Reverse α–α´ phase separation in Fe-20Cr-6Al alloy

Abstract

The reverse α–α′ phase separation in Fe-20Cr-6Al alloys has been monitored by differential scanning calorimetry in as-hot rolled and recrystallized samples previously aged at 435 °C. The splitting in the position of the minima, and the increasing enthalpy change involved, might be explained in terms of dissolution of α′ particles with different compositions and volume fractions. These results are fully consistent with the α–α′ phase separation kinetics determined by atom probe tomography during ageing at 435 °C. The monitoring of activation energy for α′ dissolution indicates that it is faster in as-hot rolled samples. Finally, the activation energy evolution indicates that there is first a dissolution of β′ Fe(AlTi) phase followed by α′ dissolution.

Keywords:

• differential scanning calorimetry (DSC)
• phase separation
• ferrous alloy
• mechanical alloying
• tomography

Acknowledgements

PM 2000^TM is a trademark of Plansee GmbH. LEAP® is a registered trademark of Cameca Instruments. Authors acknowledge financial support to Spanish Ministerio de Ciencia e Innovación in the form of a Coordinate Project in the Energy Area of Plan Nacional 2009 (ENE2009-13766-C04-01). G. Pimentel acknowledges MICINN for supporting her research under a FPI Grant. Research supported by ORNL’s Shared Research Equipment (ShaRE) User Facility, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.