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<p>Aluminium alloys especially grade 6061 are mostly employed in various challenging industries like aerospace, automotive, pressure vessels, and various general-purpose construction works. This grade is also known as commercial grade. 6061 alloy shows good response to heat treatment. The grain size of primary phase and distribution of secondary phase is highly affected by heat treatment processes. The present work deals with heat treatment of Al6061 alloy by employing solution annealing at 400&#xa0;°C for 4&#xa0;h followed by water quenching and an addition heating for 5&#xa0;h followed by cooling into three different media. The properties of heat-treated samples were compared and analysed on the basis of properties shown by the ‘as received’ sample. Two destructive mechanical tests, such as, tensile test and compression have been done in this work. Additionally, the optical microscopy, fractography, and X-ray diffraction were also performed to analyse the microstructural attributes of the samples. Microstructural analysis revealed an α-Al matrix with Mg₂Si and Fe-rich intermetallic phases. Heat-treated samples exhibited finer precipitate dispersion compared to the as-received sample, though aging at 300&#xa0;°C promoted coarse precipitate formation, reducing strength but enhancing ductility. XRD confirmed dominant Al peaks with minor Mg₂Si phases. Tensile test results showed significant reductions in yield strength (≈58%) and ultimate tensile strength (≈55%) for heat-treated samples relative to the as-received condition, while elongation increased by up to 109%, indicating improved ductility. Compression tests demonstrated superior strain hardening and ultimate compressive strength (≈483&#xa0;MPa) for the as-received sample, whereas heat-treated specimens exhibited lower strength (≈263–271&#xa0;MPa) but comparable compressive ductility. Fractography revealed ductile fracture features in heat-treated samples versus mixed-mode fracture in the as-received condition. Unlike conventional studies focusing on single-stage aging or standard quenching, this work uniquely investigates a dual thermal cycle (solution annealing followed by high-temperature aging) combined with three distinct cooling media (water, oil, and air), providing new insights into how cooling-rate variations influence precipitate characteristics, ductility, and strength in Al-6061 alloy.</p>

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Effect of Two Step Thermal Exposure on microstructure, Compressive Strength, Tensile Strength of Al-6061 Alloy

  • 期刊论文

  • 发表日期：

    2026年4月21日

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  • Tejas Kukreja,
  • Ketan Verma,
  • Ayan Khan,
  • Saurabh Dewangan

摘要

Aluminium alloys especially grade 6061 are mostly employed in various challenging industries like aerospace, automotive, pressure vessels, and various general-purpose construction works. This grade is also known as commercial grade. 6061 alloy shows good response to heat treatment. The grain size of primary phase and distribution of secondary phase is highly affected by heat treatment processes. The present work deals with heat treatment of Al6061 alloy by employing solution annealing at 400 °C for 4 h followed by water quenching and an addition heating for 5 h followed by cooling into three different media. The properties of heat-treated samples were compared and analysed on the basis of properties shown by the ‘as received’ sample. Two destructive mechanical tests, such as, tensile test and compression have been done in this work. Additionally, the optical microscopy, fractography, and X-ray diffraction were also performed to analyse the microstructural attributes of the samples. Microstructural analysis revealed an α-Al matrix with Mg₂Si and Fe-rich intermetallic phases. Heat-treated samples exhibited finer precipitate dispersion compared to the as-received sample, though aging at 300 °C promoted coarse precipitate formation, reducing strength but enhancing ductility. XRD confirmed dominant Al peaks with minor Mg₂Si phases. Tensile test results showed significant reductions in yield strength (≈58%) and ultimate tensile strength (≈55%) for heat-treated samples relative to the as-received condition, while elongation increased by up to 109%, indicating improved ductility. Compression tests demonstrated superior strain hardening and ultimate compressive strength (≈483 MPa) for the as-received sample, whereas heat-treated specimens exhibited lower strength (≈263–271 MPa) but comparable compressive ductility. Fractography revealed ductile fracture features in heat-treated samples versus mixed-mode fracture in the as-received condition. Unlike conventional studies focusing on single-stage aging or standard quenching, this work uniquely investigates a dual thermal cycle (solution annealing followed by high-temperature aging) combined with three distinct cooling media (water, oil, and air), providing new insights into how cooling-rate variations influence precipitate characteristics, ductility, and strength in Al-6061 alloy.