Investment casting is one of the best modern technology in the world, it is involved in many components of industries, the manufacturing of spare parts of cars, aircraft and turbine blades are the most important industries which using investment casting for production. This study focused on the aluminum alloy (356A) which has good mechanical properties in addition to the liquidity characteristic that helps fill all parts of the mold during the casting process. The experiments and tests conducted on these castings show that heat treatment processes improve the mechanical properties, especially tensile tests and hardness, where tensile strength and hardness have doubled, while as there is no obvious change in elongation