A revisit to the role of Mo in an MP35N superalloy:An experimental and theoretical study  

作　　者：Qing Cheng Jinyong Mo Xiaoqing Li Xiandong Xu 

机构地区：[1]Center for High Resolution Electron Microscopy,College of Materials Science and Engineering,Hunan University,Changsha 410082,China [2]Institute of Massive Amorphous Metal Science School of Materials Science and Physics,China University of Mining and Technology,Xuzhou 221116,China [3]Department of Materials Science and Engineering,Applied Materials Physics KTH-Royal Institute of Technology,Stockholm SE-10044,Sweden

出　　处：《Journal of Materials Science & Technology》2023年第26期60-70,共11页材料科学技术（英文版）

基　　金：financially supported by the Young Scientists Fund of the National Natural Science Foundation of China(No.52001120);the Hunan Provincial National Science Fund for Distin-guished Young Scholars(No.2022JJ10015);the State Key Labora-tory of Advanced Metals and Materials(No.2021-Z09);the Univer-sity of Science&Technology Beijing,China.X.Q.Li was supported by the Swedish Research Council(No.2020-03736);funded by the Swedish Research Council through grant agreement(No.2018-05973)。

摘　　要：Molybdenum(Mo)has been recognized as an essential alloying element of the MP35N(Co_(35.4)Cr_(22.9)Ni_(35.5)Mo_(6.2),at.%)superalloy for enhancing strength and corrosion resistance.However,a full understanding of the addition of Mo on microstructure and mechanical properties of the Mo-free parent alloy is lacking.In this work,we consider five(Co_(37.7)Cr_(24.4)Ni_(37.9))_(100-x)Mo_(x)(x=0,0.7,2.0,3.2,and 6.2)alloys,and reveal that yield/tensile strength and ductility are continuously increased for these alloys with increasing Mo content while a single-phase face-centered cubic structure remains unchanged.It is found that strong solid solution strengthening(SSS)is a main domain to the improved yield strength,whereas grain boundaries are found to soften by the Mo addition.The first-principles calculations demonstrate that a severe local lattice distortion contributes to the enhanced SSS,and the grain boundary softening effect is mostly associated with the decreased shear modulus.Both first-principles calculations and scanning transmission electron microscopy observations reveal that the stacking fault energy(SFE)reduces by the Mo addition.The calculated SFE value decreases from 0.4 mJ/m^(2) to-11.8 mJ/m^(2) at 0 K as Mo content increases from 0 at.%to 6.2 at.%,and experimentally measured values of SFE at room temperature for both samples are about 18 mJ/m^(2) and 9 mJ/m^(2),respectively.The reduction of SFE promoted the generation of stacking faults and deformation twins,which sustain a high strain hardening rate,thus postponing necking instability and enhancing tensile strength and elongation.

关 键 词：Mo addition Solid solution strengthening Grain boundary softening Local lattice distortion First-principles simulations Stacking fault energy Deformation twin 

分 类 号：TG174.4[金属学及工艺—金属表面处理]