Melt-spinning and semi-solid processing of bainitic steel

Abstract

A steel with a chemical composition meant to form nanostructured bainite following appropriate heat treatment, was, cooled rapidly from the liquid phase (1550°C) using melt spinning and modified injection-suction methods, as well as from a semi-solid temperature (1430°C) through thixoforming. The hardness of the as-cast melt spun ribbons was ∼960 HV due to a fine martensite–austenite mixture surrounded by three-dimensional skeleton-like primary carbides of length scale 0.2–0.3 µm. The suction-injection cast method led to a similar structure but less hard (780 HV) due to a lower cooling rate. The thixoformed material showed unmelted globular, fine grains and a fine eutectic mixture formed directly from the liquid phase. The variety of processed steel samples were tempered and their microstructures, examined.