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Abstract

The morphology of G20Mn5 specimens made of non-modified and rare earth metals (REM) modified cast steel was investigated. Molten metal was treated with a cerium-rich mischmetal contain 49.8% Ce, 21.8% La, 17.1% Nd, 5.5% Pr and 5.35% other rare earth metals making up the balance. The melting, quenching (920°C/water) and tempering (720°C/air) were performed under industrial conditions. Analysis included G20Mn5 cast steel fracture specimens subjected to Charpy V-notch impact testing at 20°C, -30°C and -40°C. The purpose of the analysis was to determine the influence of REM on the microstructure and mechanical properties of G20Mn5 cast steel and the REM effect on the morphology, impact strength and character of the fracture surfaces. In addition, a description of the mechanism by which fracture occurred in the two materials was proposed. The author demonstrated the beneficial effects of adding REM to molten steel, manifested by a 20 - 40% increase in impact toughness, depending on test temperature, as compared to the non-modified cast steel. Important findings included more than 100% increase in impact strength in comparison with the required impact toughness of 27J at -40C for heat treated steels (EN 10213).

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Authors and Affiliations

Justyna Kasińska
ORCID: ORCID
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Abstract

Diesel engine components in the combustion chamber have been exposed to cyclic loadings under environmental effects, including high temperatures and corrosive fluids. Therefore, knowing the corrosion-fatigue behavior of materials is essential for designer engineers. In this article, pure fatigue and corrosion-fatigue behaviors of the piston aluminum alloy have been experimentally investigated. For such an objective, as-cast and pre-corrosive standard samples were tested by the rotary bending fatigue machine, under 4 stress levels. Some specimens were exposed to the corrosive fluid with 0.00235 % of the sulfuric acid for 100 and 200 hours. The results showed higher weight losses for 200 hours immersion times. As another result, it could be concluded that the lifetime decreased in pre-corrosive samples for both 100 and 200 hours of the immersion time, compared to that of as-cast specimens. However, such a lifetime reduction was more significant for 200 hours of the immersion time, especially within the high-cycle fatigue regime (or lower stress levels). Under high stress levels, both pre-corrosive sample types had almost similar behaviors. The field-emission scanning electron microscopy images of specimen fracture surfaces indicated that the brittle region of the fractured surface was larger for specimens after the 200 hours of corrosion-fatigue testing than the other specimen.
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Bibliography

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[10] Azadi, M., Bahmanabadi, H., Gruen, F. & Winter, G. (2020). Evaluation of tensile and low-cycle fatigue properties at elevated temperatures in piston aluminum-silicon alloys with and without nano-clay-particles and heat treatment. Materials Science and Engineering A. 788, 139497. DOI: https://doi.org/10.1016/j.msea.2020.139497.
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[14] Azadi, M. & Aroo, H. (2020). Temperature effect on creep and fracture behaviors of nano-SiO2-composite and alsi12cu3ni2mgfe aluminum alloy. International Journal of Engineering. 33(8), 1579-1589. DOI: 10.5829/ije. 2020.33.08b.16.
[15] Azadi, M. & Aroo, H. (2019). Creep properties and failure mechanisms of aluminum alloy and aluminum matrix silicon oxide nano-composite under working conditions in engine pistons. Material Research Express. 6, 115020. DOI: https://doi.org/10.1088/2053-1591/ab455f.
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Authors and Affiliations

M. Azadi
1
ORCID: ORCID
H. Aroo
1
M.. Azadi
1
M.S.A. Parast
1

  1. Semnan University, Iran
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Abstract

Results from anthropometric measurements and examinations of physical fitness of the candidates for the Polish Polar Expeditions from 1976 till 1980 are presented. The authors suggest the necessity of introducing fixed norms of physical fitness in medical qualification of the candidates for polar expeditions.

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Authors and Affiliations

Marek Kłossowski
Grażyna Łysoń-Wojciechowska
Krzysztof Kwarecki

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