Transition metal diborides(TMB2S)are the materials of choice in extreme environments due to their ex-cellent thermal and chemical stabilities.However,the degradation of oxidation resistance of TMB2s at elevated temperature still hinders their applications.To cope with this challenge,it is effective to incor-porate rare earth elements to form high-entropy transition and rare-earth metal diborides(HE TMREB2s).To obtain thermodynamically stable single-phase structures for HE TMREB2s,a"16×16 mixed enthalpy matrix"is constructed using first-principles calculations to predict the single-phase formation ability of 120 two-component diborides(TCBs).Through the use of the"16×16 mixed enthalpy matrix"of TCBs,specific combinations of TMB2s and REB2s that are most likely to form single-phase HE TMREB2s are confirmed.Subsequently,based on the energy distribution of the local mixing enthalpies of all possible configurations,the enthalpy and entropy descriptors of HE TMREB2s(RE=Sc,Lu,Tm,Er,Ho and Dy)are investigated.It is found that the mixing enthalpy plays a critical role in the stability of the single-phase HE TMREB2s,i.e.,HE TMREB2s are enthalpy-stabilized materials.The experimental results further confirm that enthalpy dominates the thermodynamic domain and drives the stability of REB2s in HE TMREB2s.This study validates that enthalpy-stabilized HE TMREB2s can further expand the compositional space of ultrahigh temperature ceramics(UHTCs)and is expected to further improve the oxidation resistance and high temperature properties of UHTCs.

Ze Zhang;Shizhen Zhu;Fu-Zhi Dai;Huimin Xiang;Yanbo Liu;Ling Liu;Zhuang Ma;Shijiang Wu;Fei Liu;Kuang Sun;Yanchun Zhou

School of Materials Science and Engineering,Beijing Institute of Technology,Beijing 100081,China;Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of Materials and Processing Technology,Beijing 100076,China;National Key Laboratory of Science and Technology on Materials Under Shock and Impact,Beijing 100081,China;Yangtze Delta Region Academy of Beijing Institute of Technology,Jiaxing 314019,China;Beijing Institute of Technology Chongqing Innovation Center,Chongqing 401120,China;Zibo Firststar New Material Incorporated Co.,Ltd.,Zibo 255000,China;Shanghai Chenhua Science and Technology Corporation Ltd.,Shanghai 201804,China

材料科学技术（英文版）

[1]Ze Zhang;Shizhen Zhu;Fu-Zhi Dai;Huimin Xiang;Yanbo Liu;Ling Liu;Zhuang Ma;Shijiang Wu;Fei Liu;Kuang Sun;Yanchun Zhou-.Theoretical predictions and experimental verification on the phase stability of enthalpy-stabilized HE TMREB2s)[J].材料科学技术（英文版）,2022(26):154-162

TMREB2s,diborides,TMB2S,TMB2s,TCBs,REB2s,UHTCs

Theoretical,predictions,experimental,verification,phase,stability,enthalpy,stabilized,HE,Transition,metal,materials,choice,extreme,environments,due,their,cellent,thermal,chemical,stabilities,However,degradation,oxidation,resistance,elevated,temperature,still,hinders,applications,To,cope,this,challenge,effective,incor,porate,rare,earth,elements,entropy,transition,obtain,thermodynamically,stable,single,structures,mixed,matrix,constructed,using,first,principles,calculations,formation,two,component,Through,use,specific,combinations,that,most,likely,confirmed,Subsequently,energy,distribution,local,mixing,enthalpies,possible,configurations,descriptors,Sc,Lu,Tm,Er,Dy,investigated,It,found,plays,critical,role,results,further,dominates,domain,drives,This,study,validates,can,expand,compositional,space,ultrahigh,ceramics,expected,improve,properties

0.443608