Date of Award

2024-05-01

Degree Name

Master of Science

Department

Metallurgical and Materials Engineering

Advisor(s)

Stella A. Quinones

Abstract

In this study, the AlCuNiMn and AlCuNiMnSi high entropy alloys (HEAs) are investigated to characterize the effect of Si addition and subsequent annealing treatments on the corrosion behavior in a 3.5wt% NaCl solution at room temperature. The microstructure evolution from the as-received condition and after annealing at 600°C, 800°C, and 1000°C for 24 hours in air is examined. The microstructural transformation of HEAs is extensively reported in the literature. However, its impact on the corrosion resistance of HEAs has not received the same attention. In this study, an increase in the annealing temperature of the base AlCuNiMn alloy improved the corrosion resistance due to element redistribution and homogenization of the microstructure. Annealing resulted in the appearance of new microconstituents with a higher resistance to corrosion compared to the alloy in the as-received condition. Introducing Si to the AlCuNiMn alloy system enhances the corrosion resistance. The addition of Si alters the morphology of the microstructure in three noticeable ways: 1) a redistribution of the other four elements, 2) the appearance of a new MnSi-rich microconstituent, and 3) a decrease in the size of voids. The results indicate that the AlCuNiMnSi alloy in the as-received condition is the superior alloy compared to the base AlCuNiMn alloy as it possesses the best corrosion resistance to the 3.5wt% NaCl solution. The presence of the Ni-rich microconstituent with small traces of Si slows the dissolution rate of the alloy. However, the phase fraction of Ni begins to dwindle then dissipates when the annealing temperature is increased to 800°C, leading to a slight increase in the corrosion rate.

Language

en

Provenance

Received from ProQuest

File Size

82 p.

File Format

application/pdf

Rights Holder

Celine Chiong

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