Synthesis and Properties of High-Manganese Iron-Based Bulk Amorphous Metals as Non-Ferromagnetic Amorphous Steel Alloys
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Synthesis and Properties of High-Manganese Iron-Based Bulk Amorphous Metals as Non-Ferromagnetic Amorphous Steel Alloys S. Joseph Poon1, Gary J. Shiflet2, V. Ponnambalam1, Veerle M. Keppens3, R. Taylor3, G. Petculescu3. 1
Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA. Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904-4745, USA. 3 Department of Physics, The University of Mississippi, National Center for Physical Acoustics, Coliseum Drive, University, MS 38677, USA. 2
(Approved for Public Release. Distribution Unlimited) ABSTRACT High-manganese ferrous-based alloys containing 10-20 at. % Mn have been investigated as prospective iron-based structural amorphous metals with magnetic transition temperatures far below the ambient temperature. Many of these alloys are found to have a high reduced glass transition temperature of 0.6-0.63 and large supercooled liquid region of 40-90 oC. Rod-shaped amorphous samples with diameters reaching 4 mm are obtained by employing simple injection casting. The search for good glass-forming alloys has been guided by an atomistic approach coupled with the realization of low-lying liquidus temperatures via proper alloying. The tensile yield strengths and Vickers hardness of the new amorphous metals far exceed those known in high-strength steel alloys, and the elastic moduli are comparable to those reported for super-austenitic steels. The present highmanganese amorphous Fe-alloys also show promise as very good corrosion-resistant materials. INTRODUCTION Studies of bulk-solidifying iron-based amorphous metallic alloys (Fe-based bulk amorphous metals) to date are mainly focused on soft-magnetic applications [1-3]. These Fe-based bulk amorphous metals also exhibit specific strengths and Vickers hardness two to three times those of high-strength steel alloys; and in some cases, good corrosion-resistant properties are observed [4]. Fe-based bulk amorphous metals are multi-component systems that contain 50-70 atomic percent Fe as the major component. The remaining composition combines suitable mixtures of metalloids (more generally Group B elements) and other elements selected from Co, Ni, and Cr, and refractory as well as lanthanide (Ln) metals. Using the injection casting method, Fe-based bulk amorphous metals can often be obtained in the form of cylinder-shaped rods 1-3 mm in diameter, and for one particular alloy composition, sample diameter reaching ~5 mm has been mentioned [1]. Meanwhile, amorphous rods of diameters up to 4 mm obtained by quenching highly purified molten Fealloys in water has also been reported [2]. The good formability of Fe-based amorphous metals can be attributed to the high reduced glass transition temperature Trg (glass temperature Tg divided by liquidus temperature Tl in K) of ~0.6 to 0.63 and large
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supercooled liquid region ∆Tx (crystallization temperature minus glass temperature) of at least ~30 oC measured. Clearly, it is also an attractive idea to develop Fe
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