New Infiltration Patterns During Pressureless Infiltration of Partially Nitrided Aluminium Preforms

摘要

Green samples of AA 6061-2Mg-1Sn-3Nylon were processed at 560°C for 12hr under nitrogen to form a contiguous and rigid AIN skeleton. These partially nitrided preforms were then infiltrated with Al-Si alloys of different compositions at various temperatures. When the preforms were infiltrated with a near eutectic Al-Si alloy at a small melt superheat, infiltration occurred in a conventional slug-flow fashion where infiltration proceeded through the advance of a single well-defined infiltration front, which separates the infiltrated and un-infiltrated regions. However, as the infiltration conditions deviate from the eutectic point, either by changing the alloy composition or increasing the melt superheat, the infiltration pattern changes progressively from slug flow to extreme non-slug flow, where infiltration proceeded uniformly across the entire preform without showing a clear infiltration front. The existence of different infiltration patterns is attributed to the competition between thermodynamic and kinetic factors.