Second phase measurement Atter (2! 
what 
For determination of amount of the second phase the probes were embedded and the polished = | 
transverse sections were etched at 70°C in 25% HNO; + water solution. Characteristic morphology "4a 
of the eutectic is shown in Fig. 2. 
a., normal eutectic b., degenerated eutectic 
Fig. 2: Typical morphologies of the eutectic, v= 8x10 m/s 
First the amount of AL,Cu phase was measured. This phase can be measured accurately only at high 
magnification (~6400x), because it has small size. Because of the high magnification, the analysis 
should be performed on large number of visual fields (500~1000) to reduce the error in 
measurement. The amount of eutectic, which can be measured with proper accuracy at low 
magnification, also cannot be determined unequivocally if the quantity of the degenerated part of Doers 
eutectic is unknown. Therefore the following method was worked out for the second phase 
measurement. First the ratio of second phase and eutectic was determined at high magnification. For meas. 
The micrographs of the solidified structure were transformed by using the image analyser. The specimens 
eutectic was detected and it edges were drawn around then using the binary identification operation Twix : 
the eutectic fields were filled up. In these pictures, the amount of the eutectic as well as the Al,Cu Fir ¢ 
phase was measured and from these data the ratio of AL,Cu phase was calculated (0.54). The 
measuring method is presented in Fig. 3. 
yi 2am, 
a., Detect and drawing around b., Binary Identification: Fill Holes 
Fig. 3: Measuring method for determination of the ratio of AL,Cu phase, v= 8x10™ m/s 
30)