Deformation mechanisms in bulk nanostructured aluminum obtained after cryomilling and consolidation by spark plasma sintering

Bimodal bulk nanocristalline (nc)/ultrafine (UF) aluminum was produced after cryomilling and spark plasma sintering consolidation process. The samples obtainedwere plastically deformed in uniaxial compression. We show that there is a significant fraction of plastic strain (11%) that can be recovered after unloading. High-energy synchrotron X-ray diffraction experiments revealed that, there is a correlation between plastic strain recovery and microstructural evolution detected during in-situ loading-unloading experiments. Using a deconvolution approach, the nanostructured volume fraction (grain size below 100 nm) and the UF counterpart (grain size above 100-150 nm)were separated in terms of lattice strain, microstrain, crystallite size and crystallographic texture. During loading-unloading cycles we observe a lattice strain splitting between nc and UF volume fractions, a complete recovery of the peak broadening and a recovery of texture. These intriguing phenomena were explained to be strictly correlated with the lattice strain splitting behavior which act as the driving force for dislocation recombination

The study of ternary carbides formation during SPS consolidation process in the WC-Co-steel system

Tungsten carbide has a wide range of applications, mainly cemented carbides made of WC and Co, as wear resistant materials. However, the high cost of WC-Co powders encourages the use of a substrate to manufacture a functionally graded material (FGM) tool made of WC-Co and a tool steel. These materials join the high wear resistance of the cemented carbide and the toughness of the steel. This work deals with the study interaction of the WC-Co and H13 steel to design a functionally graded material by means of spark plasma sintering (SPS). The SPS, a novel sintering technique reaching the consolidation of the powders at relatively low temperatures and short dwell times, is a promising technique in processing materials. In this study, WC, H13 steel, WC-Co, WC-H13 steel and WC-Co-H13 steel bulk samples were investigated using scanning electron microscopy and X-ray diffraction techniques to evaluate the phase transformations involved during SPS consolidation process. The W(2)C and W(3)Fe(3)C precipitation were identified after the SPS consolidation of the WC and WC-H13 steel samples, respectively. The precipitation Of W(4)Co(2)C was also identified in the WC-Co and WC-Co-H13 steel samples. The WC-H 13 steel and WC-Co-H13 steel were also evaluated after heat treatments at 1100 degrees C for 9 h, which enhanced the chemical interaction and the precipitation of W(3)Fe(3)C and W(4)Co(2)C, respectively. (C) 2009 Elsevier Ltd. All rights reserved.CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)CNPq (National Counsel of Technological and Scientific Development