Effect of Cooling Rate on W-Phase Formation in Al-Cu-Sc Alloys

Aluminum-copper-scandium alloys show significant potential for high-strength applications; however, the formation of the detrimental W-phase (nominally Al8Cu4Sc) has prevented commercial adoption. There is not a strong consensus as to what conditions lead to the formation of W-phase, but two key factors are the cooling rate during solidification and the homogenization heat treatment. In this work, the effect of cooling rate on the formation of W-phase in Al-Cu-Sc alloys is investigated utilizing wedge molds that produce solidification rates from ~0.25 to 100 K/s. Samples are examined in both the as-cast state and following homogenization and aging treatments.