Preparation and Characterization of Fe-Based Metallic Glasses with Pure and Raw Elements

Amorphous alloys with a composition(at.%)Fe_(48)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) were prepared by using either pure elements(alloy B1)or a commercial AISI430 steel as a base material(B2).When prepared from pure elements,alloy(B1)could be cast in plate form with a fixed thickness of 2 mm and variable lengths between 10 and 20 mm by means of copper-mold injection in an air atmosphere.In the case of alloy B2,prepared by using commercial grade raw materials,rods of 2 mm diameter are obtained.Ribbons(B1 and B2)of width 5 mm and thickness about 30μm are prepared from the arc-melted ingots using a single roller melt spinner at a wheel speed of 40 m/s.The thermal and structural properties of the samples are measured by a combination of differential scanning calorimetry(DSC),x-ray diffraction and scanning electron microscopy.Chemical compositions are checked by energy dispersive spectroscopy analysis.X-ray diffraction and scanning electron microscopy observations confirm that an amorphous structure is obtained in all the samples.A minor fraction of crystalline phases(oxides and carbides)is detected on the as-cast surface.Values of hardness and Young modulus were measured by nanoindentation for both the alloys.The effects of adverse casting conditions(such as air atmosphere,non-conventional injection copper mold casting and the partial replacement of pure elements with commercial grade raw materials)on the glass formation and properties of the alloy are discussed.

Influence of Rare-Earth Substitution for Iron in FeCrMoCB Bulk Metallic Glasses

The effects of rare earth addition on the glass forming ability of Fe50-xCr15Mo14C15B6Mx （x =0, 2 and M=Y, Gd） bulks and ribbons are studied. The thermal and structural properties of the samples are measured by a combination of differential scanning calorimetry （DSC）, x-ray diffraction and scanning electron microscopy. Chemical compositions are checked by energy dispersive spectroscopy analysis. The copper mold casting technique leads to a fully amorphous structure up to 2mm only for compositions containing Y or Gd. In the case of ribbons, a fully amorphous phase is observed for all the compositions. The roles of Y and Gd are discussed on the basis of melting behavior analyzed by high-temperature DSC. Such elements act as oxygen scavengers, avoiding heterogeneous nucleation.

Crystallization Behavior of Fe_(50−x)Cr_(15)Mo_(14)C_(15)B_(6)M_(x)(x=0,2 and M=Y,Gd)Bulk Metallic Glasses and Ribbons by in situ High Temperature X-Ray Diffraction

The effect of rare earth addition on thermal stability of Fe_(50−x)Cr_(15)Mo_(14)C_(15)B_(6)M_(x)(x=0,2 and M=Y,Gd)is studied.Thermal and structural properties are measured using differential scanning calorimetry and x-ray diffraction,respectively.The microstructure is observed by using a scanning electron microscope,and chemical composition is checked by energy dispersive spectroscopy analysis.The effect of high temperature on the isothermal crystallization of Fe_(50−x)Cr_(15)Mo_(14)C_(15)B_(6)M_(x)(x=0,2 and M=Y,Gd)bulk metallic glass and ribbons is investigated by high-temperature x-ray diffraction.It is found that the crystallization behavior of Fe_(50−x)Cr_(15)Mo_(14)C_(15)B_(6)M_(x)(x=0,2 and M=Y,Gd)bulk metallic glass strongly depends on the annealing temperature.The different crystallization behavior is believed to be due to the different structures that the metallic glass possesses at different temperatures.