Precipitation Behavior during Aging Operations in an Ultrafine-Grained Al–Cu–Mg Alloy Produced by High-Strain-Rate Processing

Abstract

An ultrafine-grained (UFG) Al–Cu–Mg alloy (AA2024) was produced by surface mechanical grinding treatment (SMGT) with a high strain rate, and the precipitation behavior inside the grain and at the grain boundary was investigated. During SMGT, element segregation at the boundary was rarely observed, since the solute atoms were impeded by dislocations produced during SMGT. During early aging, the atomic fraction of Cu at the grain boundary with SMGT alloys was approximately 2.4-fold larger than that without SMGT alloys, the diffusion rate of Cu atoms from the grain toward the grain boundaries was accelerated with SMGT alloys, because a higher local elastic stress and diffusion path were provided by high-density dislocations. The combined action, in terms of the composition of the alloy, the atomic radius, the diffusion path, and the diffusion driving force provided by high-density dislocations with SMGT alloys, led to a Cu/Mg atomic ratio of approximately 6.8 at the grain boundary. The average size of the precipitates inside the grain was approximately 2- and 10-fold larger than that formed after later aging with and without SMGT alloys, due to more nucleation sites at dislocation located inside the grain with SMGT alloys having attracted and captured numerous solute atoms during the aging process.

Effect of Copper Segregation at Low-Angle Grain Boundaries on the Mechanisms of Plastic Relaxation in Nanocrystalline Aluminum: An Atomistic Study

“…Note that a large density of these LAGBs may hinder plastic deformation and improve the strength of these materials [2][3][4]. Thus, knowledge of unambiguous relationships between the microstructure and macroscopic mechanical behavior, as well as their features related with alloying, is important to design new approaches for strengthening [1][2][3][4][5][6][7][8]. However, the microstructural analysis of empirical results related with a phenomenon does not provide a deep insight into these fundamental processes to adjust mechanical properties more accurately.…”

“…In aluminum alloys, Cu is known to be an important alloying element demonstrating a prominent strengthening effect by the forming of intermetallic particles [3][4][5][6][7][8]. However, this element also tends to segregate at lattice dislocations and grain boundaries [3][4][5]7].…”

“…In aluminum alloys, Cu is known to be an important alloying element demonstrating a prominent strengthening effect by the forming of intermetallic particles [3][4][5][6][7][8]. However, this element also tends to segregate at lattice dislocations and grain boundaries [3][4][5]7]. The effect of the alloying atom segregation on the properties of GBs and their contribution to the mechanical properties of aluminum alloys have been intensely studied in [4,7,[14][15][16][17].…”

“…However, this element also tends to segregate at lattice dislocations and grain boundaries [3][4][5]7]. The effect of the alloying atom segregation on the properties of GBs and their contribution to the mechanical properties of aluminum alloys have been intensely studied in [4,7,[14][15][16][17]. This effect is studied with MD in [14,15] considering the effect of Mg segregation.…”

“…This effect is studied with MD in [14,15] considering the effect of Mg segregation. The contribution to the mechanical properties of aluminum alloys have been intensely studied in [4,7,[14][15][16][17]. This effect is studied with MD in [14,15] considering the effect of Mg segregation.…”