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Abstract
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Outstanding mechanical properties of nanostructured carbide-free hard bainitic
steels, also known as super bainite, with microstructural constituents of less
than 100 nm thicknesses make them prone to be used in different engineering
applications. However, besides their exceptional strength and ductility combinations
during ordinary static or quasi-static deformation modes, it would be
also interesting to evaluate their mechanical behavior under high strain rate
deformation conditions. This article aims to investigate the mechanical performance
of nanostructured super bainite isothermally obtained at 300 Cby
applying both tensile and compressive high strain rate deformation modes.
Hopkinson compressive and tensile tests were performed up to the maximum
strain rate levels of 1.82 9 10
3
s
-1
and 1.040 9 10
4
s
-1
, respectively. Results
indicated that strength and ductility properties both significantly were dependent
on the strain rate values during tension and compression even if the effect
of tensile deformation mode was more considerable. The strength level
enhanced to almost 3000 MPa at the highest tensile deformation rate. According
to the results, the transformation-induced plasticity (TRIP) effect could not be
effective in ductility promotion at higher tensile strain rate deformations since
the austenite-to-martensite transformation did not take place gradually to pro-
duce a proficient transformation-induced plasticity effect. As a result, a premature
TRIP effect occurred and resulted in lower energy absorption during
deformation processes.
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