Publication
Title
Globular structure of M2 high speed steel by thermomechanical treatment in the semisolid state
Author
Abstract
The globular structure of M2 high speed steel in the rolled - annealed and as cast conditions was investigated in the semisolid state. Metallographic observations resulted in globular austenite particles that were surrounded by a liquid phase. Dissolution of various carbides in the austenite phase at semisolid temperatures led to grain boundary liquation and formation of near-spherical solid grains in a liquid matrix. Therefore, at the semisolid state, the solid particles were free from carbides. MC- type and M6C- type eutectic carbides re- precipitated at the grain boundaries during cooling of the samples from the semisolid temperature. The variation of shape factor versus holding time and holding temperature was examined. A transition value for shape factor changes in high speed steels was achieved. The growth rate constants of the Ostwald ripening and the coalescence mechanisms were calculated by using the experimentally determined rate constant. It was observed that less liquid droplets were enclosed inside the solid particles compared with non-ferrous alloys. Besides, it has been shown that at high solid fraction, the Ostwald ripening mechanism plays a prominent role in the coarsening phenomenon in comparison with the coalescence mechanism. Grains can rotate and arrange low misorientation with each other at high liquid contents, therefore low energetic grain boundaries form between these grains. These grain boundaries play an important role in the coalescence mechanism.
Language
English
Source (journal)
Steel research international. - Düsseldorf
Publication
Düsseldorf : Verlag Stahleisen, 2010
ISSN
1611-3683
Volume/pages
81:5(2010), p. 381-386
ISI
000278292200007
Full text (Publisher's DOI)
UAntwerpen
Faculty/Department
Research group
Publication type
Subject
External links
Web of Science
Record
Identification
Creation 09.01.2015
Last edited 21.06.2017