J. Phys. IV France
Volume 05, Numéro C8, Décembre 1995
International Conference on Martensitic Transformations – ICOMAT 95
Page(s) C8-361 - C8-366
International Conference on Martensitic Transformations

J. Phys. IV France 05 (1995) C8-361-C8-366

DOI: 10.1051/jp4:1995853

Significance of Rate of Work Hardening in Tempered Martensite Embrittlement

J. Pietikainen

Laboratory of Physical Metallurgy and Material Science, Helsinki University of Technology, 02150 Espoo, Finland

The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of work hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe3C appear in quite different tempering temperature ranges. The Ms temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of work hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of work hardening are considered.

© EDP Sciences 1995