Competing nucleation of single- and double-layer Guinier–Preston zones in Al–Cu alloys

Abstract

Solid-state precipitation is a key heat-treatment strategy for strengthening engineering alloys. Therefore, predicting the precipitation process of localized solute-rich clusters, such as Guinier–Preston (GP) zones, is necessary. We quantitatively evaluated the critical nucleus size and nucleation barrier of GP zones in Al–Cu alloys, illustrating the precipitation preferences of single-layer (GP1) and double-layer (GP2) GP zones. Based on classical nucleation theory using an effective multi-body potential for dilute Al–Cu systems, our model predicted GP1 and GP2 precipitation sequences at various temperatures and Cu concentrations in a manner consistent with experimental observations. The crossover between formation enthalpy curves of GP1 and GP2 with increasing cluster size determines the critical conditions under which GP2 zones can nucleate without prior formation of GP1 zones. This relationship reflects competing interactions within and between clusters. The results illustrate the underlying mechanisms of competing nucleation between zones, and provide guidance for tailoring aging conditions to achieve desired mechanical properties for specific applications.

Influence of Structure Development on Performance of Copper Composites Processed via Intensive Plastic Deformation

“…Additions of alloying elements usually result in the formation of strengthening precipitates, but deteriorations in electroconductivity. For example, combining Cu with Al typically results in strengthening via formation of the GP (Guinier Preston) zones [ 60 , 61 ]. Adding small amounts of elements known for their strengthening ability can be favored, too; adding Ti imparts the formation of the α-Cu 4 Ti phase [ 62 ].…”