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Wyświetlanie 1-7 z 7
Tytuł:
Precipitation Processes during Non-Isothermal Ageing of Fine-Grained 2024 Alloy
Autorzy:
Kozieł, J.
Błaż, L.
Włoch, G.
Sobota, J.
Lobry, P.
Powiązania:
https://bibliotekanauki.pl/articles/352499.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
AA2024 alloy
scrap metal milling
structure refining
powder metallurgy
precipitation hardening
Opis:
Mechanical alloying and powder metallurgy procedures were used to manufacture very fine-grained bulk material made from chips of the 2024 aluminum alloy. Studies of solution treatment and precipitation hardening of as-received material were based on differential scanning calorimetry (DSC) tests and TEM/STEM/EDX structural observations. Structural observations complemented by literature data lead to the conclusion that in the case of highly refined structure of commercial 2024 alloys prepared by severe plastic deformation, typical multi-step G-P-B →θ” →θ’ →θ precipitation mechanism accompanied with G-P-B →S” →S’ →S precipitation sequences result in skipping the formation of metastable phases and direct growth of the stable phases. Exothermic effects on DSC characteristics, which are reported for precipitation sequences in commercial materials, were found to be reduced with increased milling time. Moreover, prolonged milling of 2024 chips was found to shift the exothermic peak to lower temperature with respect to the material produced by means of common metallurgy methods. This effect was concluded to result from preferred heterogeneous nucleation of particles at subboundaries and grain boundaries, enhanced by the boundary diffusion in highly refined structures. Transmission electron microscopy and diffraction pattern analysis revealed the development of very fine Al4C3 particles that grow due to the chemical reaction between the Al matrix and graphite flakes introduced as a process control agent during the preliminary milling of chips. Al4C3 nano-particles are formed at high temperatures, i.e. during hot extrusion and the subsequent solution treatment of the samples. Highly refined insoluble particles such as aluminum carbide particles and aluminum oxides were found to retard recrystallization and reduce recovery processes during solution treatment of preliminarily milled materials. Therefore, the as-extruded material composed of a milled part and chip residuals retained its initial bimodal structure in spite of solution heat treatment procedures. This points to a high structural stability of the investigated materials, which is commonly required for new technologies of high-strength Al-based materials production.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 1; 169-176
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Silver Matrix Composite Reinforced by Aluminium-Silver Intermetallic Phases
Autorzy:
Wloch, G.
Skrzekut, T.
Sobota, J.
Woznicki, A.
Błaż, L.
Powiązania:
https://bibliotekanauki.pl/articles/352667.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
silver-aluminum composite
plastic consolidation
powder metallurgy
Ag-Al intermetallics
Opis:
Silver and aluminum powders (82 mass % Ag and 18 mass % Al) were mixed and hot extruded at 673 K with extrusion ratio λ = 25. Performed X-ray diffraction analysis of as extruded rod revealed the development of Ag3Al and Ag2Al-type intermetallic phases. Structural observations and both chemical and diffraction analysis of structural components confirmed the growth of mentioned phases in the vicinity of elementary Al and Ag granules. No pores or voids were observed in the material. Mechanical properties of the composite, UTS = 490MPa, YS = 440 MPa, HV2 = 136, were relatively high if compared to commercial Ag and Cu products. Hot compression tests pointed to the good hot workability of the composite at deformation temperature range 473 K - 773 K. The differential scanning calorimetry tests were performed in order to estimate structural processes during heating of Ag/Al composite that lead to thermodynamically stable liquid state. It was found that characteristic temperature of three endothermic peaks correspond to (1) peritectoid transformation μ-Ag3Al → ζ-Ag2Al + (Ag), (2) the eutectic melting ζ-Ag2Al + (Al) → L, (3) melting of the ζ-Ag2Al phase. The Vickers hardness of the samples annealed at 673 K, for the time range up to 6900 minutes, was also determined. It was concluded that mutual diffusion of elements between Ag and Al granules and the growth of μ-Ag3Al and ζ-Ag2Al grains during annealing at 673 K result in a slight hardening of the composite.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 1; 427-434
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The role of simulation-based training in neonatal cardiopulmonary resuscitation complicated by meconium aspiration syndrome
Autorzy:
Zych, B.
Błaż, W.
Muster, M.
Kraśnianin, E.
Wróbel, R.
Kremska, A.
Błajda, J.
Raba, G.
Powiązania:
https://bibliotekanauki.pl/articles/2087796.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Opolski. Instytut Nauk o Zdrowiu
Tematy:
newborns
simulation
meconium aspiration syndrome
cardiopulmonary resuscitation
education
midwives
Opis:
Background: The use of simulation-based training is strategic in training medical staff. Aim of the study: The aim of the study was to assess the knowledge and skills of performing neonatal CPR (cardiopulmonary resuscitation) complicated by the presence of meconium in the respiratory tract in two groups of midwives (trained in the traditional tutorial-based model vs simulation-based training) with an interactive neonatal manikin. Material and methods: The knowledge and practical skills assessment was conducted in two groups of midwives. The knowledge of the participants was assessed using both a written test consisting of 25 control questions (5 questions on meconium aspiration syndrome, 20 on neonatal CPR) and practical skills including 12 activities (1-initial, 9-proper, 2-final). The complex “success” indicator was determined based on the effects of patient resuscitation (15 minutes of the scenario), and the reference point for knowledge and skills was to obtain a minimum of 70% correct answers/activities performed, evaluated by three independent experts. Results: In the knowledge test, the respondents scored 17.93 ± 3.11 points out of 25 (71.7%). Practical skills for all respondents were 17.57 ± 2.49 points out of 21 (83.66%), with a tendency to obtain higher points in cleaning of the airways and stimulation of the newborn, and lower for ventilation and the use of an alternative method of intubation. Despite the similar level of practical skills in both groups, only a higher statistical tendency was observed in three out of nine instrumented “proper activities” in the simulation trained midwives. Conclusions: The scenario used by us assessing the knowledge and skills of midwives taught in traditional tutorial-based and simulation-based training, indicates the advantage of acquiring individual competences in a short time using simulation-based training. This increasingly popular scientific model allows the acquisition of “invasive” competencies, but it requires further research.
Źródło:
Medical Science Pulse; 2020, 14, 3; 25-30
2544-1558
2544-1620
Pojawia się w:
Medical Science Pulse
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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