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Enhanced Non-linear Viscoelastic Properties of Polymer Bonded Explosives Based on Graphene and a Neutral Polymeric Bonding Agent

Lin C., He G., Liu J., Pan L., Liu S.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 4

788--805

EN

During their long-term storage and transport, polymer bonded explosives (PBXs) will be subjected to complex thermal physical environments with combined thermal and mechanical loads. The creep behaviour results in a change of physical and mechanical properties, which consequently influences the explosive performance. In this work, graphene and a neutral polymeric bonding agent (NPBA) were selected to improve the non-linear creep properties of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based PBXs. The results were compared with the creep response of the corresponding PBXs without additives and with graphene alone. It was observed that graphene and an NPBA exhibited a positive effect, improving the creep resistance of TATB-based PBXs. The compressive and tensile strength of 0.5 wt.% graphene-filled PBXs were improved by 5.1% and 29.2%, respectively, compared to raw TATB-based PBXs without additives. The performance of the PBXs was further enhanced by the addition of 0.1 wt.% NPBA. For a given stress and temperature, the TATB-based PBXs with graphene and NPBA deformed significantly less than the PBXs filled with graphene alone.

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Mechanical properties and creep resistance of nickel alloys after complex modification and double filtration

Binczyk F., Gradoń P., Mańka M.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

5-8

EN

The paper presents the results of studies to determine the effect of complex surface and bulk modification and double filtration during mould pouring on the stereological parameters of macrostructure and mechanical properties of castings made from the post-production waste IN-713C and the MAR-247 nickel alloys. The evaluation covered the number of grains per 1mm2 of the sample surface area, the average area of grains and the shape index, hardness HB, tensile strength and resistance to high temperature creep. The results indicate the possibility of controlling the stereological parameters of macrostructure through application of several variants of the modification, controlling in this way also different low- and high-temperature properties. The positive effect of double filtration of the alloy during mould pouring on the metallurgical quality and mechanical properties of castings has also been emphasized.

3

Mikrostruktura i właściwości nowych martenzytycznych stali 12 % Cr dla nadkrytycznych bloków energetycznych

Zielińska-Lipiec A., Kozieł T., Czyrska-Filemonowicz A.

Hutnik, Wiadomości Hutnicze

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2009

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Vol. 76, nr 4

269-275

PL

Badaniom mikrostrukturalnym poddano martenzytyczną stal VM12 zawierającą 12 % chromu, opracowaną przez COST 522 dla elektrowni konwencjonalnych pracujących w temperaturze około 625÷650 °C. Analizowano mikrostrukturę stali w stanie dostawy, po długotrwałym (29 000 godz.) wyżarzaniu, jak i pełzaniu w temperaturze 625 °C. Ilościową analizę obrazu na elektronomikroskopowych zdjęciach mikrostruktury prowadzono w celu określenia gęstości dyslokacji wewnątrz listew martenzytu/podziarn, wielkości podziarn, jak i wielkości (średnia średnica) oraz kształtu (współczynnik kształtu) wydzieleń. Fazy wtórne identyfikowano przy wykorzystaniu selektywnej dyfrakcji elektronów. Badania za pomocą TEM wykazały, że zarówno długotrwałe wyżarzanie, jak i pełzanie w temperaturze 625 °C powoduje zmiany w mikrostrukturze. Ilościowa analiza parametrów mikrostruktury wykazała, że podczas długotrwałego (29 000 godz.) wyżarzania wielkość podziarn oraz węglików M23C6 rośnie. Dla stali odkształconej podczas pełzania zmiany w mikrostrukturze są bardziej zawansowane w porównaniu ze stalą jedynie wyżarzaną w tym samym czasie. W artykule dyskutowana jest ewolucja mikrostruktury i jej wpływ na długoczasową wytrzymałość na pełzanie stali VM12.

EN

The microstructure of the new COST martensitic 12 % chromium steel VM12 developed for advanced power stations operated around 625÷650 °C in the as received condition and after long-term creep exposure (up to around 29 000 h) has been investigated. Quantitative analyses of VM12 steel microstructure based on TEM micrographs were undertaken to determine the dislocations density within the subgrains, the width of the martensite laths/subgrains and the particles parameters (shape, size, distribution). Phases identification was performed using electron diffraction. The TEM results showed that the thermal exposure at 625 °C and creep deformation caused some changes of VM12 steel microstructure. The statistical quantitative analyzes of the microstructural parameters, showed that the size of subgrains and M23C6 precipitates slightly increased after exposure up to 29 000 h. In the creep tested specimens, microstructure changes were much more pronouced than in the thermal exposed specimens. Microstructural stability and its influence on the long-term rupture strength of the VM12 steel is discussed in the paper.