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<p>This study examines the effect of heat input on the microstructure and mechanical properties of friction stir welded Aluminum-copper joints. To emphasize the role of heat input in determining joint characteristics, two distinct traverse speeds, namely 0.5 mm/s representing a high heat input (HHI), and 2.5 mm/s, corresponding to a low heat input (LHI) were selected, while maintaining a constant tool rotational speed of 800 rpm. Heat input significantly influenced the thermal profiles, material flow, and phase formation. At 0.5 mm/s, the prolonged tool interaction promoted higher heat accumulation, raising the peak temperature on copper side to ~400&#xa0;°C and on the Aluminum side to ~290&#xa0;°C. Conversely, at 2.5 mm/s, rapid tool movement generated steeper thermal gradients, with peak temperatures of ~&#xa0;375&#xa0;°C and 275&#xa0;°C on the copper and aluminum sides, respectively. Macrostructural analysis revealed that the stir zone (SZ) consisted layered copper, a mixed region, and bulk copper particles. At HHI, abundant layered copper and bulk particles were observed in the lower SZ. However, at LHI, larger copper particles accumulated at the SZ bottom due to reduced shearing and insufficient material transfer. The average Cu particle size in the SZ increased from 7&#xa0;µm at HHI to 31 µm at LHI. EBSD analysis indicated that grain refinement was influenced by heat input, with mean grain sizes of 0.99&#xa0;µm at LHI and 1.14 µm at HHI. Hardness in the SZ reached 166 HV<sub>0.1</sub> at HHI, attributed to copper particles dispersion and IMCs formation (Al<sub>2</sub>Cu and Al<sub>4</sub>Cu<sub>9</sub>). Mechanical testing indicated a decrease in UTS from 119.05&#xa0;MPa at HHI to 106.82 MPa at LHI, corresponding to joint efficiencies of 63.32% and 56.82%. Fractography showed brittle failure features at LHI, with cleavage facets and iron-aluminum phases acting as crack initiation sites. Such Al-Cu joints hold considerable importance in electrical applications, such as busbars.</p>

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Effect of Heat Input on the Microstructure Evolution and Mechanical Properties of Friction Stir Welded Aluminum-Copper Joints

  • 期刊论文

  • 发表日期：

    2025年10月31日

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  • Tanmoy Medhi,
  • Smrity Choudhury,
  • Pankaj Biswas,
  • Arunkumar Thirugnanasambandam,
  • Barnik Saha Roy

摘要

This study examines the effect of heat input on the microstructure and mechanical properties of friction stir welded Aluminum-copper joints. To emphasize the role of heat input in determining joint characteristics, two distinct traverse speeds, namely 0.5 mm/s representing a high heat input (HHI), and 2.5 mm/s, corresponding to a low heat input (LHI) were selected, while maintaining a constant tool rotational speed of 800 rpm. Heat input significantly influenced the thermal profiles, material flow, and phase formation. At 0.5 mm/s, the prolonged tool interaction promoted higher heat accumulation, raising the peak temperature on copper side to ~400 °C and on the Aluminum side to ~290 °C. Conversely, at 2.5 mm/s, rapid tool movement generated steeper thermal gradients, with peak temperatures of ~ 375 °C and 275 °C on the copper and aluminum sides, respectively. Macrostructural analysis revealed that the stir zone (SZ) consisted layered copper, a mixed region, and bulk copper particles. At HHI, abundant layered copper and bulk particles were observed in the lower SZ. However, at LHI, larger copper particles accumulated at the SZ bottom due to reduced shearing and insufficient material transfer. The average Cu particle size in the SZ increased from 7 µm at HHI to 31 µm at LHI. EBSD analysis indicated that grain refinement was influenced by heat input, with mean grain sizes of 0.99 µm at LHI and 1.14 µm at HHI. Hardness in the SZ reached 166 HV0.1 at HHI, attributed to copper particles dispersion and IMCs formation (Al2Cu and Al4Cu9). Mechanical testing indicated a decrease in UTS from 119.05 MPa at HHI to 106.82 MPa at LHI, corresponding to joint efficiencies of 63.32% and 56.82%. Fractography showed brittle failure features at LHI, with cleavage facets and iron-aluminum phases acting as crack initiation sites. Such Al-Cu joints hold considerable importance in electrical applications, such as busbars.