Thermoelectric materials Zr(Hf)NiSn(Sb) alloys were prepared by levitation melting followed by melt-spinning to refine the microstructure, and then consolidated by spark plasma sintering for the property measurements. XRD analysis showed that the half-Heusler phases were obtained. The microstructures of the melt spun thin ribbons were studied by the scanning electron microscope and transmission electron microscope. The thin ribbons were in the size of a few hundreds nanometers which didn't grow too much during the sintering process. Nanocrystals were found in the crystal grains. The carrier concentration increased for the melt-spinning samples compared with the levitation melting samples, indicating that the nanocrystals were metallic. The increasing boundary scattering after melt-spinning made the lattice thermal conductivity decrease

For the short-term creep behavior to be evaluated and the creep mechanism of P91 heat-resistant steels at low stresses and high temperatures to be clarified, stress-change testing was conducted with a "helicoidal-spring creep test" demonstrating a high strain resolution. The creep deformation consists of the primary creep stage, whereas no secondary creep stage was observed. Blackburn's law was suggested to be the best choice for a short-term-creep-behavior description because it provides a good representation of an experimental creep curve. An anelastic backflow at a low stress was confirmed, following a high reduction in the stress. The absolute value of the instantaneous strain for a load increase was equal to the value for a load decrease and the creep of the P91 steels at low stresses might have been controlled by the viscous glide of dislocations. Keywords: P91 heat-resistant steel, creep, anelastic, stress change Da bi bilo mo~oceniti kratkotrajno lezenje in njegov mehanizem toplotno obstojnega jekla P91 pri nizkih napetostih in visokih temperaturah, so bili izvedeni preizkusi spremembe napetosti z uporabo t.i. testa spiralne vzmeti, ki omogo~a veliko lo~ljivost deformacije. Deformacija lezenja sestoji iz primarne in sekundarne faze lezenja, vendar sekundarne faze niso analizirali oz. opazovali. Blackburnov zakon je najbolj uporaben zakon za opis obna{anja jekla med kratkotrajnim lezenjem, ker se z njim najbolj pribli`amo rezultatom, dobljenim z eksperimenti. Neelasti~ni povratni tok pri nizki napetosti je bil potrjen z ve~jim zmanj{anjem napetosti. Zaradi absolutne vrednosti trenutne deformacije za dano obremenitev je bil narastek deformacije enak zmanj{anju obremenitve, medtem ko je lezenje pri nizkih napetostih jekla P91 kontrolirano z viskoznim drsenjem dislokacij. Klju~ne besede: P91 jeklo za delo v vro~em, lezenje, neelasti~nost, sprememba napetosti