Direct aging of additively manufactured A20X aluminum alloy

This study investigates the effect of direct aging on a newly developed high-performance aluminum alloy A20X for laser powder bed fusion. Three different temperatures (180 degrees C, 200 degrees C, and 220 degrees C) and nine different heat treatment durations (5 min to 30 h) were considered. The material exhibited significant softening (up to 23.7 % hardness drop) after direct aging. The extent of softening was proportional to the temperature and duration of heat treatment. During direct aging, incoherent Al2Cu (theta) precipitates ({110}(theta) vertical bar vertical bar {220}(Al)) coarsened and the volume fraction remained constant (4.52-4.63 %). The average precipitate size grew by up to similar to 100 % through direct aging and no metastable precipitates (such as 0' or Omega) formed, suggesting the absence of supersaturated matrix in as-printed A20X. Accordingly, the yield and tensile strengths of the alloy dropped by up to 27 % and 19.4 %, respectively. The continuous Mg/Ag solute wall observed at grain boundaries in the as-printed state caused serrated plastic flow due to the locking/unlocking of dislocations. Longer aging treatments generated discrete solute co-clusters along the grain boundaries and TiB2/Al interface promoting smoother plastic flow.

Automated summary

This study investigates the effect of direct aging on a newly developed high-performance aluminum alloy A20X for laser powder bed fusion. It is found that direct aging can cause softening of the material, and the extent of softening is proportional to the temperature and duration of heat treatment. During direct aging, the precipitate size grows and no metastable precipitates are formed. Moreover, the presence of solute walls in the as-printed state leads to unstable plastic flow, while longer aging treatments promote smoother plastic flow.