In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstruc...In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.展开更多
The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cub...The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.展开更多
基金Project(2016YFB0700300)supported by the National Key Research and Development Program of China。
文摘In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.
基金the foundation of Westlake University for financial supportThe work at Zhejiang University was supported by the National Key Research and Development Program of China(2017YFA0303002)。
文摘The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.
