Development Of A New Biomedical Zr-based Bulk Amorphous Alloy

Currently,amorphous alloy materials are highly valued as structural or functional materials in many fields due to their excellent mechanical and corrosion resistance properties.Among these,Zr-based amorphous alloys have the unique advantage of low modulus of elasticity and good biocompatibility,making them promising candidates for biomedical materials.However,most of the Zr-based bulk amorphous alloy systems developed so far contain elements that are harmful to humans,such as Ni and Be,or precious metals such as Pd and Ag.Therefore,it is imperative to develop a low-cost and biocompatible amorphous alloy system.In this paper,a new composition Zr58TixAl15-x/2Co15-x/2Cu8Fe4 has been developed based on the Zr-based amorphous alloy system ZrCoAl.The resulting amorphous alloy exhibits strong glass formation(up to 5 mm)and excellent mechanical properties.In this paper,Zr-based bulk amorphous alloys of different compositions were prepared by arc melting and suction casting methods.Subsequently,the microstructure,thermal stability,mechanical properties(compressive properties,elastic modulus and hardness)and corrosion resistance of Zr58TixAl15-x/2Co15-x/2Cu8Fe4(x=0～5)bulk amorphous alloy materials were systematically investigated using various experimental methods.This included X-ray diffraction(XRD),differential scanning calorimetry(DSC),a universal mechanical testing machine,an electrochemical workstation,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and a nanoindentation tester and the effect of Ti addition on the properties of amorphous alloy systems.Firstly,amorphous alloy rods with diameters ranging from 2mm to 7mm were prepared and structurally analyzed using X-ray diffraction(XRD).The results showed that the Ti2 composition exhibited the best glass forming ability in this system,being able to form cast alloy rods of at least 5 mm.Subsequently,the material was analysed by DSC and it was found that the Tg glass transition temperature of the system gradually decreased with the addition of trace amounts of Ti,while the subcooled liquid region remained almost constant(ΔTx of approximately 50 K)and the relaxation enthalpy of the system gradually decreased.Compression and nanoindentation experiments show that the plasticity and strength of the amorphous alloy in the system increase and then decrease as the Ti content increases,reaching a maximum at Ti=2,with a yield strength of about 2100 MPa and a fracture strength of about 2200 MPa.In addition,the amorphous alloy of this composition exhibits work hardening after the yield point,which is responsible for its excellent mechanical properties.The other components in this system also exhibit a yield strength of approximately 2000 MPa and have some plasticity.The cross-sectional morphology of the amorphous alloy material shows relatively dense and uniform shear bands and striations for all components.Specifically,the striations are most dense and homogeneous when Ti=2,and the average spacing of the shear bands is small.Subsequent nanoindentation experiments showed that the addition of 1-3%elemental Ti increased the hardness of the system,with a maximum value of 677 HV for Ti3.However,the hardness of the system continued to decrease with further additions of elemental Ti.In addition,the modulus of elasticity decreased to varying degrees compared to components without Ti elements,with the lowest value of 96.1GPa for Ti2,which is closer to the properties of human bone than the current medical titanium alloy(Ti-6Al-4V)and medical stainless steel.Electrochemical polarization tests carried out in simulated body fluids at a constant temperature of 37℃ showed that the material has a high self-corrosion current density and a low self-corrosion voltage.However,all components of the system showed a wide passivation range in the simulated body fluid(SBF solution),indicating that the material formed a very dense and stable passivation film in the simulated body fluid,effectively preventing premature pitting behaviors.Subsequent XPS tests showed that the system produced ZrO2 and Al2O3 passivation films in the simulated bulk solution,which may be an important reason for the material’s excellent corrosion resistance.