纯铝中添加2A97合金废料和1420合金废料合金重熔,当废料质量占比达到50%时,锂元素烧损率达到最低,而后趋于稳定。随着废料加入量增多,缺陷和夹杂增多。同一铸锭中底部夹杂物较多,中上部较少。杂质多为氧化物和非金属夹渣,一般存在于晶界处。(3)铝锂合金重熔时,加热时间越长,锂烧损率越高,中频炉加热优于电阻炉加热,中频炉加热锂烧损率为10%;废料尺寸对锂烧损影响和大,屑状废料锂烧损率远大于块状废料。(4)2A97合金废料重熔,随除气剂加入量增加,锂的烧损增加,加入除气剂后杂质减少,但随着除气剂加入量增多,缺陷和夹杂物增多。更多还原

【Abstract】 This work is a part of project of the preparation of clean,homogeneous,fine-grained aluminum-lithium alloy ingots,a key project of the National Natural Science Foundation of China,and aims to provide basic data for aluminum-lithium alloy waste recycling.In this study,two typical aluminum-lithium alloy waste materials,2A97 and 1420,are used as research objects.Al-Li alloy wastes were remelted with molten salt coating.Effects of the covering agent thickness and composition,heating methods,waste sizee(scrap and bulk),the addition amount of the wastes into pure Al and degassing agent amount on Li loss were worked out.The characteristics of defects,types of inclusions and element distribution in ingots remelted by the atomic absorption spectrum(AAS),bulk atomic emission spectrometry(ICP),metallographic observation(OM),ultrasonic non-destructive testing,X-ray diffraction(XRD),and electronic probe energy spectrum.The main results are as follows:(1)When the bulk 2A97 and 1420 alloy wastes are remelted,the optimal thickness of the covering agent is 10 mm.As the thickness of the covering agent increased,the inclusions increased.When the 2A97 alloy waste is remelted,the optimal covering agent composition is 70%KCl and 30%LiCl,the lithium loss rate is 10%.When the 1420 alloy waste is remelted,the optimal covering agent composition is 60%LiCl and 40%LiF,the lithium loss rate is 10%.In addition,after adding cryolite,the lithium loss rate increased and the inclusions increased significantly.(2)Adding 2A97 and 1420 alloy waste to liquid pure aluminum.When the weight of waste reaches 50%,the loss rate of lithium element reaches the lowest,and then it kept constant.As the adding amount of waste increases,defects and inclusions increase.In the an ingot,there are more inclusions in the bottom and less in the upper and middle parts.Impurities are mostly oxides and non-metallic slags,which generally exist at the grain boundaries.(3)Comparing different heating methods,the longer the heating time,the higher the lithium loss rate.Heating by the intermediate frequency induction furnace is better than the resistance furnace heating,10%lithium burn-off rate at medium frequency heating.Comparing the different waste size,the lithium loss rate of the scrap waste is much larger than that of bluk waste.(4)The larger the degassing agent amount,the higher the lithium loss rate.After degassing the impurities are reduced.However,the defects and inclusions increased as the amount of degassing agent amount increased.更多还原