Primary dendrite arm spacing effects upon mechanical properties of an Al–3wt%Cu–1wt%Li alloy

Abstract

The imposition of a wide range of operational conditions in foundry and castings processes generates, as a direct consequence, a diversity of solidification structures. It is well known that mechanical properties depend on solidification structures. The literature presents relationships between yield strength and grain size, such as the Hall-Petch’s equation, or ultimate tensile strength and dendrite arm spacing. In this work, an Al–3wt%Cu–1wt%Li alloy was solidified under upward unsteady state heat flow conditions. Heat was directionally extracted only through a water-cooled bottom made of steel (SAE 1020). The aim of the present study is to obtain correlations between the as-cast microstructure, solidification thermal variables and mechanical properties of an Al–3wt%Cu–1wt%Li alloy casting. The results include tip growth rate (VL), cooling rate (Ṫ), primary dendrite arm spacing (λ1), ultimate tensile strength (σUTS) and yield strength (σy) as a function of solidification conditions imposed by the metal/mold system. It is found that the primary dendrite arm spacing decreases with the increase in tip growth rate and cooling rate. In both cases (σUTS and σy = 0.2 %ε), the finer dendritic arrangement presents superior mechanical properties.