Biomedical Engineering Reference
In-Depth Information
The effect of MA processing was studied by X-ray diffraction
and microstructural investigations. Ni-free austenitic stainless
steels with nanostructure were synthesized by mechanical alloying
(MA), heat treatment, and nitriding of elemental microcrystalline
Fe, Cr, Mn and Mo powders. After 48 h of MA, the alloy
had decomposed into an amorphous phase and nanocrystalline
α-Fe [29]. Heat treatment performed after MA process results in
crystallization into ferritic phase. Then, compacted material was
nitrided at 1210 o C, which resulted in phase transformation from
ferritic to fully austenitic (Fig. 6.6). Average crystallite size of so
produced material increased during processing from 16 to 27 nm.
Figure 6.6 Phase transformation from ferritic (a) to austenitic (b) in
Fe 74 Cr 24 Mo 2 N stainless steel [29].
Using confocal laser scanning microscope, it is possible to
reveal the surface of nanocrystalline nickel-free austenitic stainless
steels. The surface of Fe 54 Cr 24 Mn 21 Mo 1 N sample shown in Fig. 6.7
reveals pores. These pores have irregular shapes and dimensions.
Figure 6.7 Surface of Fe 54 Cr 24 Mn 21 Mo 1 N sample under confocal laser
scanning microscope [30].
 
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