**Abstract**

One of the prime challenges with age hardened Al-Cu alloys is the strength degradation at high temperatures (above �250°C) due to the coarsening of strengthening θ<sup>0</sup> precipitates and associated metastable θ<sup>0</sup> ! stable θ phase transformation. A recent discovery suggests that micro-alloying with Manganese (Mn) and Zirconium (Zr) can synergistically restrict θ<sup>0</sup> precipitate coarsening, thereby rendering an excellent high temperature stability for Al-Cu-Mn-Zr (ACMZ) alloys. The θ<sup>0</sup> precipitates are stabilized primarily from the reduction of interfacial energy by preferential solute segregation (Mn & Zr) at θ<sup>0</sup> precipitate/α-Al matrix interfaces. The Al-Cu-Mn-Zr alloys thereby exhibit excellent high temperature hardness and tensile properties (yield and ultimate tensile strength) in addition to superior fatigue life and creep resistance. This newly developed Al-Cu-Mn-Zr alloys also showed excellent hot tearing resistance compared to the conventional cast Al-Cu alloys so much so that it meets the industrial standards as well. These alloys also have promising manufacturing possibility by additive route. Overall, Al-Cu-Mn-Zr alloys offer great potential for the automotive industry because of their unprecedented high temperature performance which should enable engineers to build light weight passenger vehicles leading to a safer and greener environment.

**Keywords:** Al-Cu-Mn-Zr alloy, precipitate strengthening, high temperature stability, solute segregation, mechanical property, additive manufacturing
