Fretting Fatigue Behavior of Amorphous Alloy in Simulated Body Fluid

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Fretting fatigue tests were carried out in a simulated body fluid using a Zr-based bulk amorphous alloy and its fretting fatigue behavior was studied. The fretting fatigue limits were compared with those of conventional metallic materials in air and in the simulated body fluid and the fretting fatigue crack nucleation mechanism was discussed using SEM observation of the fracture surfaces and XPS analysis of the fretted areas on the specimen surface. Corrosion behavior of Zr-based bulk amorphous alloys was also studied in various simulated body fluids.The results obtained are as follows.1) The tensile strength of a Zr-based bulk amorphous alloy was similar to that of pure Ti. However, the amorphous alloy exhibited the unique behavior that the fretting fatigue strength is higher in the simulated body fluid than that in air, while the fretting fatigue strength of Ti-6Al-4V was lower in the simulated body fluid than in air.2) The effect of environment on the fretting fatigue strength for t … More he Zr-based bulk amorphous alloy could be explained as follows. SEM observation showed that the morphology of the fretted area on the specimen surface was different between the specimens tested in air and in the simulated body fluid, and the fretting damage in the simulated body fluid was induced uniformly within the contact area of the fretting pad, while the damage in air was induced locally. Thus, the fretting damage induced locally in air introduced the stress concentration on the specimen surface and decreased the fretting fatigue strength. The difference between oxide films formed on the specimen surface in air and in the simulated body fluid seemed to affect the morphology of the fretting damage.3) We also studied the polarization behavior of a Zr based amorphous alloy in various simulated body fluids such as Hanks' solution and cell culture medium in order to examine the corrosion resistance in simulated body fluids. We found that the amorphous alloy has higher resistance to general corrosion and pitting corrosion in the fluids containing amino acid or protein.In addition, Zr based amorphous alloys have the lower Young's modulus of about 75 MPa, compared with that of conventional crystalline alloys and therefore, they are suitable for medical applications, if their plastic deformability at room temperature is improved. Less