Study of microstructural dynamical changes in temperes steels at low temperatures by mechanical spectroscopy

Abstract

The mechanical spectroscopy is a technique of characterization with high sensibility to the micro- structural changes, especially to the phase transformati ons and the movement of disl ocations. This work studies the precipitation of epsilon carbide and the behavior of the dislocations during the transition from epsilon car- bide to cementite of a steel quenched and tempered by mechanical spectroscopy. The steel containing 0.71wt% was heated at 1093K for 5 minutes and cooled into wa ter. Then, the quenched samples were tempered for 10 minutes at 340, 380, 420 and 460K. Additionally, other sa mples were tempered at 380K for 1 and 20 hours. The increase of the intensity of temperi ng reduces the tetragonality of martens ite and the dislocation density. Inter- nal friction spectrum is decomposed into four peaks: P1 at 350K, P2 at 380K, P3 at 430K and P4 at 480K. P1 is attributed to the Snoek effect and this peak only appears in the sample tempered at 380K for 20 hours. P2 is reated to the precipitation of epsilon carbide. P3 and P4 are related to the interactions of dislocations with epsilon carbide and cementite, respectively.