Prakt. Met. Sonderband 46 (2014) 127
ı situ [5-11]. 3. RESULTS
bserved up
justment of 3.1 SETTING A DEFINED INITIAL MICROSTRUCTURE BY AUSTENITIZATION
interactions
lusions and The austenite grain size is one of the major influencing parameters for the formation of AF.
es on the Therefore the setting of a defined austenite grain size before cooling the sample, in which
sonventional the formation of AF occurs, and the determination of the austenite grain size are essential
es are heat for a systematic investigation of the AF nucleation.
n of the final A standardized method for the determination of the austenite grain size [16] exists, but
5 paid to the within this study a computerized method is used in order to achieve optimized results with
eters on the less time effort. Due to the small observed area in the HT-LSCM the analysis of austenite
efits of the grain size is done best by optical microscopy after HT-LSCM treatment. For the grain size
ited out. determination on the sample surface no chemical etching is necessary because of the
thermal etching during the HT-LSCM treatment. The determination of austenite grain size
inside the sample can be done after etching with picric acid. Fig. 2 illustrates the procedure
of austenite grain size analysis, which is a combination of manual and computer based
evaluation. Based on this computer aided method grain size distribution can be
in Ti-alloyed determined, in contrast to the standardized methods [16] which just provide the amount of
re done with grains per length or area unit.
um induction
the melt on
was already
e HT-LSCM.
ind austenite
w about the
n the project Grain Size Tum
Thermal etched Retraced austenite Computer based Grain size
m sample surface => grain boundaries => evaluation => distributation
fetallo- Fig. 2: Procedure of austenite grain size analysis
yraphy /
= In Fig. 3 the influence of austenitizing temperature on the austenite grain size is illustrated.
It can be seen that the mean grain size increases with increasing treatment temperature.
#0 po 00ST =1400°C
JST T= 1300 °C Ty = 1200 °C
Tan > 1200°C
Analysis of 5 1000
LSCM samples 2
pe 5
sy : a.
Microscopy vs /250 “Cimin + = 4400°C
f a
/ 7
200 400 600 5 200 400 600
time {s] Austenite Grain Size [pm]
Fig. 3: Tested austenitizing temperatures and the corresponding austenite grain size
an distributions
tion