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

LAVORATO GABRIEL,; GIORGO FIORE; A. CASTELLERO; MARCELLO BARICCO; JAVIER A. MOYA

Buenos Aires

Conferencia; At the Frontiers of Condensed Matter V; 2010

CNEA

Amorphous alloys with composition (at%) Fe48Cr15Mo14C15B6Gd2 (alloy A) and Fe48Cr15Mo14C15B6Y2 (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 by 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 of 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 slighlty different crystallization sequence was observed. Values of hardness (∼13 GPa) and Young modulus (∼180 GPa) were measured by nanoindentation for both the alloys. The role of Y and Gd addition in adverse casting conditions, such as air atmosphere, and the effect of the partial replacement of pure elements with commercial grade raw materials on the glass formation are discussed.