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Open AccessArticle

Gradient Nanostructured Tantalum by Thermal-Mechanical Ultrasonic Impact Energy

1
Department of Safety Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
2
Department of Mechanical Engineering, Sun Moon University, Asan 31460, Korea
*
Author to whom correspondence should be addressed.
Materials 2018, 11(3), 452; https://doi.org/10.3390/ma11030452
Received: 8 March 2018 / Revised: 15 March 2018 / Accepted: 19 March 2018 / Published: 20 March 2018
(This article belongs to the Special Issue Surface Modification to Improve Properties of Materials)
Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, which depends on the UNSM treatment temperature, via the surface severe plastic deformation (S2PD) method. The cross-sectional microstructure of the specimens was observed by electron backscattered diffraction (EBSD) in order to confirm the microstructural alteration in terms of effective depth and refined grain size. The surface hardness measurement results, including depth profile, revealed that the hardness of the UNSM-treated specimens at both temperatures was increased in comparison with those of the untreated ones. The increase in UNSM treatment temperature led to a further increase in hardness. Moreover, both the UNSM-treated specimens with an increased hardness resulted in a higher resistance to wear in comparison with those of the untreated ones under dry conditions. The increase in hardness and induced compressive residual stress that depend on the formation of severe plastically deformed layer with the refined nano-grains are responsible for the enhancement in wear resistance. The findings of this study may be implemented in response to various industries that are related to strength improvement and wear enhancement issues of Ta. View Full-Text
Keywords: tantalum; hardness; gradient nanostructured layer; grain size; residual stress; dry wear behavior tantalum; hardness; gradient nanostructured layer; grain size; residual stress; dry wear behavior
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MDPI and ACS Style

Chae, J.-M.; Lee, K.-O.; Amanov, A. Gradient Nanostructured Tantalum by Thermal-Mechanical Ultrasonic Impact Energy. Materials 2018, 11, 452.

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