This study investigated the chloride-ion permeability of C30 concrete by adding bamboo fibers with different treatments (untreated, treated with calcium hydroxide solution and treated with sodium ...hydroxide solution) and different dosages. Three testing methods, namely the electric-flux method, AC test method and the RCM method, were used to characterize the concrete. Parameters such as electric-flux value, AC resistivity and chloride-ion diffusion coefficient were obtained. Results showed that the surface impurities of the bamboo fibers treated with calcium hydroxide solution were removed and the thermal stability of the bamboo fibers was improved, which can effectively enhance the chloride-ion permeability of concrete. Compared to untreated bamboo fibers, the improvement rate was between 14 % and 17 %. Sodium hydroxide is a strong alkaline solution, which can easily disrupt the structure of bamboo fibers and reduce the resistance of concrete to chloride-ion penetration. The best chloride-ion permeability was achieved when the bamboo fiber content reached 2 %. The electric-flux method, AC test method, and the RCM method were mutually validated with good correlation. It is recommended to choose a suitable and simple method for testing. Bamboo-fiber concrete lays a solid foundation for the future transformation of the civil-engineering industry.
Different cooling rates, such as room temperature water cooling (WQ), furnace cooling (FC), and water cooling + furnace cooling (FC +WQ), were introduced to study the effect on the solution-treated ...Mg-9Gd-4Y-2Zn-0.5Zr (w/%) alloy microstructure and mechanical properties. The grain size decreases as the cooling rate increases. With the lengthening of the cooling process time, the LPSO phase had enough time to nucleate and diffuse, the LPSO (long-period stacking order) phase filled the whole matrix crystal grains at the same time. In the process of furnace cooling and water cooling, the brightness of the LPSO phase was different, so it could be seen that the cooling rate would affect the contrast and morphology of the LPSO phase. The tensile yield strengths of the samples cooled with the furnace were better than those of the water-cooled samples, but their ultimate tensile strength and elongation to failure were poor. The fracture modes of the samples under different cooling rates were all subject to cleavage fracture, and the number and area of the cleavage planes and cleavage steps increased with the decrease of cooling speed, and the tearing area decreased, resulting in poor ultimate tensile strength and stretchability.
Celem artykułu jest prezentacja projektu mikrostruktury „Słownika polskiej terminologii prawosławnej”, realizowanego w ramach grantu Narodowego Programu Rozwoju Humanistyki (Moduł; dziedzictwo ...narodowe, I/2016). Autorzy przedstawiają schemat artykułu, obejmujący 10 segmentów: 1. Wyraz hasłowy, 2. Wymowa, 3. Warianty wyrazu hasłowego, 4. Odpowiedniki obcojęzyczne, 5. Kwalifikator, 6. Definicja, 7. Skrót, 8. Połączenia wyrazowe, 9. Synonimy, 10. Uwagi poprawnościowe. Następnie omawia się każdy z bloków, przedstawiając jego koncepcję, wybrane uzasadnienia, praktyczne rozwiązania i szczegółowe zasady zapisu danych.
A new method for the composite rolling of 304/Q345R was explored in the present study. The composite interface of the composite plate was studied using a scanning electron microscope (SEM) and ...electron-backscatter diffraction (EBSD). The results showed that a composite interface was formed with corrugated connections, increasing the length of the composite interface. Furthermore, the elongation of the corrugated interface relative to the original wave interface and the original horizontal interface were 29.43 % and 59.12 %, respectively. The composite interface became a 3D ripple interface from the traditional 2D plane. In the EBSD analysis, the strain energy at the interface of the corrugated composite interface was large, especially in the composite interface of the wave-waist position, indicating that the position of the ripple interface had a large deformation degree. This deformation is beneficial to the interface oxide and broken hardened layer conducive to the interface of the complex.
Łączenie materiałów róźnorodnych ma duże znaczenie w przemyśle lotniczym i nuklearnym. Wykonano połączenia różnorodne Inconel 625 – stal 17-4PH, Inconel 750 – stal 17-4PH metodą spawania plazmowego. ...Przeprowadzono badania mikrostruktury spoin za pomocą mikroskopu świetlnego i skaningowego, wykonano pomiary twardości w spoinie, strefie wpływu ciepła i materiale rodzimym. Badania wykazały, że metoda spawania plazmowego przy zastosowaniu odpowiednich parametrów spawania może być także stosowana przy otrzymywaniu połączeń różnorodnych stali 17-4PH ze stopami niklu. Microstructure of disimilar joints of 17-4PH steel and nickel alloys Abstract The joining of the dissimilar materials is very important in the aerospace and nuclear industry. The dissimilar joints of Inconel 625 – steel 17-4PH, Inconel 750 – steel 17-4PH were the plasma arc welded. The microstructure of the welds were studied using light microscopy and scanning electron microscopy. Hardness measurements of the weld, heat affected zone and base material were carried out. It was found that the plasma arc welding method using the suitable welding parameters may be also applied during the preparation of the dissimilar joints between 17-4PH steel and nickel alloys.
The aim of this experimental work was to design a modified test with which it will be possible to determine the fluidity of ductile cast iron. First, we planned the conceptual verification of the ...designed experiment, which was done by numerical simulations of the casting processes, followed by rapid mould fabrication using 3D printing. A measurement cell was placed in the mould cavity of the experimental chamber for further investigation of the cooling and solidification during casting. From the matrix of data obtained with the experiment, we defined the fluidity of the ductile iron EN-GJS-500-7. Also, we analysed the mechanical properties of the studied alloy, the microstructure, the chemical composition, and the results of the thermal analysis. In accordance with the expectations and theory from the literature, the fluidity in the experimental sample cast at a higher temperature was better than that cast at a lower temperature. Because of the faster cooling rate at the end of the channel of the experimental casting, the microstructure is fine, moreover, we obtain white solidification, ledeburite in the microstructure of the samples etched with Nital. At lower cooling rates, fewer graphite nodules appear in the microstructure, which are larger, and the portion of ferrite is greater.
Mury licowe podlegają ciągłym wpływom czynników pochodzących z otaczającego środowiska. Oddziaływania te przyczyniają się do destrukcji materiału, obniżając ich trwałość użytkową. Zaprawy należą do ...grupy materiałów aktywnych chemicznie, podlegającym korozji zewnętrznej i wewnętrznej. Do korozji zewnętrznej zalicza się wszystkie te przypadki, w których zaprawa narażona jest na niekorzystne czynniki zewnętrzne (gazowy CO2, kwaśne deszcze, zmienne temperatury przekraczające często punkt 0̊C, roztwory rozpuszczalnych soli mineralnych pochodzących z otaczających elementów). Przyczyną korozji wewnętrznej są same składniki zapraw. Wymienione czynniki istotnie wpływają na zmiany mikrostruktury zapraw. Proces ten jest rozłożony w czasie. Analizę przeprowadzono na stanowisku poligonowym zlokalizowanym na terenie Uniwersytetu Technologiczno – Przyrodniczego w Bydgoszczy. Do analizy wytypowano 3 mury licowe na różnych zaprawach. W kolejnych latach funkcjonowania murów obserwowano pojawianie się wykwitów o różnym zakresie i nasileniu. Zebrane informacje pozwoliły na ustalenie obszaru o najwyższej intensywności wykwitów. Po dziesięciu latach, dla każdego muru, z wytypowanego miejsca pobrano próbki zapraw, dla których zbadano mikrostrukturę metodą porozymetrii rtęciowej. Uzyskane wyniki posłużyły do oceny zmian udziału mezo- i makro-porów w badanych zaprawach powstałych w wyniku oddziaływania środowiska zewnętrznego.
The hot-deformation behavior of A356 aluminum alloy with a Sr modification was investigated using a Gleeble 1500 thermal simulator. The true stress-strain curves with a deformation temperature of ...300–500 °C and a strain rate of 0.01–5 s–1 were clarified. The activation energy of the A356 aluminum alloy with Sr modification was 221.474 kJ/mol. The influences of friction and temperature on the curves were investigated, and then the constitutive equation was established. The results show that the flow stress is obviously affected by temperature and strain rate. The experimental stress is lower than the theoretical stress, and the stress difference between the experimental and theoretical stress increases with the increasing strain. The maximum stress difference reaches 17.8 MPa when the sample deformed at 300 °C/5 s–1 with a reduction of 16 %. For all the deformation conditions the correlation coefficient is 0.99 and the average relative error is 4.8 %, which shows the good predictability of the current model. The developed constitutive equation can provide guidance for the study of the hot-deformation behavior of similar aluminum alloys.
A new refractory alloy, HfMoNbTiCr, was obtained by replacing Zr with Cr or Mo in the HfMoNbTiZr or HfNbTiCrZr alloys using vacuum arc melting. The phase components, microstructures and compressive ...properties of the alloy in the as-cast and annealed states were investigated. The results showed that the phase components changed from a single BCC phase in HfMoNbTiZr and BCC+Laves phases in HfNbTiCrZr to multiple phases – primarily two BCC phases and two cubic Laves phases – in HfMoNbTiCr. Notably, the yield and ultimate compressive strength of the as-cast alloy significantly increased from 1719 and 1803 MPa to 1851 and 2489 MPa, without a decrease in the ductility. The stress fields induced by Mo and the Cr-containing Laves phases were responsible for the enhanced strength, while the stiff network-like framework composed of intrinsically-strong Cr-containing Laves phases may have played a vital role in retaining the ductility.
Bulk metallic glasses are a new emerging field of materials with many desirable and unique properties, such as high strength, good hardness, good wear resistance, and high corrosion resistance that ...can be produced in near net shape components. These amorphous materials have many diverse applications from structural applications to biomedical implants. A complete overview of bulk metallic glasses is presented: the principles of alloy design, glass formation, processing, atomistic modeling, computer simulations, mechanical properties and microstructures.
PDF
