Existing oxide dispersion strengthened (ODS) alloys are, besides Ni-based superalloy single crystals, the most creep-resistant materials. The creep resistance of the ODS alloys may, moreover, be significantly improved thanks to increasing the volume fraction of the nano oxides by more than one order of magnitude so that the oxides play a decisive role in strengthening. The present experimental study deals with two systems of such a high-volume fraction of nano oxides, namely, the Fe-11Al-1O and Fe-17Cr-7Al-4Y 2 O 3 systems prepared by mechanical alloying and hot rolling leading to a rather stable fine-grained microstructure. This microstructure undergoes static recrystallization at high temperatures. The kinetics of static recrystallization and coarsening of nano oxides in recrystallized grains is determined for both systems. The difference in kinetics of coarsening of Al-based and Y-based oxides in the Fe-11Al-1O and Fe-17Cr-7Al-4Y 2 O 3 systems is expressive and predetermines the Fe-17Cr-7Al-4Y 2 O 3 system or similar ones to become the new leading system among creep-and oxidation-resistant materials for applications up to 1200 • C. fraction of even finer sizes of oxides. Then, however, one cannot expect the resistivity of oxides against coarsening at very high temperatures. ODS alloys are produced in two steps: nano-composite powder from the matrix of the respective chemical composition and Y 2 O 3 is produced by mechanical alloying (MA), which is then hot consolidated in the second step. The recent commercially produced ODS alloys are represented by MA956 or MA957 [4], PM 2000 or PM 2010 [5], ODM alloys [6], 1DK or 1DS [7]. The non-commercially produced, experimental and advanced versions of ODS alloys are ODS Eurofer [8], 12YWT [9], 14YWT [10] and 9YWT [11]. New research on 14YWT [12] showed that mechanical properties of ODS alloys can significantly be improved via optimized processing consisting of a controlled thermo-mechanical treatment and in lowering content of N and C introduced during MA. Both steps led to a significant increase in fracture toughness attributed to improved cohesion of grain boundaries. However, processing of 14YWT is still extremely demanding [12].The excellent creep properties of the ODS alloys are explained by an attractive interaction of dislocations with oxides modeled by Rösler and Arzt [13], who predicted a threshold stress for creep decreasing with coarsening of oxides. A more detailed discrete dislocation model treating the collective interaction of precipitates with dislocations during creep has been published very recently [14]. A model for coarsening in multicomponent systems [15] shows that coarsening kinetics is proportional to the product of the solubility and the diffusion coefficient of O in the matrix. The solubility of O is determined by the chemical stability of the oxide (yttria is reported as the chemically most stable oxide) and a significant resistance against coarsening was confirmed by Krautwasser et al. [16] for yttria particles. The creep properties of ODS a...

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The application of innovative processing techniques to conventional raw materials can lead to new structural materials with specific mechanical and physical properties, which open up new possibilities of use in some areas of industry. The processing is enabled by powder metallurgy, which utilizes powders consisting of a metal matrix with dispersed stable particles achieved by mechanical alloying and their hot consolidation by rolling. New oxide dispersion strengthened (ODS) Fe-Al-based alloys are tested under different single and multiple thermomechanical treatments at different temperatures. The results show that new ODS alloys are significantly affected by the thermo-mechanical treatment, leading to microstructural changes. Their analysis is performed using different analytical methods such as optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Keywords: ODS alloys, composite, steel, Fe-Al Uporaba inovativnih tehnik preoblikovanja na obi~ajnih materialih lahko privede do novih konstrukcijskih materialov s specifi~nimi mehanskimi in fizikalnimi lastnostmi, ki odpirajo nove mo`nosti uporabe v industriji. Metalurgija prahov omogo~a uporabo prahov s kovinsko osnovo z dispergiranimi stabilnimi delci, ki jih dobimo pri mehanskem legiranju in vro~i konsolidaciji z valjanjem. Nove zlitine Fe-Al, disperzijsko utrjene z oksidi (ODS), so bile preizku{ene pri razli~ni, eno-ali ve~stopenjski obdelavi pri razli~nih temperaturah. Rezultati ka`ejo, da ima termomehanska obdelava novih ODS zlitin mo~an vpliv, ki se vidi v spremembah mikrostrukture. Analiza je bila izvedena s pomo~jo razli~nih analitskih metod, kot so: svetlobna mikroskopija, vrsti~na elektronska mikroskopija in rentgenska difrakcijska analiza.

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The specific mechanical property and structure of a material can be achieved by combining various types of materials and technologies. The main aim of this research is to develop new creep-and oxidation-resistant materials (ODS) (new ODS Fe-Al based alloys and ODS composites) applicable at high temperatures of up to about 1100°C. The new ODS composites consist of a ferritic Fe-Al matrix strengthened with about volume fractions 2 % to 30 % of Al2O3 particles. In order to find the optimum material structure, different oxide amounts were added to three different containers. Also, to find the influence of the temperature on the obtained structures, three processing temperatures of (26, 750 and 1150)°C were used with the specific deformation profile. An analysis of the structures was performed using different analytical methods such as light microscopy, scanning electron microscopy and X-ray diffraction analysis. Keywords: ODS steel, alloys, composite, creep, Fe-Al Posebne mehanske lastnosti in strukturo materiala je mogo~e dose~i s kombinacijo razli~nih vrst materialov in tehnologij. Glavni namen tega~lanka je razviti nov material, odporen proti lezenju in oksidaciji (ODS), tj. novo ODS-zlitino na osnovi Fe-Al in ODS-kompozite, uporabne pri visokih temperaturah do 1100°C. Novi ODS-kompozit je sestavljen iz feritne Fe-Al-osnove, oja~ane z okrog volumenskim dele`em od 2 % do 30 % delcev Al2O3. Da bi dobili optimalno strukturo materiala, je bil v tri vsebnike prime{an razli~en dele`oksida. Za ugotovitev vpliva temperature na dobljeno strukturo so bile uporabljene tri temperature izdelave (26, 750 in 1150)°C s posebnim profilom deformacije. Analiza strukture je bila izvr{ena z razli~nimi metodami, kot so svetlobna mikroskopija, vrsti~na elektronska mikroskopija in rentgenska difrakcija.