92 Prakt. Met. Sonderband 46 (2014) 
abnormal grain growth, see Fig. 3b, and 3c. It is important to note that this “abnormal” 
grain growth is completely differs from that already described in grain-oriented steels [5]. 
The mentioned grain growth is induced by deformation or in other words by dislocations 
created in grains after applied deformation. 
_ i ar 
Fig. 4 Sample F1A of the investigated steel with stepwise deformation gradient after 
annealing at 900°C for 300 sec: a) area with stepwise deformation changes from € -0% 
to £~4%, b) area with stepwise deformation changes from £~4% to £ ~6% deformation 
Completely different deformation gradients mode is presented in Figs.4a and 4b. The 
deformation gradients mode was realized here in stepwise form. It means that the sample 
was deformed by the form illustrated on the Fig.1b. This leads to generation of deformation 
in stepwise character. The Fig.4a represents the first stepwise deformation. The sadden 
change in sample thickness is visible in this figure. The deformation in this area changes 
from 0% to 4% in stepwise character. The mentioned deformation changes are reflected 
by microstructure change in this area, see Fig. 4a. As one can see the microstructure of b 
the region with deformation of 0% is completely differs from that at the region with 4% ) ; 
deformation. Here, it is clearly visible that the grains in deformed area have much larger Fig. 6 Loc 
size than ones in the region without deformation. As one can see the mean grain size in map obtair 
the area without deformation is about 30-40um. However, the mean grain size of the wg o 
deformed region is about 300um, see the left and the right side of Fig. 4a, respectively. or ; 
| ; . i eformation 
Fig.4b represents area of investigated steel sheet with deformation of 6%. As one can see misorientati 
this deformation has led to huge grains creation in this region. The average size of the the microstr 
grains in this region is about 400um. Moreover, the microstructure in Fig.4b does not 
contain the grains with mean size about 30-40um as it was observed in previous case, 
compare Fig. 4a (left side) with Fig. 4b. Hence, as one can conclude, there is a particular 
deformation which leads to the optimal microstructure of investigated steel, from grain size 
and grain area distribution point of view. 
The microstructure obtained after laboratory treatment of the investigated material with 
gradient deformation involved by hardness test machine is presented in Fig. 5. As one can 
see, impress is localized in small field near the sample surface. Generated in this way 
strain allowed to follow grain growth progress in surface area where the impress was 
applied after applied annealing process. The dependence of grain boundary motion on 
generated deformation stress one can follow in the Fig. 5a, 5b and 5c. Fig. 7 PI 
As one can see, there are different types of microstructure developed after application of Investigated 
different impress deformation and subsequent annealing at 900°C for 2 min., see Fig. 5. It after applic 
is interesting to note that, these series of experimental samples have a precise line of deformation 
distinction among themselves. As one can see, the fraction of small grains (grain size ~ 25 heat treatm: 
um ) is about ~70% of the total area of sample. It is an area where the process of second min. 
recrvstallization has been not started. The arain size of the huae arains is about 200 — 500 
accumulated 
intensity of ti 
These confirr 
of the steel sl 
I The IPF me 
Fig. 5 Sample of the investigated F1A steel with: a) £~2,2%, b) £~3,8%, ¢) £~6,8% deformation 
impress deformation, annealed at 900°C for 2 min in pure hydrogen atmosphere.