| Morphology, size distribution, microstructure and hardness of Al-5wt % Pb and Al-10wt %Pb alloy powder were studied, which were processed by centrifugal atomization. To investigate the dispersion characteristics of lead, the temperature of atomization has been varied from 30℃ to 60℃ of the two-liquid phase line. Also, the solidified structure and cooling rate of the powder have been examined. The shape of particles are tear-drop-like, ligament, irregular and the particle size varies from 20 ㎛ to 600 ㎛. For the S. E. M. observation, Back-Scattered Image technique was applied. Within the experimental conditions, it was found that the lead particles were thoroughly dispersed in the matrix. In the case of powders which were smaller than 150 ㎛ (-100+325mesh), Pb particles existed as fine and uniform dispersoids (1㎛ - 3㎛) throughout the Al matrix. However, providing the atomized temperature of melt was 60℃ below the two-liquid phase line, segregation of Pb became significant. The degree of segregation of Al-10wt % Pb was more than that of Al-5wt % Pb. At 30℃ below the two-liquid phase line, the size of dispersed Pb particle became irregular in the powder size above 200 ㎛. The cooling rate of the powder was calculated to be l0²-10⁴K/s. |
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