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Pawelek A.,Institute of Metallurgy and Materials Science | Piatkowski A.,Institute of Metallurgy and Materials Science | Wajda W.,Institute of Metallurgy and Materials Science | Skuza W.,Institute of Metallurgy and Materials Science | And 5 more authors.
Archives of Metallurgy and Materials | Year: 2016

The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres) as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect) and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical), TEM and SEM images. © 2016, Committee of Metallurgy. All rights reserved.

Ranachowski Z.,Polish Academy of Sciences | Jozwiak-Niedzwiedzka D.,Polish Academy of Sciences | Ranachowski P.,Polish Academy of Sciences | Dabrowski M.,Polish Academy of Sciences | And 2 more authors.
Brittle Matrix Composites 11 - Proceedings of the 11th International Symposium on Brittle Matrix Composites BMC 2015 | Year: 2015

In the paper a method of X-ray microtomography (micro-CT) was employed for a direct insight into a microstructure of concrete with a practical resolution of approx. 10 micrometers3. Two sets of specimens were subjects of examination. The spatial concentration of air pores was investigated in three concretes differing in the amount of the supplement of high calcium fly ash (HCFA). The parameter of pore connectivity called diffusive tortuosity was determined in three other concretes made of the same ingredients but differing in water to cement ratio. The quantitative results obtained with application of described procedures are applicable in material characterization.

Nagy S.,Institute of Materials and Machine Mechanics | Nagy S.,Slovak University of Technology in Bratislava | Nosko M.,Institute of Materials and Machine Mechanics | Orovcik L.,Institute of Materials and Machine Mechanics | And 4 more authors.
Materials and Design | Year: 2015

The work is focused to prepare Al based master-alloy pellet with 50vol.% of Al2O3 for subsequent manufacturing of aluminum matrix composites with desired amount of reinforcement (5-20%). Since master-alloy is manufactured via pressure infiltration and proper interface between particles and melt is required for uniform particle distribution within the melt, fundamental correlation between parameters of pressure infiltration and quality of the Al/Al2O3 interface is revealed in this study. Standard observation techniques as 3-D computed tomography (CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) are used for structural characterization. Drop test was used to estimate effect of time, temperature, annealing of Al2O3 and its type on the wettability of Al2O3 with Al. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to study changes within the Al2O3 prior infiltration. Stir casting was used to prepare the final composite and dynamical mechanical analysis (DMA) was used to estimate the Young's modulus of as-cast composite. The proper infiltration parameters was defined in this work and it were shown that the infiltration temperature and pressure have direct correlation on the interface between particle and aluminum. © 2014 Elsevier Ltd.

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