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<p>This study systematically investigates the effects of solution treatment (S. S.) temperature (450-500&#xa0;°C) on the microstructure, mechanical properties, and Portevin-Le Chatelier (PLC) effect of Al-5Mg-2.5Li alloy. At lower S. S. temperatures (450-470&#xa0;°C), the alloy retained a fine grain size (~9&#xa0;µm) with minimal Li oxidation, whereas higher temperatures (480-500&#xa0;°C) induced grain coarsening (&gt;50&#xa0;µm) and severe Li oxidation, forming 10&#xa0;µm-wide Li<sub>2</sub>O bands. Precipitation strengthening dominated the mechanical performance: aging at 450&#xa0;°C after S. S. produced dense δ′-Al<sub>3</sub>Li precipitates. Its hardness can reach 142 HV, and its tensile strength is 502&#xa0;MPa. High-temperature S. S. (500&#xa0;°C) suppressed δ′-Al<sub>3</sub>Li formation due to Li oxidation. The PLC effect exhibited temperature-dependent behavior: aged alloys at 450-470&#xa0;°C showed higher stress drops (Δ<i>σ</i>: ~ 3.9&#xa0;MPa in aging) and B/C-type serrations, attributed to δ′-Al<sub>3</sub>Li shearing and solute-dislocation interactions. At 480-500&#xa0;°C, reduced Li content shifted PLC to Mg-dominated C-type serrations with lower stress drops (Δ<i>σ</i>: ~ 2.3&#xa0;MPa in aging) and higher critical strain (<i>ε</i><sub>C</sub>: ~ 5.3% versus ~ 3.5% at 450-470&#xa0;°C). These findings underscore the critical role of S. S. temperature in balancing Li oxidation, precipitation kinetics, and PLC behavior, guiding the design of high-performance Al-Mg-Li alloys.</p>

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Effect of Solid Solution Temperature on the Microstructure and Mechanical Properties of Al-5Mg-2.5Li Alloy

  • 期刊论文

  • 发表日期：

    2025年7月21日

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  • Fufangzhuo Chai,
  • Ji-ang Du,
  • Yunze Jiang,
  • Chengchao Du

摘要

This study systematically investigates the effects of solution treatment (S. S.) temperature (450-500 °C) on the microstructure, mechanical properties, and Portevin-Le Chatelier (PLC) effect of Al-5Mg-2.5Li alloy. At lower S. S. temperatures (450-470 °C), the alloy retained a fine grain size (~9 µm) with minimal Li oxidation, whereas higher temperatures (480-500 °C) induced grain coarsening (>50 µm) and severe Li oxidation, forming 10 µm-wide Li2O bands. Precipitation strengthening dominated the mechanical performance: aging at 450 °C after S. S. produced dense δ′-Al3Li precipitates. Its hardness can reach 142 HV, and its tensile strength is 502 MPa. High-temperature S. S. (500 °C) suppressed δ′-Al3Li formation due to Li oxidation. The PLC effect exhibited temperature-dependent behavior: aged alloys at 450-470 °C showed higher stress drops (Δσ: ~ 3.9 MPa in aging) and B/C-type serrations, attributed to δ′-Al3Li shearing and solute-dislocation interactions. At 480-500 °C, reduced Li content shifted PLC to Mg-dominated C-type serrations with lower stress drops (Δσ: ~ 2.3 MPa in aging) and higher critical strain (εC: ~ 5.3% versus ~ 3.5% at 450-470 °C). These findings underscore the critical role of S. S. temperature in balancing Li oxidation, precipitation kinetics, and PLC behavior, guiding the design of high-performance Al-Mg-Li alloys.