Effect Of Hf Substitution Cu On Glass-forming Ability And Properties Of Zr-based Bulk Metallic Glasses

Zr-based bulk metallic glasses have promising application owing to their excellent mechanical,physical and chemical properties.However,the scope of applications is limited due to amorphous glass forming ability and poor plastic properties.Studies have shown that amorphous alloys are very sensitive to elemental changes and compositional changes.Minor additions of alloying elements in to BMGs has been an effective method for developing new metallic glasses with superior GFA,mechanical properties and corrosion resistance.In this paper,based on the Zr₅₅Ti₃Cu₃₂Al₁₀ alloy,the newly BMGs ZrTiHfCuAl were prepared by the copper mold casting method,the effect of Hf substitution Cu on the GFA,mechanical properties and corrosion resistance were studied.The amorphous alloy structure was characterized by X-ray diffraction?XRD?and transmission electron microscopy?TEM?.The thermal properties of the amorphous alloy were analyzed by differential scanning calorimetry?DSC?.Mechanical properties and fracture characteristics of the material were analyzed by scanning?SEM?.Electrochemical measurements were conducted in a three electrode cell using a platinum counter electrode and a saturated calomel reference electrode?SCE?with electrochemical workstation.Through XRD,TEM experimental results,we can know that the substitution of Hf element increase the GFA and the critical dimension of amorphous alloy.The critical size of the initial amorphous alloy Zr₅₅Ti₃Cu₃₂Al₁₀ is 4mm.When addition of Hf content is over 3%,Zr₅₅Ti₃Hf₃Cu₂₉Al₁₀0 have the highest GFA and the largest critical dimension.In addition,the critical dimensions of Zr₅₅Ti₃Hf₄Cu₂₈Al₁₀ and Zr₅₅Ti₃Hf₅Cu₂₇Al₁₀ amorphous alloys reached 6mm.The thermal properties of the amorphous alloy system were characterized by DSC experiments.The analysis of the results shows that with the increase Hf content,the supercooled liquid region of Zr₅₅Ti₃Hf_xCu_32-xAl₁₀?x=0,1,2,3,4,5at.%?amorphous alloy first increases to 70K,and then decreased to 59K,indicated that thermal stability first increases and then decreases.The mechanical properties of Zr₅₅Ti₃Hf_xCu_32-xAl₁₀?x=0,1,2,3,4,5 at.%?BMG were analyzed by compression tests at room temperature.The compression plasticity and the fracture strength increase first and then decreases with the increase the Hf content.The compressive fracture strength of the Zr₅₅Ti₃Hf₃Cu₂₉Al₁₀ was over 1824±35MPa with a large plastic strain above 2.60±0.10%.The results of polarization curves with electrochemical workstation show that the addition of Hf element improves the corrosion resistance of BMGs.In 1mol/LHCl,0.6mol/L NaCl solution,Hf addition increases the corrosion potential and reduces the corrosion current density.Electrochemical tests indicated that the lowest corrosion current density was 1.6±0.1×10^-8 A/cm² for the alloy with x=5 in H₂SO₄ solution.All results demonstrate that the substitution of Cu with Hf can effectively enhance the corrosion resistance of the BMGs.