Document Type : Research Article
Authors
1
Assistant Professor, Department of Mechanical Engineering, Ramaiah Institute of Technology, Bangalore, India, 560054.
2
Research Scholar, Department of Mechanical Engineering, Ramaiah Institute of Technology, Bangalore, 560054, India.
3
Associate Professor, Department of Mechanical Engineering, Ramaiah Institute of Technology, Bangalore, India, 560054.
4
Aircraft Research and Design Centre, HAL, Bangalore, India
5
Professor (Research Consultant or Mentor), Department of Mechanical Engineering, Sambhram Institute of Technology, Bangalore, India, 560097.
Abstract
Micro-alloying with nickel can enhance these properties and improve the coefficient of thermal expansion. This study investigates the influence of nickel on the microstructural and thermal expansion characteristics of AA2024 and AA7175 aluminium alloys, both commonly used in aerospace. AA2024 primarily contains copper, while AA7175 has zinc; both are heat-treatable and possess excellent strength. In this research, alloys were stir-cast with varying percentages of nickel and 0.2% strontium, which improves grain structure. The alloys were homogenized at 480°C for 15 hours, quenched in water, and subjected to tensile testing, EDS, XRD, microstructural and thermal expansion analyses. Results showed that nickel addition increased strength to 215 MPa for AA2024 and 284 MPa for AA7175 with 5% nickel. XRD and EDS revealed the formation of intermetallic compounds like Al2Ni3, Al3Ni, and Al3NiCu. However, increasing nickel beyond 5% led to undesirable needle-like structures. Thermal expansion studies indicated a reduction in the coefficient of linear thermal expansion by 14.1% for AA2024 and 16.5% for AA7175 with 2% nickel, reducing thermal stress under loading up to 350°C.
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