文献类型：期刊文献

英文题名：Optimized bilateral ultrasonic surface rolling process assisting directed energy deposition of thin-walled medium-entropy alloy with high mechanical performance

作者：Chen, Yufei[1];Lu, Tiwen[1];Chen, Xiyu[1];Sun, Binhan[1];Yao, Ning[1];Li, Kaishang[1];Qiu, Jihang[1];Hu, Xiaoqi[2];Zhang, Xian-Cheng[1];Tu, Shan -Tung[1]

机构：[1]East China Univ Sci & Technol, Key Lab Pressure Syst & Safety, Minist Educ, Shanghai 200237, Peoples R China;[2]Inst Adv Addit Mfg, Ji Hua Lab, Foshan 528200, Peoples R China

年份：2023

卷号：78

外文期刊名：ADDITIVE MANUFACTURING

收录：;EI(收录号：20234815131799);WOS:【SCI-EXPANDED(收录号:WOS:001165126800001)】；

基金：This work was financially supported by the National Key Research and Development Project (Grant No. 2022YFB4602100) , National Nat- ural Science Foundation of China (Grant No. 52205152, No. U21B2077, and No. 52275147) . Binhan Sun acknowledges the financial support from the Science Center for Gas Turbine Project from China (Project No. P2022 -C -III -002-001) .

语种：英文

外文关键词：Directed energy deposition; Optimized bilateral USRP; Gradient nanotwinned substructure; Strength-ductility balance; Fatigue behavior

摘要：Laser directed energy deposition (DED) offers significant advantages for the integral manufacturing of large-scaled thin-walled workpieces. Nevertheless, how to improve the yield strength (YS) and fatigue properties of thin-walled parts fabricated by DED is a crucial issue. As an advanced surface strengthening technology, ultrasonic surface rolling process (USRP) is aimed to improve the mechanical performances of additively manufactured workpieces. In this work, an optimized bilateral USRP parameter (including the load, repeated times, scanning speed, etc.) with high manufacturing efficiency and surface integrity was developed to fabricate thin-walled CoCrNi medium-entropy alloy (MEA) parts (similar to 1.5 mm thickness). Compared to the as-deposited sample, the sample treated by USRP shows a good strength-ductility balance (ultra-high YS and ductility with 1026.6 MPa and 21.9%, respectively), as well as an impressive improvement in the high-cycle fatigue limit strength of 76.9%. The reasons for high mechanical performance are revealed through multi-scale characterization and calculation. Ultra-high strength is predominantly attributed to the high-density pre-existing dislocations and deformation twins (DTs); Good ductility is related with high hetero-deformation induced stress and the activation of multiple deformation substructures induced by high flow stress, such as dislocations, DTs and hexagonal close-packed phase. Further, the improvement in fatigue performance is ascribed to the closure of manufacturing defects in the surface or subsurface and inhibited surface roughening behavior from stable gradient nanotwinned layer. Finally, the work reveals the quantitative relationship among processing-properties-promotion mechanism (PPP), which provides a criterion to meet the specific mechanical performance of DEDed thin-walled components by precisely tuning the bilateral USRP parameters.