Measurement of Particles in Molten Al–Si Alloys Applying the Ultrasonic Technique

Abstract

The present study was undertaken to investigate the capacity of the ultrasonic technique for measuring various particles in liquid aluminum and commercial 356 alloy at two different temperatures each. Particles of TiB2, AlSr, Al3Ti, and Al2O3 were studied using a Metalvision MV20/20 ultrasonic machine. The data provided plots of (1) the cleanliness value, (2) average particle size, and (3) particle count for each particle size range, as a function of testing time. An examination of the microstructure of solidified samples obtained from samplings of the melt was also carried out using Jeol JXA-8900L electron probe microanalyzer. Other techniques, including the liquid metal cleanliness analyzer and all the filtration techniques, can only detect TiB2 particulates when the concentration is very low (less than 10 ppm B). By applying the ultrasonic technique, measurements may be conducted properly for concentrations as high as 90 ppm B; thus, the ultrasonic technique provides an improved alternative for the measurement of TiB2 particulates in liquid aluminum. This fact is of significance, since particles are invariably present because the addition of TiB2 is essential to the grain-refining processes used for aluminum alloys.