INFLUENCE OF COMPOSITION AND THERMAL HISTORY ON THE DYNAMIC RECRYSTALLIZATION AND SUBSEQUENT HOT DUCTILITY OF MILD STEELS

Citation
Le. Cepeda et al., INFLUENCE OF COMPOSITION AND THERMAL HISTORY ON THE DYNAMIC RECRYSTALLIZATION AND SUBSEQUENT HOT DUCTILITY OF MILD STEELS, ISIJ international, 33(7), 1993, pp. 799-806
Citations number
30
Categorie Soggetti
Metallurgy & Mining
Journal title
ISSN journal
09151559
Volume
33
Issue
7
Year of publication
1993
Pages
799 - 806
Database
ISI
SICI code
0915-1559(1993)33:7<799:IOCATH>2.0.ZU;2-3
Abstract
Torsion tests at strain rates of 1 x 10(-3), 1.6 x 10(-1) and 1 s-1 an d at temperatures between 850 and 1 100-degrees-C were carried out (1) on Al and Al-Ti mild steels after heating directly to the testing tem perature, (2) on Al steel soaking for 30 min at 1 200-degrees-C, then cooling the specimen to the testing temperature and (3) after soaking, cooling to 700-degrees-C and then heating to the testing temperature. Both steels showed a clear trough in ductility between 850 and 1 050- degrees-C, the ductility being lowest for the directly heated Al treat ed steel and the soaked, cooled below A1 and heated again, highest for the 1 200-degrees-C soaked steel and intermediate for the directly he ated Al-Ti steel. The lowest ductilities are associated with the inhib iting effect of AlN and TiN exerted on grain boundary migration and pr eventing the completion of dynamic recrystallisation, as shown also by their effect of increasing the peak strain and making the reaching of equilibrium dynamic recrystallised grain size difficult, which would markedly improve ductility. Soaking at 1 200-degrees-C, by dissolving and/or coarsening the AlN precipitates has the marked effect of increa sing ductility. The present results can be explained in terms of the d rag exerted by the dispersed particles making dynamic recrystallisatio n and grain growth difficult.