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  • Dislocation observations in duplex stainless steel using TEM
    Feizpour, Darja ...
    Samples of duplex stainles steel (DSS; 258 type) were isothermally annealed (aged) at temperatures of 300 °C and 350 °C for 10.000 h and 30.000 h. Thin foils of specimens were prepared using argon ... ion slicing or electrochemical thinning with finishing by jet-electropolishing method. Spinodal decomposition is expected to occur during thermal ageing of this type of materials. The characteristic is formation of nano-cellular microstructure of ferrite domains with regions enriched with Cr and other alloying elements. This causes significant change of mechanical properties (hardness and tensile strength increase, but ductility and toughness decrease). The change of mechanical properties must be related to the changes of material's internal structure (stacking faults, morphology and density of dislocations). Therefore, non-aged and aged samples were studied using transmission electron microscopy (TEM) at 200 kV electron accelerating voltage. It has been established that there is a lot of dislocations after ageing at 300 °C and that they appeared in different configurations with a lot of them being substantially mobile (numerous side-trails and traces of dislocations escape to the foil surface). The dislocation configurations changed and many of dislocations became immobilized (or at least slowed down in their movements) after ageing at 350 °C when the transformation of the matrix additionally occurred. The research enables to understand the characteristics of spinodal decomposition, the influence of ferrite presence in duplex stainless steel and thus help us to increase the life-time of components of thermal power plants made of DSS. Further investigations (TEM/EDS) will enable to explain the real rearrangement of alloying elements and formation of new phases during spinodal decomposition.
    Vir: Program in knjiga povzetkov = Program and book of abstracts (Str. 71)
    Vrsta gradiva - prispevek na konferenci
    Leto - 2010
    Jezik - angleški
    COBISS.SI-ID - 839594

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