Fabrication, Structure And Properties Of Fe-based Thin Film Metallic Glasses

Bulk Metallic glasses(BMGs) have emerged as a promising new metallic materials due to their high strength and hardness, good elasticity, excellent wear- and corrosion-resistance. However, MGs exhibit poor room temperature ductility(<2%) and small product size stemming from the limited glass forming ability, which strictly hinders their applications. Therefore, fabrication of thin film metallic glass(TFMGs) is thought to be an alternate route to overcome these shortcomings of MGs.A newly developed Fe-based MG alloy with a composition of Fe48Mo14Cr15Y2C15B6 have been fabricated by magnetron sputtering deposition using single alloy target. The preparation, microstructure and properties, including corrosion resistance, friction/wear properties of Fe-based amorphous thin films have been systematically investiga ted by means of X-ray diffraction(XRD), and scanning electron microscopy(FSEM), transmission electron microscopy(TEM), nano- indentation, Rockwell micro-hardness measurement, friction/wear testing system and electrochemical workstation.The optimized parameters were obtained by conducting a set of magnetron sputtering experiments according to the microstructure, deposition rate, adhesion properties, nano-hardness and modulus of the thin films obtained. The optimal sputtering parameters were described as following: working pressure, 0.7 Pa; sputtering powder, 120 W; sputtering time, 30 min. TFMGs prepared using the above parameters had fully single-phase amorphous structure, the highest deposition rate of 24.76±0.12 nm/min and a high nano-hardness of 12 GPa.The quantitative adhesion of the sample was measured by scratch tests. The critical load(Lc) for cracking of Fe-based TFMG is Around 90 mN. Results of dry friction and wear tests against Si3N4 demonstrate that the Fe-based TFMGs had lower friction coefficient(0.3~0.8) and nearly three times higher wear resistance(8.4×10-4 mm3 N-1m-1) with respective to 304SS(2.6×10-3 mm3 N-1m-1). The oxidation wear was the dominating mechanisms for Fe-based TFMGs during the wear process owing to a few oxygen-affinitive metals such as Fe, Cr and Mo involved in this al oy system.The corrosion properties of as-deposited TFMGs were evaluated by electrochemicalmeasurements in an artificial sweat solution, both potentiodynamic and potentiostatic tests performed in artificial sweat solution, showed that the Fe-based TFMG had better passivity and high pitting corrosion resistance than 304 SS. Mott-Schottky measurements revealed both n-type semiconducting character of passive films form on the two materials, while the TFMG exhibited significantly lower defect density and higher film thickness in its passive film, thus showing better corrosion resistance. The corrosion mechanism of TFMGs was composed of a serial of pitting processes, i.e., pitting initiation, metastable pitting growth, stable pitting and film rupture.