Preparation and characterization of Fe-based bulk metallic glasses in plate form

Abstract

Amorphous alloys with composition (at%) Fe 48 Cr 15 Mo 14 C 15 B 6 Gd 2 (alloy A) and Fe 48 Cr 15 Mo 14 C 15 B 6 Y 2 (alloy B) were prepared either using pure elements (A and B1) and a commercial AISI430 steel as a base material (B2). When prepared from pure elements both alloys (A and 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 air atmosphere. In the case of alloy B2, prepared using commercial grade raw materials, rods of 2 mm diameter were obtained.X-ray diffraction and scanning electron microscopy observations confirmed that an amorphous structure was obtained in all the as-cast samples. A minor fraction of crystalline phases (oxides and carbides) was detected on the as-cast surface. Differential scanning calorimetry measurements showed a glass transition temperature at 856 K for alloy A and 841 K for alloy B1, and an onset crystallization temperature of 887 K for alloy A and 885 K for alloy B1. In the case of alloy B2 a slightly different crystallization sequence was observed.Values of hardness ( 13 GPa) and the Young modulus ( 180 GPa) were measured by nanoinden-tation for both the alloys. The effects of adverse casting conditions (such as air atmosphere, non-conventional injection copper mold casting and partial replacement of pure elements with commercial grade raw materials) on the glass formation and properties of the alloy are discussed.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

“…The results from Fe-B 15 Gd 2 suggest that, with a further tuning of composition, it should be possible to design an alloy with more stable amorphous state. By reference to the Fe-B 6 Y 2 alloy reported by Ponnambalam et al 3 and the recent work by Lavorato et al 31, it seems that the key for the fine tuning of the alloy composition is to tailor the ratio of C and B. Based on this judgment, the alloy Fe-B 6 Gd 2 was made by replacing Y 2 with Gd 2 and retaining the ratio of C:B = 15:6.…”

“…the same structures for the 1 st , 2 nd and 3 rd atomic shells for the two alloys. Such identical structural information can only be obtained by using the PDF analyses on the data acquired from SXRD, which is impossible when lab-based XRD was used as in the work of Lavorato, et al 31 and that of Blink, et al 10 where much uncertainty remained on whether or not the cast plates31 and coatings10 made by them contained nanocrystalline phases. The combined SXRD and PDF analyses conclude that amorphous states can be achieved for both Fe-B 6 Gd 2 and Fe-B 6 Y 2 alloys up to Ø5.8 mm.…”

Quantification of Thermal Oxidation in Metallic Glass Powder using Ultra-small Angle X-ray Scattering

“…For example, Fe 48 Cr 15 Mo 14 Y 2 C 15 B 6 metallic glass exhibits exceptionally high elastic modulus of 200 GPa and compressive fracture strength of 3200 MPa. The hardness of this metallic glass is also high (13 GPa) 16–19 . Metallic glasses in the Fe-Si-B alloy system also possess excellent soft magnetic properties such as high permeability and low core loss.…”