De Jesús López, Manny Xavier
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Publication Effects of Mg and Si additions to novel Al-Ce based alloys for aerospace applications(2020-07-24) De Jesús López, Manny Xavier; Suárez, O. Marcelo; College of Engineering; Calcagno, Barbara O.; Quintero, Pedro O.; Department of Materials Science and Engineering; Sundaram, Paul A.The experimental work in this thesis is focused on the alloying effects of Mg and Si in Al-Ce base alloys. The alloys were gravity cast over a 20-point (or target chemical compositions) test matrix. X-ray diffraction, optical microscopy, Vickers hardness, density determination, and thermogravimetric analysis paired with differential thermal analysis were the characterization methods of choice. The outcomes correlate the effects of the phases present with thermal properties, hardness, and density. The Al-Ce eutectic is used as the groundwork in assessing the effects of Mg and Si on the phases present, thermal properties, hardness, and density. The experimentation revealed that: 1) adding Mg to the eutectic increases hardness, reduces density, and lowers the alloy melting temperature, 2) adding Si to the eutectic promotes the formation of τ1 phase formation and brings down the melting temperature, 3) alloying the eutectic with both Mg and Si hardened the alloys, lowered density, and kept melting temperatures near 580 °C. Alloy hardening was studied through a 10-hour T4 heat treatment and a melt and quench sequence. Both the T4 and M&Q heat treatments confirmed that the strengthening mechanism in the Al-Ce-Mg and Al-Ce-Mg-Si alloys is responsive to increments in Mg levels. The T4 heat treatment revealed the dissolution of the τ1 phase and formation of τ2. The latter led to quantification of the diffusivity of Si for the dissolution rate of τ1 in Al-Ce-Mg-Si alloys.