38 Prakt. Met. Sonderband 38 (2006) 
30%, Figure 9. These quantities are remarkably similar to those found in an earlier study due to Bucher 
and Hamburg, where they found approximately 15 and 35%, respectively, were required for these 
strength levels.[20] Of course, the IQ analysis would not appear to be critical in the study of DP steels, 
since the amount of martensite is not only critically important to properties, but also is easily observed 
and measured by typical, quantitative optical microscopy. However, there is no other way to easily 
distinguish among the different kinds of ferrite that exist entering the zinc pot; i.e., cold rolled ferrite 
that has recrystallized in the anneal, cold rolled ferrite that has not recrystallized in the anneal, and new 
ferrite that forms at low temperature during the cooling portion of the process. The first ferrite would 
have a high IQ, while the other two would have a low one. 
04 1 TT 03 
s.. EBSD Data without GB Contribution #DP.580 ++ EBSD Data without GB Contribution BDP-790 
035  ——Polygonal Ferrite ops = Polygonal Ferrite 
03 — Non-Polygonat Ferrite = Non-Polygonal Ferrite 
8 ~——Martensite —— Martensite 
= 025  —+ Sum of all simulated contributions > 92° _, sum of all simulated contributions 
3 02 Eun 
* 0.15 E 2 
0.1 
Ik te 1 ren — or ' . Bien rr He Ap————————— of 
a 10 20 30 40 50 60 70 80 20 100 1c 10 20 30 40 so 60 70 80 90 100 1 
1Q iQ 
rem VaR Pee ERE ww Tree 
80.9 = 838 Polygonal F 80.7 55.4 Polygonal F 
64.3 148 Non-Polygonal F 57.8 14.7 Non-Polygonal F 
387 18.6 Martensite 34... 29.6 Martensite 
Figures 8 and 9: 1Q analysis of the dual-phase microstructure after CGL processing. 
Microstructure of a TRIP Advanced High Strength Steel After CGL Processing 
An investigation has recently been completed in which a low carbon, low Si, high Al, Nb-bearing TRIP 
steel was processed using an intercritical anneal followed by a CGL processing simulation.[19] The 
steels investigated contained 0.15wt%C-1.5%Mn-0.3%Mo-0.03%Nb and Al varying from 0.05 to 1.0%. 
After hot rolling, coiling at 550°C and cold rolling, the steels were heated to the soak temperature, held 
for one minute at temperatures ranging from 750 to 860°C, then cooled at different rates to 450°C, held 
for various times then cooled to RT, again at different rates. The microstructures were observed with 
OM, SEM, TEM and the new EBSD-IQ technique. The retained austenite values were checked by 
magnetometry. The conditions examined were: (i) as-intercritically annealed and WQRT; (ii) annealed 
and cooled to 450°C and WQRT; and (iii) annealed and cooled to 460°C, held for various times at 
450°C and cooled to RT. The i 
. . . . . at 1 5 
An example of the application of the EBSD-IQ technique incorporating the Multi-peak Model is shown 1.0Al 
in Figure 10, which compares the makeup of the microstructure in the 0.05Al and 1.0Al steels after a interc 
one minute anneal and cooling at 15°C/sec to 450°C, followed immediately by water quenching to RT. upon 
The influence of the Al content on the A3 line and kinetics of annealing are striking. The Al appears to woulc 
shift the A3 line to the right and upward, leading to less austenite but probably austenite of a higher the m 
carbon content. The high Al content also seems to accelerate the annealing kinetics. with much more retain. 
recrystallized ferrite in the higher Al steel. of the