Microstructure, Corrosion, and Mechanical Properties of Al3102-Alloy Flat Tube Manufactured via Hot Extrusion; [고온 압출 공정으로 제조된 Al3102 합금 납작관의 미세조직, 부식 및 기계적 특성]

초록

This study systematically investigates the microstructure, mechanical, and corrosion properties of hot-extruded Al3102 alloy flat tube, with direct comparisons to as-cast equivalents. Microstructural analysis revealed that both materials primarily consist of an aluminum matrix, with widespread distribution of Al6(Mn,Fe)-type precipitates in their initial structures. The flat tube exhibited an average grain size of 77.3 µm, which is substantially reduced compared to the billet's 243.0 µm, reflecting an effective refinement of the microstructure. Additionally, the flat tube exhibited a slightly lower precipitate volume fraction and a marginally coarser particle size, suggesting that dynamic recrystallization during hot extrusion not only promotes grain refinement but also induces precipitate coarsening. Corrosion resistance was assessed using electrochemical testing procedures based on the ASTM G69 standard. Although the corrosion potentials (Ecorr) of the flat tube (-639.6 mV) and the billet (-657.7 mV) are comparable, the flat tube demonstrated a notably reduced corrosion current density (25.2 µA/cm2) and corrosion rate (0.27 mm/year), implying enhanced resistance to corrosion. This improvement is primarily attributed to the reduced quantity and more homogeneous distribution of precipitates, which effectively suppress galvanic corrosion. In terms of mechanical properties, the flat tube exhibited a marginally greater ultimate tensile strength (UTS) of 91.7 MPa, compared to 77.9 MPa for the billet, presumably due to the Hall–Petch strengthening effect induced by grain refinement. The hot extrusion process enhances the overall performance of Al3102 alloy by tailoring its microstructure and precipitate morphology, thereby providing both theoretical and technical foundations for its application in lightweight systems such as automotive heat exchangers. Copyright © The Korean Institute of Metals and Materials.

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