Key Takeaways & Executive Findings
- •• Tensile creep deformation exceeds compressive creep in 2219 aluminum alloy at 165°C, with compressive creep rate increasing more significantly at higher stress levels. • Compressive stress creep-ageing yields higher strength than stress-free ageing, while tensile ageing results in the lowest strength, highlighting the influence of stress state on mechanical properties. • Precipitate orientation is stress-dependent: tensile stress aligns precipitates parallel to stress, compressive stress perpendicular, with orientation becoming more pronounced over time. • A unified physics-based constitutive model accurately predicts creep-ageing behavior under both tension and compression, enabling precise forming of complex components.
Abstract
The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165 ℃ for different time. The results indicated that the creep deformation under tensile stress was greater than that under compressive stress. As the stress level increases, the compressive creep rate showed more significant increase. The yield strength after compressive stress creep-ageing was higher than that after stress-free ageing, with the lowest strength observed in the tensile-aged sample. Overall, the average phase length after compressive stress creep-ageing was larger than after tensile stress ageing. Under tensile stress, the number and size of precipitates at small angles to the stress direction were larger than those perpendicular to the stress direction. In contrast, under compressive stress, this relationship was reversed, and the preferential orientation of phases became more pronounced with ageing time. A unified, physics-based creep-ageing constitutive model, accounting for the orientation of precipitation, was developed for both tensile and compressive stress conditions. The predicted results were in good agreement with the experimental data. These findings, along with the developed model, provide a theoretical and simulation basis for precise creep-ageing forming of components under complex stresses.
1. Introduction
Aluminum alloy is widely used in key bearing structures of spacecraft due to its lightweight and high strength [1 −3]. The age-strengthened 2219 aluminum alloy has excellent high-and-low temperature performance, exceptional weldability, and high specific strength [4 −8]. By utilizing the creep and ageing strengthening characteristics of aluminum alloy, the creep-ageing forming process can simultaneously enhance both the forming and strength of thin-walled aluminum alloy components within the same thermal environment [9 −11].
During creep-ageing forming, structure parts are bent through mechanical or vacuum loading, making them contact with the mold surface. As a result, the stress distribution transitions from tensile on the outer surface to compressive on the inner surface, particularly in high-rib or large-curvature structures. Therefore, studying the impact of stress state on the creep deformation and microstructure of aluminum alloys at high temperatures during creep-ageing forming process is of significant importance [12, 13].
The asymmetrical nature of deformation and strength under tensile and compressive stress has been studied by several researchers. ZHANG et al [14] found that the tensile/compressive asymmetry of ZL109 aluminum alloy varied with temperature. At high temperature, the difference in creep rate between tensile and compressive stress is significant, while at low temperature, the difference is minimal. XU et al [15] observed that the creep strain of Al-Mg-Cu alloy under compressive stress is smaller than that under tensile stress, with both deformation mechanisms dominated by dislocation slip. They found that compressive stress could promote the formation of S phase in aluminum matrix while inhibited the formation of grain boundary phase, thereby improving the material strength and resulting in low creep strain. YIN et al [16] studied the tension-compression yield asymmetry of extruded Mg-Y sheets and found that tensile yield strength was greater than compressive yield strength due to the activation of different temperature slip systems. Their results further suggest that adding rare-earth element Y can reduce yield asymmetry. TOMCZYK et al [17] found that the fatigue life of 2024-T3511 aluminum alloy could be improved by increasing the initial creep temperature or pre-deformation level during tensile/compressive creep. LENZ et al [18] observed that the creep strain of polycrystalline cobalt-based superalloy under tensile stress was twice that under compression, a difference attributed to the formation of mechanical twins. YAMASHITA et al [19] explained the tension and compression asymmetry of yield strength of Ni-based superalloys using the thermal activated cross-slip model. FISCH
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LI Shuang-bo, MAO Xiao-bo, ZHAN Li-hua, YANG You-liang, LIU Chun-hui, ZENG Quan-qing (2025). Experimental study and creep constitutive modeling for 2219 aluminum alloy under tension and compression conditions. Journal of Central South University. https://doi.org/10.1007/s11771-025-6123-z
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Frequently Asked Questions
What is the main objective of this study?
The study experimentally investigates the creep deformation and mechanical properties of 2219 aluminum alloy under both tensile and compressive stress at 165°C, and develops a unified constitutive model to predict creep-ageing behavior for precise forming of complex components.
How does tensile stress affect creep deformation compared to compressive stress?
Tensile stress results in greater creep deformation than compressive stress. Additionally, as stress level increases, the compressive creep rate increases more significantly.
What is the effect of stress state on yield strength after creep-ageing?
Compressive stress creep-ageing yields higher strength than stress-free ageing, while tensile ageing results in the lowest strength, indicating that compressive stress can enhance strengthening.
How does stress state influence precipitate orientation?
Under tensile stress, precipitates align preferentially at small angles to the stress direction, while under compressive stress, they align perpendicular to the stress direction. This orientation becomes more pronounced with ageing time.
What is the significance of the developed constitutive model?
The model is physics-based and accounts for precipitate orientation, accurately predicting creep-ageing behavior under both tension and compression. It provides a theoretical basis for simulation and precise forming of components under complex stress states.
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