Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder ...Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder prepared by MA was sintered into a bulk HEA specimen containing FCC phase matrix along with precipitated M 23 C 6 phase and nanoscaleσphase particles.When the sintering temper-ature was 1223 K,the ultimate strength reaches 1300±11.6 MPa,and the elongation exceeds 4%±0.6%.Microstructural characterization reveals that the formation of nanoscale particles and deformation twins play critical roles in improving the strain hardening(SH)ability.Prolonging the MA time promoted the formation of the precipitated phase and enhanced the SH ability by increasing the number of precip-itated particles.The SH capacity increases significantly with increasing sintering temperature,which is attributed to a significant enhancement in the twinning capacity due to grain growth and the reduced number ofσphase particles.Through systematic studies,the planar glide of dislocations was found to be the main mode of deformation,while deformation twinning appeared as an auxiliary deformation mode when the twinning stress was reached.Although the formation of precipitates leads to grain bound-ary and precipitation strengthening effects,crack initiation is more prominent owing to increased grain boundary brittleness around the precipitated M 23 C 6 phase.The prominence of crack initiation is a contra-diction that must be reconciled with regard to precipitation strengthening.This work serves as a useful reference for the preparation of high-strength HEA parts by powder metallurgy.展开更多
基金supported by the National Natu-ral Science Foundation of China(Nos.52061021,51861016,and 51871132)the Science and Technology Major Project of Yun-nan Province(Nos.202202AG050004,202002AB080001)+2 种基金the Young and Middle-Aged Academic and Technical Leaders Reserve Talent Project(No.202005AC160039)support by the Ministry of Science and Higher Educa-tion of the Russian Federation in the framework of the Increase Competitiveness Program of NUST«MISiS»(No.K2-2020-046)financial support from the China Scholarship Council(CSC,No.201906220226).
文摘Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder prepared by MA was sintered into a bulk HEA specimen containing FCC phase matrix along with precipitated M 23 C 6 phase and nanoscaleσphase particles.When the sintering temper-ature was 1223 K,the ultimate strength reaches 1300±11.6 MPa,and the elongation exceeds 4%±0.6%.Microstructural characterization reveals that the formation of nanoscale particles and deformation twins play critical roles in improving the strain hardening(SH)ability.Prolonging the MA time promoted the formation of the precipitated phase and enhanced the SH ability by increasing the number of precip-itated particles.The SH capacity increases significantly with increasing sintering temperature,which is attributed to a significant enhancement in the twinning capacity due to grain growth and the reduced number ofσphase particles.Through systematic studies,the planar glide of dislocations was found to be the main mode of deformation,while deformation twinning appeared as an auxiliary deformation mode when the twinning stress was reached.Although the formation of precipitates leads to grain bound-ary and precipitation strengthening effects,crack initiation is more prominent owing to increased grain boundary brittleness around the precipitated M 23 C 6 phase.The prominence of crack initiation is a contra-diction that must be reconciled with regard to precipitation strengthening.This work serves as a useful reference for the preparation of high-strength HEA parts by powder metallurgy.
