Enhanced thermal stability in additive friction stir deposited ODS IN9052 Al alloy

Mechanically alloyed (MA) oxide dispersion strengthened (ODS) IN9052 Al alloy exhibits excellent strength both at ambient and high temperatures (up to 300 °C). The limited ductility at ambient temperatures, stemming primarily from the inherent microstructure, impede its practical appeal in structural applications. The present study signifies a maiden effort to additively manufacture MA-ODS IN9052 alloy using solid-state additive friction stir deposition (AFSD) process which has added advantages of uniform particle dispersion, severe particle breakdown, and a recrystallized microstructure. This study indicates a remarkable transition from the initial strain softening behavior in the as received alloy to significant work hardening in the AFSD condition, while maintaining satisfactory yield strength of ∼380 MPa at ambient temperature highlighting a favorable strength-ductility synergy. Importantly, exceptional thermal stability has been achieved in the AFSD alloy by systematically optimizing the process parameters to engineer microstructural heterogeneity. The AFSD alloy demonstrated an impressive high temperature strength, with ∼22 % and ∼49 % increase in yield strength as compared to forged alloy at 240 °C and 340 °C, respectively. Enhancing high temperature strength in aluminum alloys has been a long standing goal and the current results outperform other commercially available high temperature Al alloys. Excellent thermal stability in the AFSD processed alloy is attributed to the nano-scale carbon-rich cluster formation around oxides and carbides in the matrix. These particles restrict grain boundary sliding and are more effective in dislocation-particle interaction. The findings are supported by detailed TEM and atom probe tomography analysis.