K. M. MOSTAFA, N. Van Caenegem, Y. Houbaert, Gent University, Zwijnaarde, Belgium; J. De Baerdemaeker, D. Segers, Gent University, Gent, Belgium
The influence of the addition of C to the Fe-Mn-Si-Cr-N base material is investigated at room temperature. Steel samples were deformed during a tensile experiment up to a strain of 17 %. Light optical microscopy (OM) and XRD gave information about the different micro-structural phases that exists in the deformed and the undeformed alloys. The evolution of the defect structure is followed by positron annihilation techniques such as Doppler broadening of annihilation radiation spectroscopy (DBAR) and the positron annihilation lifetime spectroscopy (PALS). During deformation a martensitic e-phase is induced. The size of the martensite plates increases with increasing deformation
Summary: The influence of the addition of C to the Fe-Mn-Si-Cr-N base material is investigated at room temperature. Steel samples were deformed during a tensile experiment up to a strain of 17 %. The evolution of the defect structure is followed by positron annihilation techniques such as Doppler broadening of annihilation radiation spectroscopy (DBAR) and the positron annihilation lifetime spectroscopy (PALS).
From the results of the positron annihilation, the Doppler broadening parameter S increases as a result of the trapping of positrons in defects. In the early stages of deformation, no significant increases of the S parameters for both alloys are observed. The increase of S is caused by an increasing number of lattice defects (dislocations, vacancies). The starting of saturation of the S parameter corresponds to the trapping of most of the positrons by the lattice defects. Phase transition can be detected from the S-W relation. The carbon content in the alloys has a significant effect in the value of the S parameter, which means the concentration of defect.
