Achieving isotropic mechanical properties in Al–Cu–Li alloys is critical for next-generation aerospace structures, yet remains challenging due to complex interactions between deformation textures and precipitate distributions. This study systematically investigates the effect of strain path variations—unidirectional (CP-I) versus non-unidirectional (CP-II)—on microstructure, texture evolution, and mechanical anisotropy of AA 2199 sheets processed via cold rolling, solution treatment, and aging (ST-AA). True von Mises strains corresponding to 60%, 75%, and 90% reductions (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12666_2025_3648_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="11" /> </InlineMediaObject> <EquationSource Format="TEX">$\bar{\varepsilon}$</EquationSource> <EquationSource Format="MATHML"><math> <mover accent="true"> <mrow> <mi>ε</mi> </mrow> <mrow> <mo stretchy="false">¯</mo> </mrow> </mover> </math></EquationSource> </InlineEquation> = 0.75, 1.17, 1.88) were employed to quantify deformation effects. The CP-IISTAA route at 75% deformation (<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12666_2025_3648_Article_IEq2.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="83" /> </InlineMediaObject> <EquationSource Format="TEX">$varepsilon$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="italic">varepsilon</mi> </mrow> </math></EquationSource> </InlineEquation> = 1.17) produced fine, equiaxed grains (13–20 μm), dominant ND rotated cube texture (volume fraction ≈ 18%), and a uniform distribution of T1 and θ′ precipitates. This synergistic microstructure minimized yield strength anisotropy (YS45/YS0 ≈ 0.98) while achieving high yield strength (~440 MPa) and ultimate tensile strength (~500 MPa). These results establish a robust processing pathway for fabricating Al-Cu-Li sheets with superior isotropic mechanical properties for aerospace applications.

Effect of Downstream Processing on Mechanical Properties, Microstructures, and Evolution of Texture in Aluminum–Copper–Lithium (AA 2199) Alloy

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发表日期：

2025年7月22日

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A. P. Murugesan,
Ashok Kumar,
Manoj Humane

摘要

Achieving isotropic mechanical properties in Al–Cu–Li alloys is critical for next-generation aerospace structures, yet remains challenging due to complex interactions between deformation textures and precipitate distributions. This study systematically investigates the effect of strain path variations—unidirectional (CP-I) versus non-unidirectional (CP-II)—on microstructure, texture evolution, and mechanical anisotropy of AA 2199 sheets processed via cold rolling, solution treatment, and aging (ST-AA). True von Mises strains corresponding to 60%, 75%, and 90% reductions ( $\bar{\varepsilon}$ $\bar{ε}$ = 0.75, 1.17, 1.88) were employed to quantify deformation effects. The CP-IISTAA route at 75% deformation ( $varepsilon$ $varepsilon$ = 1.17) produced fine, equiaxed grains (13–20 μm), dominant ND rotated cube texture (volume fraction ≈ 18%), and a uniform distribution of T₁ and θ′ precipitates. This synergistic microstructure minimized yield strength anisotropy (YS₄₅/YS₀ ≈ 0.98) while achieving high yield strength (~440 MPa) and ultimate tensile strength (~500 MPa). These results establish a robust processing pathway for fabricating Al-Cu-Li sheets with superior isotropic mechanical properties for aerospace applications.