Influence of Natural Aging on Microstructure and Mechanical Properties of Gravity Casting Al-Cu-Mg Alloy

Abstract For the Al-5.0Cu-0.8Mg alloy fabricated by gravity casting, the 12h natural aging was added between the solution and artificial aging to study its influence on the microstructure and mechanical properties. The transitional phases form during the natural aging following the solution, leading to a significant increase in microhardness. Meanwhile, this microstructure variation accelerates the formation and growth of stable strengthening phases in the same artificial aging. Unfortunately, the 12 h natural aging added in this work excessively coarsens the precipitation, which results in the mechanical properties reduction including ultimate stress from 332 MPa to 302 MPa, especially the elongation from 8.1% to 3.7%. The results indicate that exploring the favorable match of natural and artificial aging is significant to further finely control the precipitation characteristic, which contributes to better mechanical properties of the Al-Cu-Mg alloy.