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

Abstract

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 2mm and variable lengths between 10 and 20mm by means of copper-mold injection in air atmosphere. In the case of alloy B2, prepared using commercial grade raw materials, rods of 2mm 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 856K for alloy A and 841K for alloy B1, and an onset crystallization temperature of 887K for alloy A and 885K for alloy B1. In the case of alloy B2 a slightly different crystallization sequence was observed.Values of hardness (∼13GPa) and the Young modulus (∼180GPa) 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 partial replacement of pure elements with commercial grade raw materials) on the glass formation and properties of the alloy are discussed.