The use of nanotechnology to improve the bulk and surface properties of steel for structural applications - Nanotechnology in Eco-efficient Construction - page 85

Table 5.1 Continued

Production
process

Microstructure of bulk
material

Novel properties or
phenomenon Reference Steel type Mechanism(s)

Hidaka et al.
(2003)

Pure Fe and
cementite
(6.2% C)

SPD: mechanical
milling of
metallic
powder

Nano-crystal α grains
( ∼ 15 nm, for
Fe-0.8C)
transformed from
the dislocation cells

Dynamic continous
recrystallization

Added C facilitates
grain refi ning by
increasing the 'net
stored strain
energy' by
dislocations

Khodabakhshi
et al. (2010)

Low-carbon steel
(0.05-0.06% C)

SPD: constrained
groove
pressing

α grains (200-300 nm)
at cumulative grain
of 4.64

UTS of 450 MPa;
increased
superplasticity

Work hardening and
grain refi ning

Khodabakhshi
and
Kazeminezhad
(2010)

Electrical resistivity
improved by ∼ 100%

Refi ned
microstructure
and high density
of dislocations

Kozikowski et al.
(2010)

Eurofer 97 RAFM
steel

SPD: HE +
annealing

Heavily deformed
grains ( ∼ 80 nm)
after HE

Post-deformation
annealing at high
temperature improves
impact strength: 108 J/
cm 2 after 800°C/1h

Grain refi nement by
HE enhances TS
and
microhardness but
reduces ductility

Ahmadabadi et
al. (2011)

10Ni-7Mn steel SPD: cold rolling

+ equal-channel
angular
pressing

Ultrafi ne α grains
separated by
nano-NiMn
precipitate-
hardened pancake
grains

Substantially improved
tensile properties at
thickness reductions >
60%

Deformation-
induced α ′→ γ
reverse
transformation
and grain refi ning;
high % of high-
angle GBs and
saturated
vacancies