Achieving strength-ductility synergy in novel paramagnetic Fe-based medium-entropy alloys through deep cryogenic deformation  

作　　者：Hu-Wen Ma Yan-Chun Zhao Li Feng Tian-Zeng Liu Zhi-Qi Yu Bo Jin Wang-Chun Duan Peter K.Liaw Dong Ma 

机构地区：[1]State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China [2]Wenzhou Pump and Valve Engineering Research Institute,Lanzhou University of Technology,Wenzhou 325105,China [3]Iron and Steel Research Institute,Jiuquan Iron and Steel Corporation,Jiayuguan 735100,China [4]Lanzhou Resources and Environment Voc-Tech University,Lanzhou 730123,China [5]Department of Materials Science and Engineering,The University of Tennessee,Knoxville,TN 37996-2200,USA [6]Neutron Science Center,Songshan Lake Materials Laboratory,Dongguan 523808,China

出　　处：《Rare Metals》2024年第9期4493-4507,共15页稀有金属（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.52061027 and 52130108);Zhejiang Provincial Natural Science Foundation of China(No.LY23E010002);the Science and Technology Program Project of Gansu Province(Nos.22YF7GA155 and 22ZD6GA008);Lanzhou Youth Science and Technology Talent Innovation Project(No.2023-QN-91)。

摘　　要：Cryogenic pre-deformation treatment has been widely used to effectively improve the comprehensive mechanical properties of steels and novel metals.However,the dislocation evolution and phase transformation induced by different degrees of deep cryogenic deformation are not yet fully elucidated.In this study,the effects of multiple cryogenic pre-treatments on the mechanical properties and deformation mechanisms of a paramagnetic Fe_(63.3)Mn_(14-)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloy(MEA)were investigated,leading to the discovery of a pretreated MEA that exhibits exceptional mechanical properties,including a fracture strength of 3.0 GPa,plastic strain of 26.1%and work-hardening index of 0.57.In addition,X-ray diffraction(XRD)and transmission electron microscopy(TEM)analyses revealed that multiple cryogenic pre-deformation treatments significantly increased the dislocation density of the MEA(from 9×10^(15)to 4×10^(16)m^(-2)after three pretreatments),along with a transition in the dislocation type from predominantly edge dislocations to mixed dislocations(including screw-and edge-type dislocations).Notably,this pretreated MEA retained its paramagnetic properties(μ_(r)<1.0200)even after fracture.Thermodynamic calculations showed that cryogenic pretreatment can significantly reduce the stacking fault energy of the MEA by a factor of approximately four(i.e.,from 9.7 to2.6 m J·m^(-2)),thereby activating the synergistic effects of transformation-induced plasticity,twinning-induced plasticity and dislocation strengthening mechanisms.These synergistic effects lead to simultaneous strength and ductility enhancement of the MEA.

关 键 词：Deep cryogenic transformation Iron-based medium-entropy alloys Dislocation evolution Phase transformation Stacking fault energy 

分 类 号：TG139[一般工业技术—材料科学与工程]