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.
