The effect of oxygen on the microstructure,mechanical properties and deformation behaviours of as-cast biocompatible Ti40Zr25Nb25Ta10Ox(x=0.5,1.0 and 2.0 at.%)high entropy alloys(HEAs)was investi-gated.All three oxyge...The effect of oxygen on the microstructure,mechanical properties and deformation behaviours of as-cast biocompatible Ti40Zr25Nb25Ta10Ox(x=0.5,1.0 and 2.0 at.%)high entropy alloys(HEAs)was investi-gated.All three oxygen-doped HEAs solidified as a single body-centred cubic(BCC)phase grain structure with predominantly high-angle grain boundaries following the Mackenzie prediction.Increasing oxygen content significantly increased tensile strength at a rate of about 180 MPa/1.0 at.%,but decreased ten-sile ductility.However,at the addition level of 0.5 at.%O,the as-cast Ti40Zr25Nb25Ta10O0.5 HEA can achieve a yield strength(σ_(0.2))of 947±44 MPa and an elongation at break(ε_(f))of 9.5%±1.8%.These properties make this HEA comparable to medical grade Ti-6Al-4V(wt.%)alloy(ASTM Grade 23 titanium)(σ_(0.2)≥759 MPa;ε_(f)≥10%)in itsability to absorbenergy in plasticdeformation,whileoffering greater resistance to permanent shape changes.Due to the possible strong interaction between oxygen atoms and dislocations through pinning and de-pinning,all oxygen-doped HEAs exhibited discontinuous yield-ing,whereas the low oxygen base HEA underwent normal yielding.No oxygen clusters were detected through atom probe tomography(APT)analysis.The deformation mechanism depends on oxygen con-tent.The plastic deformation of the Ti40Zr25Nb25Ta10O0.5 HEA occurred through the formation of pri-mary and secondary shear bands.In contrast,planar slip bands and a limited number of primary shear bands(without secondary shear bands)were observed in the Ti40Zr25Nb25Ta10O2.0 HEA.To ensure suf-ficient ductility,the oxygen content should be limited to 0.5 at.%.Furthermore,at this oxygen content,the corrosion resistance of the Ti40Zr25Nb25Ta10O0.5 HEA in Hank’s solution is comparable to that of Ti-6Al-4V.展开更多
文摘The effect of oxygen on the microstructure,mechanical properties and deformation behaviours of as-cast biocompatible Ti40Zr25Nb25Ta10Ox(x=0.5,1.0 and 2.0 at.%)high entropy alloys(HEAs)was investi-gated.All three oxygen-doped HEAs solidified as a single body-centred cubic(BCC)phase grain structure with predominantly high-angle grain boundaries following the Mackenzie prediction.Increasing oxygen content significantly increased tensile strength at a rate of about 180 MPa/1.0 at.%,but decreased ten-sile ductility.However,at the addition level of 0.5 at.%O,the as-cast Ti40Zr25Nb25Ta10O0.5 HEA can achieve a yield strength(σ_(0.2))of 947±44 MPa and an elongation at break(ε_(f))of 9.5%±1.8%.These properties make this HEA comparable to medical grade Ti-6Al-4V(wt.%)alloy(ASTM Grade 23 titanium)(σ_(0.2)≥759 MPa;ε_(f)≥10%)in itsability to absorbenergy in plasticdeformation,whileoffering greater resistance to permanent shape changes.Due to the possible strong interaction between oxygen atoms and dislocations through pinning and de-pinning,all oxygen-doped HEAs exhibited discontinuous yield-ing,whereas the low oxygen base HEA underwent normal yielding.No oxygen clusters were detected through atom probe tomography(APT)analysis.The deformation mechanism depends on oxygen con-tent.The plastic deformation of the Ti40Zr25Nb25Ta10O0.5 HEA occurred through the formation of pri-mary and secondary shear bands.In contrast,planar slip bands and a limited number of primary shear bands(without secondary shear bands)were observed in the Ti40Zr25Nb25Ta10O2.0 HEA.To ensure suf-ficient ductility,the oxygen content should be limited to 0.5 at.%.Furthermore,at this oxygen content,the corrosion resistance of the Ti40Zr25Nb25Ta10O0.5 HEA in Hank’s solution is comparable to that of Ti-6Al-4V.
