Technology for Modifying Aluminum Alloys with Ultrafine Silicon

Resumo

Results are provided for a study of the structure and mechanical properties of alloy AK12 modified with tabletted ultra-finely dispersed modifier based on silicon carbide, introduced “beneath a metal stream” without additional mixing, and in a rotary device. It is established that the optimum method for introducing modifier is that of “beneath a metal stream.” In this case the ultimate breaking strength increases from 110 to 150 MPa, nominal yield strength from 85 to 94 MPa, and relative elongation from 2.3 to 6.2% (metal pouring temperature into a mold 750 °C). Metallographic examination is used to determine the reduction in macro-grain size in test pigs (ingots) by a factor of four compared with control alloys, absence of porosity, and an increase in ingot density from 2.59 to 2.66 g/cm³. Introduction of ultra-finely dispersed modifier based on silicon carbide increases the number of crystallization centers in a 1 kg ingot to 2·10¹¹ units.