Nanotechnology-Enabled Rapid Investment Casting of AA7075 Smartwatch Enclosures

Abstract

Aluminum alloy 7075 offers exceptional specific strength for consumer and aerospace applications, yet its wide freezing range leads to severe hot cracking and poor fluidity, and a strong tendency for surface defects, making thin-walled components extremely difficult to cast. This study applies nano-treating, where a small fraction of TiC nanoparticles is dispersed into AA7075, to modify solidification behavior and improve castability. The nano-treated alloy exhibited enhanced fluidity, refined grains, delayed solidification, and improved melt–mold wettability, enabling complete filling and the elimination of hot cracking during vacuum-assisted rapid investment casting. Using this enhanced castability, 1 mm thick cosmetic-grade smart watch enclosures were successfully produced from nano-treated AA7075. Previous mechanical results further indicate that the T6 cast result approaches the hardness of wrought AA7075-T6. These findings demonstrate that nanotechnology-enabled casting expands the manufacturable design space of AA7075 and provides a rare defect-free casting solution, offering a pathway to produce high-quality thin-wall components that traditionally rely on full CNC machining.