Biomedical Engineering Reference
In-Depth Information
σ
0.2
= 0.14 + 4.8 N
2/3
[GPa]
(6.1)
When the nitrogen content is constant, the Hall-Petch equation
involves grain size
d
and
σ
y
yield strength with the following
dependence:
σ
y
=
K
d
-1/2
(6.2)
where
K
is constant.
K
value increases with increasing nitrogen
content (as shown in Fig. 6.5) [25].
Figure 6.5
Dependence of Hall-Petch coeficient from nitrogen content
[25].
6.2 Nanostructured NickelFree Stainless Steels
In recent years, nanostructured materials — also called nano-
materials — has become a subject of research in academic centers
worldwide. Nanostructure can be obtained in many ways. Among
other processes, nickel-free austenitic stainless steel with nano-
structure can be obtained by mechanical alloying. Mechanical
alloying (MA) was developed in the 1970s at the International Nickel
Co. as a technique for dispersing nanosized inclusions into nickel-
based alloys [3]. During the last years, the MA process has been
successfully used to prepare a variety of alloy powders including
powders exhibiting supersaturated solid solutions, quasicrystals,
amorphous phases, and nano-intermetallic compounds. MA
technique has been proven as a novel and promising method for
alloy formation.
