Mechanical Behavior of Bulk Glassy Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5
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MECHANICAL BEHAVIOR OF BULK GLASSY Fe65.5Cr4Mo4Ga4P12C5B5.5 Mihai Stoica, Nicolle Radtke, Jürgen Eckert*, Stefan Roth, Germán Alcalá, Annett Gebert, Ludwig Schultz, Wei Hua Wang1, Yan Hui Zhao1 IFW Dresden, Institute for Metallic Materials, PO-Box 270016, D-01171 Dresden, Germany * present address: TU Darmstadt, Department of Materials and Earth Sciences, Physical Metallurgy Division, Petersenstrasse 23, D-64287 Darmstadt, Germany 1 Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, P. R. China ABSTRACT The bulk amorphous Fe-based alloy with the nominal composition Fe65.5Cr4Mo4Ga4P12C5B5.5 was obtained by copper mold casting in different shapes: cylindrical rods with diameters up to 2.5 mm and discs with 10 mm diameter and 1 mm thickness. This alloy exhibits good soft magnetic properties. Using electrochemical investigations we found that the corrosion resistance of this alloy is better than that of usual FeSi steel used for magnetic applications. Beside magnetic properties and corrosion resistance, this alloy exhibits also good mechanical properties. These were investigated by compression tests, nanoindentation and by an ultrasonic technique. The Young’s modulus E was found to be around 160 GPa, the yield strength σy is around 2.3 GPa and the fracture strength σf is around 3.23 GPa, together with an elastic strain εe = 1.5% and a fracture strain εf = 2.3%. The hardness was found to be around 10 GPa. INTRODUCTION Multicomponent alloys with high glass-forming ability and a wide supercooled liquid region, which is defined by the difference between the glass transition temperature Tg and the crystallization temperature Tx, give promise to expand the application field of amorphous ironbase alloys as soft magnetic materials [1]. Because of the absence of crystalline anisotropy, the Fe65.5Cr4Mo4Ga4P12C5B5.5 amorphous alloy exhibits good soft magnetic properties, characterized by a low coercive force and a high permeability [2]. Nevertheless, residual anisotropies may be present, such as shape anisotropy or stress-induced anisotropy, caused by internal mechanical stress induced during the preparation procedure [3, 4]. By annealing the samples at elevated temperatures, but below Tg, the unwanted anisotropies can be reduced. Furthermore, the lack of grain boundaries may result in enhanced corrosion resistance, which is expected to be beneficial for applications in aggressive environments. The investigated iron-based amorphous alloys with good corrosion resistance presented in the literature, like Fe-Cr-P-C [5], can be prepared only in ribbon form, due to their low glass-forming ability (GFA). Most recently, the effect of chromium on the glass formation and corrosion behavior of bulk glassy Fe-Cr-Mo-C-B alloys was described in [6]. Despite a large number of published papers, which describe the mechanical behavior of bulk amorphous alloys of the non-ferrous type, like Zr-, Ti-, Pd- or Cu- based alloys [7], for Febased bulk amorphous alloys obtained by copper mold casting only few experime
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