QUANTITATIVE MICROSTRUCTURE ANALYSIS OF DISPERSION STRENGTHENED Al-Al 4 C 3 MATERIAL BY EBSD TECHNIQUE

Abstract The main aim of the present work was described quantitative analysis of microstructure of by electron backscatter diffraction (EBSD) technique of dispersion strengthened Al-Al 4 C 3 material. It is a technique by which SEM can be used to evaluate the microstructure by crystallographic analysis based on the acquisition of diffraction patterns from bulk samples. Mechanical properties of dispersion strengthened materials depend on microstructural and substructural parameters, their changes at elevated temperatures and also on grain and subgrain matrix structures. From this point of view the most important microstructural parameters of matrix are size, shape, and misorientation of grains and subgrains and their annealing behaviour. Realized microstructure analyses of Al-Al 4 C 3 material were evaluated from two experimental specimens annealed at different temperatures and times. Obtained microstructures were evaluated and compared. Annealing process has influenced the grain size, shape and orientation of experimental material. Grains size and angle grain boundaries were evaluated from acquired crystal orientation maps

Superplastična deformacija Al-Al4C3 kompozita

Deformation of the Al-Al4C3 composites with different volume fraction of Al-Al4C3 phase was investigated at different temperatures (293 - 723 K) and different strain rates (2,5 * 10-5 s-1 do 1,0 * 10-1 s-1). At temperatures 673 - 723 K and at the highest strain rate of 1,0 * 10-1 s-1, a significant ductility increase was observed. TEM analysis suggests the onset of superplasticity may be the result of dynamic grain polygonization, grain slip and rotation, partial recrystallization and dislocation creep in the tested system, which is known as strain induced dynamic recovery. Increase of the volume fraction of secondary phase in the studied composite resulted in a shift from slip on grain boundaries controlled mechanism to the grain rotation controlled deformation mechanism.Istraživana je deformacija Al-Al4C3 kompozita različitog volumnog udjela Al-Al4C3 faze kod različitih temperatura (od 293 do 723 K) i brzina deformacije (od 2,5 * 10-5 s-1 do 1,0 * 10-1 s-1). Kod temperatura od 673 do 723 K i najviše brzine deformacije od 1,0 * 10-1 s-1 zapaženo je značajno povećanje kovkosti. TEM analiza ukazuje da početak superplastičnosti može biti rezultat dinamičke poligonizacije zrna, klizanja i rotacije zrna, djelomične rekristalizacije i puzanja dislokacija u istraživanom sustavu, što je poznato kao deformacijom inducirano dinamičko oporavljanje. Porast volumnog udjela sekundarne faze u istraživanom kompozitu rezultirao je promjenom kontrolnog mehanizma deformacije od klizanja po granicama zrna do rotacije zrna

Stvaranje ultrafino zrnate (UFZ) strukture i mehanička svojstva sa intenzivnom plastičnom deformacijom (IPD)

Commercial pure cooper (99,9% Cu) was deformed by equal channel angular pressing (ECAP) using up to 10 passes, route C. The evolution of microstructure and fracture character were observed by OM, SEM and TEM. The mean grain size decreased with increasing deformation, after 10 passes to 100 – 300 nm. TEM analysis suggested the possible nanostructure formation mechanism by the formation of cellular structure in grains, forming of subgrains and then forming of high angle nanograins with random orientation. Fractures of ECAP Cu material after 10 passes had transcrystalline ductile character with dimple morphology.Trgovački čisti bakar (99,9%) deformiran je kanalnim kutnim prešanjem (KKP) do 10 provlaka-putanje. C. Razvitak mikrostrukture i karakter loma praćeno je sa OM, SEM i TEM. Veličina zrna se smanjuje povećanjem deformacije poslije 10 provlaka na 100-300 nm. TEM analiza ukazuje mogućnost nastajanja mehanizma nanostrukture stvaranjem celularne strukture u zrnima, nastanak subzrna i zatim obrazovanje nanozrna pod visokim kutem sa slučajnom orjentacijom. Lomovi KKP Cu materijala poslije 10 provlaka imali su transkristalni duktilni karakter sa jamičastom morfologijom