Mechanical Properties And Corrosion Resistance Of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ Bulk Amorphous Alloy

Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ (at.%) bulk metallic glass(BMG) with a diameter of 5 mm was fabricated by copper mold casting. Its microstructure was examined by X-ray diffraction(XRD),Transmission electron microscopy(TEM),High resolution transmission electron microscopy (HRTEM). The mechanical properties and corrosion behaviors were investigated.It is confirmed that the as-prepared samples are fully amorphous in structure, and the HRTEM observations reveal atomic disorder and around 2 nm"mum-like"clusters in the Fe-based BMG alloys.Mechanical testing at room temperature shows that the Fe-based BMG of this study is brittle in nature. Gradients of hardness and micro-plasticity along the radius direction of the rodlike samples, due to different free volume fractions in the material caused by varying cooling rates, existed in Fe-based amorphous alloys. The phenomenon was explained by free volume model. The deformation behavior of the Fe-based BMG during nanoindentation involves two processes, i.e., elastic deformation with slight homogeneous plasticity and inhomogeneous plastic deformation. The dry friction resistance of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG is comparable to that of GCr15 steel.The results of immersion testing indicate that Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG shows good corrosion resistance in solutions of 1M HCl, 1 M H2SO4, 1 M HNO3, 1 M NaOH and 3.5% NaCl. Homogeneous pitting corrosion was observed occur slightly in 3.5% NaCl solution and relatively seriously in acid solutions. The electrochemical behavior of the Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG in 1 M HCl solution is superior to that of 1Cr18Ni9Ti, which is resulted from homogeneous structures and components distributed in the Fe-based BMG. The corrosion resistance of Fe-based BMG decreases with the increasing of concentration of HCl solutions. The enhanced cohesive ability of Cl- due to the increasing concentration of HCl solutions, combined with the disappearing of protective passive film due to the dissolve of Mo, leads to the easier contact between Cl- and the matrix of the BMG alloy, deteriorating the corrosion resistance of the amorphous alloys.