Grain boundary misorientation and positron annihilation characteristics in steel Eurofer processed by equal channel angular pressing Articles uri icon

publication date

  • October 2014

start page

  • 6722

end page

  • 6733

issue

  • 19

volume

  • 49

international standard serial number (ISSN)

  • 0022-2461

electronic international standard serial number (EISSN)

  • 1573-4803

abstract

  • Electron back-scattered diffraction and positron annihilation lifetime measurements were performed on the ferritic-martensitic 9 %Cr Eurofer steel processed by equal channel angular pressing (ECAP) at 550 A degrees C. The orientation imaging mapping images reveal ECAP-induced changes toward a more stable texture via rotation around aOE (c) 111 > and aOE (c) 110 > axes. These are accompanied by transformation of martensite into ferrite and a remarkable change in the bimodal distribution of grain misorientations with reduction of the fraction of high-angle grain boundaries. The positron annihilation measurements evidence the release of vacancies retained in the ECAP-processed material and their clustering into nanovoids in samples heat treated at T a parts per thousand yen 500 A degrees C. It is found that tensile strain applied at 600 A degrees C can inhibit this void formation in the ECAP-deformed material for 1 and 2 passes, but not in the case of 4 passes. A model for accounting the results is proposed.

keywords

  • radiation-induced segregation; stainless-steel; creep-behavior; single-crystals; iron; ods; microstructure; deformation; texture; alloy