Quantitative approach to realization of ultrasonic grain refinement of Al-7Si-2Cu-1Mg alloy

Abstract

Ultrasonic melt treatment (UST) was applied to Al-7Si-2Cu-1Mg melt at various temperatures of 620, 650, 700 and 785 °C. MgAl2O4 particles which were often found to be densely populated along oxide films, became effectively dispersed and well-wetted by UST. Transmission electron microscopy work combined with crystallography analysis clearly indicates that MgAl2O4 particles can act as α-Al nucleation site with the aid of UST. However, with UST, grain refinement occurred only at temperature of 620 °C and the grain size increased from 97 to 351 μm with increase of melt temperature to 785 °C for UST. In quantitative analysis of grain size and MgAl2O4 particle diameter, it was found that ultrasonic de-agglomeration decreased mean particle size of the MgAl2O4 particles, significantly reducing size from 1.2 to 0.4 μm when temperature increased from 620 to 785 °C. Such a size reduction with increased number of MgAl2O4 particles does not always guarantee grain refinement. Thus, in this work, detailed condition for achieving grain refinement by UST is discussed based on quantitative measurement. Furthermore, we tried to suggest the most valid grain refinement mechanism among the known mechanisms by investigation of the relationship between grain size and particle size with variation of melt temperature.

Grain refinement of commercially pure aluminum with addition of Ti and Zr elements based on crystallography orientation

“…The physical method refines the grain by introducing physical factors into the solidification process. After using ultrasonic treatment in the solidification process, the grain size of commercial pure aluminum and Al-Si-Cu alloy is greatly refined compared to the alloy without ultrasonic treatment 17,18 . By applying electric and magnetic fields of different strengths during the solidification process, the grains of the Al-Si alloy are also greatly refined 19 .…”

Ceramic Sonotrodes for Light Alloy Melt Treatment

“…[13][14][15] Melt treatment by ultrasonic excitation, in particular, had significant advances in the last decade. This physical processing is known to promote grain/intermetallic refinement, [16][17][18][19] melt degassing 20,21 and reinforcement particle dispersion, [22][23][24][25][26][27][28] having been successfully applied to different alloys. [29][30][31][32] This technique, however, has problems due to its application in high-temperatures and the use of metallic sonotrodes that may have an affinity to react with the melts.…”