Microstructural Evolution in a 17-4 PH Stainless Steel after Aging at ...

Fe & Cr / at. %
(a)
(b)
Ni
Si
Cu
Cr
Cu
100
80
60
40
20
0
30
15
0
30
15
0
70
50
30
10
0
~30nm
0 5 10 15 20 25
Depth / ~nm
~9nm
Fig. 7 3DAP elemental mapping of the martensite phase aged at
580°C for 4 h. (a) The phase decomposition into Cr enriched and
depleted region occur in the martensite phase. (b) Fine spherical
Cu rich precipitate. (c) Concentration depth profile obtained from
the selected region near the Cu precipitate.
is a typical feature of spinodal decomposition. The periodicity
of the fluctuation is on the order of 3 nm. The
Cu mapping shows that Cu-enriched particles approximately
8 nm in diameter are present. In direct contact
with one of the Cu particle, a Ni and Si enriched particle
is observed as indicated by an arrow in Figure
10(b). Such fine particles are always observed in contact
with Cu precipitates, and they are believed to be
the G-phase based on the TEM observation shown in
Figure 8. Figure 10 (c) shows concentration depth profiles
across the Cu precipitate and the G-phase indi-
Fe
Cr
Published in Metall. Mater. Trans. A. Vol. 30A, pp. 345-353. 1999
Fe &Cr / at.%
(a)
(b)
110
110
(c) 011
200
(d)
100nm
Fig. 8 TEM (a) dark filed image, (b) [001], (c) [011] and (d) [111]
SAD pattern of the martensite phase aged 400°C for 5000 h. The
dark field image was taken using the 1/2(011) reflection.
Ni
Si
Mn
Cu
100
80
60
40
20
0
30
15
0
30
15
0
10
0
30
15
0
0 500 1000 1500
Number of Atoms / x50
Fig. 9 1DAP concentration depth profile of the martensite phase
aged at 400°C for 5000 h. Ni, Si, and Mn appear to be partitioned
into the Cu precipitate.
110
011