Wyniki wyszukiwania - BazTech

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In-Situ Observation of Acicular Ferrite Transformation in High-Strength Low-Alloy Steel Using Confocal Laser Scanning Microscopy

Lee Sang-In, Shin Seung-Hyeok, Park Hyeonwoo, Kim Hansoo, Lee Joonho, Hwang Byoungchul

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1497--1501

EN

In-situ observation of the transformation behavior of acicular ferrite in high-strength low-alloy steel using confocal laser scanning microscopy was discussed in terms of nucleation and growth. It is found that acicular ferrite nucleated at dislocations and slip bands in deformed austenite grains introduced by hot deformation in the non-recrystallization austenite region, and then proceeded to grow into an austenite grain boundary. According to an ex-situ EBSD analysis, acicular ferrite had an irregular shape morphology, finer grains with sub-grain boundaries, and higher strain values than those of polygonal ferrite. The fraction of acicular ferrite was affected by the deformation condition and increased with increasing the amount of hot deformation in the non-recrystallization austenite region.

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In-situ Observation of High-Temperature Fracture Behaviour of 347 Stainless Steel Subjected to Simulated Welding Process

Ko Seok-Woo, Park Hyeonwoo, Yoo Il, Kim Hansoo, Lee Joonho, Hwang Byoungchul

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

1019--1022

EN

In-situ study on the high-temperature fracture behaviour of 347 stainless steel was carried out by using a confocal laser scanning microscope (CLSM). The welding microstructures of the 347 stainless steel were simulated by subjecting the steel specimen to solution and aging treatments. Undissolved NbC carbides were present within grains after solution treatment, and M23C6 carbides were preferentially formed at grain boundaries after subsequent aging treatment. The M23C6 carbides formed at grain boundaries worked as stress concentration sites and thus generated larger cracks during high-temperature tensile testing. In addition, grain boundary embrittlement was found to be a dominant mechanism for the high-temperature fracture of the 347 stainless steel because vacancy diffusion in the Cr-depleted zones enhances intergranular fracture due to the precipitation of M23C6 carbides at grain boundaries.

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Wear Process Analysis of the Polytetrafluoroethylene/Kevlar Twill Fabric Based on the Components’ Distribution Characteristics

Gu D., Fan B., Li F., Yang Y., Chen S.

Autex Research Journal

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2017

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Vol. 17, no. 4

295--302

EN

Polytetrafluoroethylene (PTFE)/Kevlar fabric or fabric composites with excellent tribological properties have been considered as important materials used in bearings and bushing, for years. The components’ (PTFE, Kevlar, and the gap between PTFE and Kevlar) distribution of the PTFE/Kevlar fabric is uneven due to the textile structure controlling the wear process and behavior. The components’ area ratio on the worn surface varying with the wear depth was analyzed not only by the wear experiment, but also by the theoretical calculations with our previous wear geometry model. The wear process and behavior of the PTFE/Kevlar twill fabric were investigated under dry sliding conditions against AISI 1045 steel by using a ring-on-plate tribometer. The morphologies of the worn surface were observed by the confocal laser scanning microscopy (CLSM). The wear process of the PTFE/Kevlar twill fabric was divided into five layers according to the distribution characteristics of Kevlar. It showed that the friction coefficients and wear rates changed with the wear depth, the order of the antiwear performance of the previous three layers was Layer III>Layer II>Layer I due to the area ratio variation of PTFE and Kevlar with the wear depth.

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Influence of sintering temperature on morphology of dense bioceramics based on hydroxyapatite derived from porcine bones

Janus A. M., Major R., Faryna M.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 3

767-769

EN

Hydroxyapatite (Ca10(PO4)6(OH)2) is a major constituent of the mineral phase of human bones. It is considered as an attractive material for filling the bone defects. Synthetic hydroxyapatites and hydroxyapatites derived from the bovine bones and corals have been successfully commercialized. Hydroxyapatite coming from porcine bones seems to be an attractive field of research because there are still opened questions associated with its proper biological interaction, due to which it has not been commercialized yet. A procedure for the hydroxyapatite preparation from porcine bones was presented in the work. The presented results deal with morphological characterization of powders and bioceramics as well as in vitro biocompatibility investigations.

PL

Hydroksyapatyt (Ca10(PO4)6(OH)2) jest głównym składnikiem mineralnej części kości ludzkich. Jest uważany za atrakcyjny materiał do wypełnienia ubytków kostnych. Do tej pory udało się skomercjalizować hydroksyapatyty syntetyczne oraz otrzymywane z takich surowców naturalnych, jak kości wołowe oraz korale. Hydroksyapatyt otrzymywany z kości wieprzowych stanowi atrakcyjny kierunek badań, gdyż ten materiał nie został jeszcze skomercjalizowany. Przedstawiono sposób otrzymywania hydroksyapatytu z kości wieprzowych oraz wytwarzania z niego gęstej ceramiki. Zaprezentowano wyniki charakteryzacji morfologicznej proszków oraz ceramiki hydroksyapatytowej. Przedstawiono wyniki badań biokompatybilności in vitro wybranych odmian gęstej ceramiki hydroksyapatytowej.