in as-forged condition and after 50 hours homogenization. rll: 
The technique used for assessing the microsegregation degree,although „ith 
semi-quantitative, was satisfactory since the differences in diagrams, analyZ 
segregation ratios and coefficient of variation are well defined. i 
Assuming that concentration profile varies sinusoidally along a LL 
distance x, the equation of this profile with regard to distance and Co 
time is given as follows (15), Co 
C=concentration ee 
, C=-average concentration +he 35 
C(x,t)=T+8sin (1X) exp (=D ) (1) D=diffusion coefficient 
1 l=segregation distance 
B=constant The av 
With the boundary conditions which give the maximum and minimum Toe 
concentration at «=1/2 and x=>1/2 respectively, in t=0 and t=t, the Te 
following expression can be obtained : 
t t : N 
Cy - Co I. (ty (2) Cy=maximum concentration 
Ch - Ca a P 17 C,=minimum concentration 
The first member of equation (2) is called index of residual These 
segregation 8, normally used for the study of homogenization hee 
kinetics (16) Obtaining these values §, it is possible to calculate COrTES! 
the diffusion coefficient D. 119720 
The X-ray intensities obtained in this paper are related with the 
concentraticn of the elements. Thus, the maximum and minimum 
intensity values qualitatively represent the maximum and minimum 4. CON 
concentration. It is possible to determine § by replacing the Cy 
and Co by the maximum and minimum intensity values, through the HL 
following expression : Fe - 1t To 1» Where the term To/Tb is - 
“le Te . — 1NQ1C8 
—t 
Ig - In, T 
used to normalize the expression with relation to the average co 
intensities obtained for each time. Ta 
For each element, taking the average of ten greater values of X-ray It is 
intensities as Ty and the average of ten lower values as Ios the En 
obtained values of § with regard to time result in the plot shown in throun 
Figure 16. 
The theoretical model aforementioned takes into account a sinusoidal a 
Prakt. Met. Sonderbd. 21 (1990) 
148