The use of nanotechnology to improve the bulk and surface properties of steel for structural applications - Nanotechnology in Eco-efficient Construction - page 80

Table 5.1 Recent research on the utilization of nanotechnology to improve the mechanical properties of steel bulk

Production
process

Microstructure of bulk
material

Novel properties or
phenomenon Reference Steel type Mechanism(s)

Kusinski and
Pollack (2008)

Carbon steel
( ≤ 0.35% C)

Heating into the
austenite range
+ cooling to
induce γ → α
and γ → α ′
transformations
+ rolling or
forging

Triple-phase: crystals
featuring parallel α ′
laths with nano- γ
fi lms in between,
fused with α
crystals (2-100 μ m)

High strength, toughness,
corrosion resistance,
and cold formability

Great toughness by
the lath structure;
ductility and
formability by the
retained- γ fi lms

Eskandari et al.
(2009)

301 SS TMT: repetitive

cold rolling +
annealing

90 vol% of nano-
crystal γ grains
(30-40 nm)

High yield strength (up to
2000 MPa)

Strain inducing the
formation of α ′
with lattice
defects, followed
by α ′→ γ reverse
transformation

Menapace et al.
(2009)

Fe-1.5%Mo
powder + SiC
(1.5 wt.%,
30 nm)
particles

Microalloying +
spark plasma
sintering

Multiphased
nanostructure with
'elongated (bainitic
α ) lamellae
separated by thin
layers of retained- γ ';
some equiaxed
α -grains and α ′

Yield strength of
550 MPa; uniform
plastic strain (10%) at
fracture (1020 MPa)

Transformation-
induced plasticity
(TRIP)

Guo et al. (2010) Nb-microalloyed

pipeline steel

Two-stage
thermo-
mechanical
rolling + fast
cooling

Mainly fi ne plate
domains ( ∼ 3.2 μ m)
featuring lath-
bainite ( ∼ 200 nm
thick) and some
acicular α

Yied strength of 900 MPa;
low yield ratio of 0.84;
El of 15%; impact
toughness of 200 J at
− 20°C

Nano-precipitates of
(Nb, Ti)(C,N) and
NbC to inhibit
grain growth; high
dislocation density
of microstructure