Designing And Electrochemical Corrosion Behavious Of Zr-Ti-Ni-Cu-Be High Entropy Bulk Metallic Glasses

Owing to the high entropy effect,the lattice distortion effect,sluggish diffusion and the“cocktail”effect,high-entropy alloys exhibit excellent mechanical properties.Bulk metallic glasses possess excellent mechanical,physical and chemical properties due to short-range order and long-range disordered structural features.High-entropy alloys have high mixing entropy and alloy element content,and tend to form high-entropy disordered phases,such as solid solution or amorphous.High-entropy metallic glasses are combined the characteristics of high-entropy alloys and amorphous alloys,and have broad application prospects.However,the low glass forming ability of high-entropy bulk metallic galsses limit their applications in many fields.Therefore,it is great important to develop high-entropy bulk metallic glasses with large glass forming ability and good performance.Zr-Ti-Ni-Cu-Be is a typical bulk metallic glasses system with large glass forming ability.This subject combines high-entropy alloy and amorphous alloy by adding proper elements in Zr-Ti-Ni-Cu-Be alloy system.By analyzing the effects of atomic size difference(?),mixed enthalpy(?H_mix),mixed entropy(?S_mix),valence electron concentration(VEC)and electronegativity difference(??)on the glass formation ability of alloys,the Zr_xTi Ni Cu Be(x=1.5,2,2.5,3,and 3.5 at.%)and Zr₂Ti Ni Cu Be_1-xCo_x(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7,and 1 at.%)alloy systems were designed.The designing alloys were prepared by suction casting.Zr_xTi Ni Cu Be(x=1.5?2?2.5?3 and 3.5at.%)and Zr₂Ti Ni Cu Be_1-xCo_x(x=0.1?0.2?0.3 and 0.4at.%)are both amorphous strcture.The glass transition temperature(T_g)and undercooled liquid region?T_x(?T_x=T_x-T_g)of these alloys are from620K to 680K and 37K to 54K respectively,which showing higher glass forming ability and thermal stability.The structure of Zr₂Ti Ni Cu Be_1-xCo_x(x=0.5?0.6?0.7 and 1at.%)alloys are simple cubic soliolution structure.High entropy bulk metallic glass possess the excellent corrosion resistance due to uniform microstructure and high mixing element content.the electrochemical corrosion bahavior of designed alloys was investigated.The self-corrosion current density of the Zrx Ti Ni Cu Be(x=1.5?2?2.5?3 and 3.5at.%)and Zr₂Ti Ni Cu Be_1-xCo_x(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7and 1at.%)is on the order of 10^-8(A?cm^-2)in the 1mol/L H₂SO4 solution,which is about 1/1000 of 304L stainless steel.The blunt current density is on the order of 10^-6(A?cm^-2),still lower than 304L stainless steel,passivation interval is1.4V.In 1mol/L Zr_xTi Ni Cu Be(x=1.5?2?2.5?3 and 3.5at.%)is similar with Ti-alloys,and Zr₂Ti Ni Cu Be_1-xCo_x(x=0.1?0.2?0.3?0.4?0.5?0.6?0.7 and 1at.%)is similar with Cu-alloys.In 1mol/L Na OH solution,the self-corrosion current density of the designed alloy is1.6246×10-7 A?cm^-2,which is about one quarter of 304L stainless steel,the blunt current density is on the order of 10^-6(A?cm^-2)(except Zr2Ti Ni Cu Co)lower than 304L stainless steel.In 3.5%Na Cl solution,the self-corrosion current density of most component alloys is on the order of 10^-8(A?cm^-2),which is about one tenth of 304L stainless steel.Zr₂Ti Ni Cu Be_1-xCo_x(x=0.3,0.7 and 1 at.%)is on the order of 10^-7(A?cm^-2).The pitting potential is-0.1 V on average which is lower than 304L stainless steel(-0.0574 V).The cyclic polarization curve exists pitting potential and pitting transformation potential,which certifies above alloys all possess pitting repair ability.Zr_xTi Ni Cu Be(x=1.5?2?2.5?3 and3.5at.%)is similar with Ti-alloys,Zr₂Ti Ni Cu Be_1-xCo_x(x=0.1?0.2?0.3?0.4?0.5?0.6?0.7 and 1at.%)is between Ti-alloys and Al-alloys.