The use of nanotechnology to improve the bulk and surface properties of steel for structural applications - Nanotechnology in Eco-efficient Construction - page 81

Table 5.1 Continued

Production
process

Microstructure of bulk
material

Novel properties or
phenomenon Reference Steel type Mechanism(s)

Du et al. (2010) Microalloyed

steels

Warm-rolling + Uniform and

equiaxed

'Deformation-induced
transformation of
ultrafi ne austenite
(

Nucleation of α

deforming + grains

(100-300 nm)

α along GBs,

enhanced by the
boundary slipping

γ

quenching
(repetitive) ∼ 1 μ m) to ferrite'

Askari et al.
(2010)

High-strength
α

Microalloying Dual precipitate

microstructure: TiC
(avg. 10 nm) in the
matrix and coarse
cubic M 23 C 6 at GBs
and inside grains

Yield strength 2-3 times
higher than
'conventional
Ti-bearing high-
strength hot-rolled
sheet steels'

Nano-precipitates
destroy the
dislocations or
anchor against
their movement

-steel (0.08%
Ti)

Wang et al.
(2011)

High-strength
low-alloy steel
(low C, low Ti)

Microalloying Polyganal and

granular bainite, a
small amount of
α ′

Yield strength 640 MPa Strengthening effect

of nano-scale Fe 3 C
precipitates

+ α

hot rolling

islands, and
very small amounts
of fi ne pearlite

-

α

Hodgson et al.
(2011)

0.79C-1.5Si-
1.98Mn-0.98Cr-
0.24Mo-1.06Al-
1.58Co steel

200°C/10 days Bainitic laths

(average thickness
of 60

Excellent strength-
toughness-ductility
balance

Dual microstructure
that contributes to
ultrahigh strength
and toughness (by
nanobainitic laths)
as well as ductility
(retained

α

10 nm) with
retained-

±

fi lms in
between and high
dislocation density
(

γ

4.7 10 15 m -2 ) )

∼ × γ