Tremendous efforts have been dedicated to promote the formation ability of high-entropy transition metal carbides.However,the majority of methods for the synthesis of high-entropy transition metal car-bides still face the challenges of high temperature,low efficiency,additional longtime post-treatment and uncontrollable properties.To cope with these challenges,high-entropy transition metal carbides with regulatable carbon stoichiometry(HE TMCx)were designed and synthesized,achieving improved ability for single phase solid solutions formation,promoting of sintering and controllable mechanical proper-ties.Two typical composition series,i.e.,easily synthesized(Zr0.25Hf0.25Ta0.25Nb0.25)C(ZHTNC)and diffi-cultly synthesized(Zr0.25Hf0.25Ta0.25Ti0.25)C(ZHTTC)are selected to demonstrate the promoting formation ability of single phase solid solutions from carbon stoichiometry deviations.Single phase high-entropy ZHTTC,which has been proven difficult in forming a single phase solid solution,can be prepared with the decrease of C/TM ratio under 2000℃;while the high-entropy ZHTNC,which has been proven easy in forming a single phase solid solution,can be synthesized at lower temperatures with the decrease of C/TM ratio.The synergistic effect of entropy stabilization and reduced chemical bond strength gaining from carbon stoichiometry deviations is responsible for the formation of single phase solid solutions and the promoted sintering of HE TMCx.For example,the relative density of bulk(Zr0.25Hf0.25Ta0.25Nb0.25)Cx(SPS-ZHTNCx)increases from 90.98％to 94.25％with decreasing the C/TM atomic ratio from 0.9 to 0.74.More importantly,the room temperature flexural strength,fracture toughness and brittleness index of SPS-ZHTNCx can be tuned in the range of 384 MPa-419 MPa,4.41 MPa·m1/2-4.73 MPa·m1/2 and 3.679 um-1/2-4.083 um-1/2,respectively.Thus,the HE TMCx prepared by adjusting the ratio of carbon to re-fractory transition metal oxides have great potential for achieving low temperature synthesis,promoted sintering and tunable properties.

Juntao Song;Guiqing Chen;Huimin Xiang;Fuzhi Dai;Shun Dong;Wenbo Han;Xinghong Zhang;Yanchun Zhou

Science and Technology on Advanced Composite in Special Environments Laboratory,Harbin Institute of Technology,Harbin,150080,China;Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of Materials&Processing Technology,Beijing,100076,China

材料科学技术（英文版）

[1]Juntao Song;Guiqing Chen;Huimin Xiang;Fuzhi Dai;Shun Dong;Wenbo Han;Xinghong Zhang;Yanchun Zhou-.Regulating the formation ability and mechanical properties of high-entropy transition metal carbides by carbon stoichiometry)[J].材料科学技术（英文版）,2022(26):181-189

bides,longtime,TMCx,25Hf0,25Ta0,ZHTNC,cultly,ZHTTC,ZHTNCx,fractory

Regulating,formation,ability,mechanical,properties,high,entropy,transition,metal,carbides,by,carbon,stoichiometry,Tremendous,efforts,have,been,dedicated,However,majority,methods,synthesis,still,face,challenges,efficiency,additional,post,treatment,uncontrollable,To,cope,these,regulatable,HE,were,designed,synthesized,achieving,improved,single,phase,solid,solutions,promoting,sintering,Two,typical,composition,series,easily,Zr0,25Nb0,25Ti0,selected,demonstrate,from,deviations,Single,which,proven,difficult,forming,can,prepared,decrease,ratio,under,while,easy,lower,temperatures,synergistic,effect,stabilization,reduced,chemical,bond,strength,gaining,responsible,promoted,For,example,relative,density,bulk,SPS,increases,decreasing,atomic,More,importantly,room,flexural,fracture,toughness,brittleness,tuned,range,m1,um,respectively,Thus,adjusting,oxides,great,potential,tunable

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