Minor additions of Sn on bulk glass formation in a Fe-based system

Abstract

Minor additions of Sn in the bulk glass-forming Fe61−xSnxY2Zr8Co5Cr2Mo7B15 (x = 0% to 2%) system were studied in detail. It was found that combinations of Y and Sn can scavenge oxygen out of the undercooled liquids to form innocuous oxides, thus stabilizing the liquids. Besides this beneficial scavenging effect, Sn additions in the present Fe-based alloys also showed complex alloying effects on glass formation, which can be divided into three stages. At stage I (x 0.5%), the microalloyed compositions associate with the same eutectic as that of the base alloy. The glass-forming ability (GFA) of the resulting alloys is determined primarily by their liquidus temperature and similar to that of the base alloy. At stage II (0.85% x 1.15%), glass-matrix composite structures start to form because the alloy compositions are adjusted into a new “deeper” eutectic system. At stage III (x > 1.15%), however, alloy compositions shift to another new eutectic system, and the GFA is dramatically decreased due to the strong formation of primary phase –Fe. Homogeneous glass-matrix composites with a diameter of 7 mm in the alloy containing 1.0–1.15% Sn were successfully produced.