摘要
采用冷金属过渡模式(Cold Metal Transfer,CMT)的同轴送丝电弧熔丝增材制造技术制备了TC4-DT钛合金直壁墙试块,对其高低倍组织及其形成机理进行了研究,使用3D-Rosenthal模型对其凝固过程进行了模拟计算。低倍组织表明,弧形热影响区为细等轴晶,堆积区底层为细柱状晶区,中层和顶层为等轴晶与短柱状晶的混合。这种组织,与电子束熔丝和旁轴送丝电弧熔丝的粗大柱状晶组织有明显的不同;堆积区的高倍组织以编织状的α相板条为主,在部分原始β晶界可见连续的晶界α相和集束状α相板条,且有热影响层界线,与电子束熔丝和旁轴送丝电弧熔丝的高倍组织接近。模拟计算的结果表明,熔池边界的最大温度梯度约为12652.6 K/cm,最大凝固速度约为1.5 cm/s,该凝固条件处于柱状晶-等轴晶转变(Columnar-Equiaxed Transformation,CET)模型中的混合组织区;根据计算结果,提高输入功率(P)和焊枪移动速度(V)可促进等轴晶的生成,当P>153 W、V>3.2 mm/s时可得到柱状晶与等轴晶混合的低倍组织,且晶粒尺寸随着V的增大呈减小的趋势。
A TC4-DT Ti-alloy of two tracks and three layers was manufactured via arc additive manufacturing(CMT WAAM)coupled with cold metal transfer mode coaxial wire feeding,while the TC4-DT Tialloy wire of 1.2 mm in diameter was adoped as feeding wire.The microstructure of the acquired alloy was then characterized.Results show that fine equiaxed priorβ-grains were found in the cambered heat affected zone;The bottom layer of the deposition zone consisted of thin columnar grains;The middle and top layers were composed of equiaxed grains and short columnar grains.Which was quite different from the coarse columnar grains produced by processes of EBRM and TIG WAAM.The microstructure of deposition zone presents basket weaveα-phase laths,similar with that of EBRM and TIG WAAM.The3 D-Rosenthal solution was used to investigate the formation of the microstructure of the deposition zone.The maximum temperature gradient of the molten pool boundary calculated is about 12652.6 K/cm,and the maximum solidification speed is about 1.5 cm/s.The calculated solidification conditions just located in the mixed zone in the columnar-equiaxed-transformation(CET)model,consistent with the experiment results.The calculation results demonstrated that with the increasing input power P and the welding gun traveling speed V,the formation of equiaxed grains was promoted,while the grain size would gradually decrease with the increase of V.The mixed macrostructure would form when P>153 W and V>3.2 mm/s.
作者
杜子杰
李文渊
刘建荣
锁红波
王清江
DU Zijie;LI Wenyuan;LIU Jianrong;SUO Hongbo;WANG Qingjiang(University of Science and Technology of China,Hefei 230026,China;Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;Qingdao Joint X Intelligent Manufacturing Limited,Qingdao 266109,China)
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2020年第7期518-526,共9页
Chinese Journal of Materials Research
