Effects of yttrium addition and aging on mechanical properties of AA2024 fabricated through multi-step stir casting
(1. Metallurgical and Materials Engineering Department, Indian Institute of Technology Roorkee - 247667, India;
2. Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee - 247667, India)
2. Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee - 247667, India)
Abstract: The effects of yttrium and artificial aging on AA2024 alloy were investigated. The developed samples were further subjected to artificial aging at 190 °C for 1-10 h with an interval of 1 h. The metallurgical characterization was done by scanning electron microscope and X-ray diffraction. The mechanical characterization like hardness and tensile strength of the samples was done using computerized Vickers hardness testing machine and universal testing machine. The microstructures revealed that addition of yttrium refined the α(Al) matrix and led to the formation of Al-Cu-Y intermetallic in the shape of Chinese script which strengthened the samples. Compared to the base metal, samples with yttrium addition showed better mechanical properties. The sample reinforced with 0.3 wt.% yttrium showed the highest mechanical properties with the hardness of 66 HV, UTS of 223 MPa, YS of 180 MPa, and elongation of 20.9%. The artificially aged samples showed that the peak hardening of all the samples took place within 5 h of aging at 190 °C with Al2Cu precipitation. Aging changed the intermetallic from Chinese script to the fibrous form. The optimum amount of yttrium addition to AA2024 was found to be 0.3 wt.%.
Key words: yttrium; artificial aging; mechanical properties; multi-step stir casting; precipitation; microstructure characterization