Thermally activated martensite formation in ferrous alloys

Abstract

Magnetometry was applied to investigate the formation of α/α´ martensite in 13 ferrous alloys during immersion in boiling nitrogen and during re-heating to room temperature at controlled heating rates in the range 0.0083–0.83Ks−1. Data shows that in 3 of the alloys, those that form {5 5 7}γ martensite, no martensite develops during cooling. For all investigated alloys, irrespective of the type of martensite forming, thermally activated martensite develops during heating. The activation energy for thermally activated martensite formation is in the range 8–27kJmol−1 and increases with the fraction of interstitial solutes in the alloy.