Files
Alo_15151901_2021.pdf
Open access - Adobe PDF
- 7.48 MB
Details
- Supervisors
- Faculty
- Degree label
- Abstract
- Research interest in high entropy alloys (HEAs) have significantly developed due to the broad possibilities in composition, microstructure and their remarkable properties. Some of these properties include high hardness, high strength and ductility, excellent corrosion and wear resistance. The design concept of this new family of alloys involves the combination of at least five major metallic elements, each of which has a varying atomic percentage, between 5% and 35%. Among the many systems of the HEA family, HEAs containing zinc have shown interesting results in their properties and an improved global performance. Despite their excellent properties, the manufacturing of HEAs brings some additional challenges in comparison to classic alloys based on one single element. Overall, the large difference in melting points and tendency of oxidation of the constitutive elements makes casting of HEAs more complex. Moreover, the high price of HEAs would benefit from a technology that would allow near-net shape products to eliminate costly material waste, thus increasing the overall efficiency of the manufacturing process. Hence other methods such as additive manufacturing or powder metallurgy are being considered for these materials. However, a major challenge in the manufacturing of these HEAs through powder metallurgy is the oxidation of the constitutive elements which diminishes the properties of the resulting alloy. This present Master thesis is focused on the production of a Zinc-based High entropy alloy - FeMnCoNiZn via powder metallurgy. The aim of this study is to avoid oxidation during all stages of the production process. An equimolar FeMnCoNiZn HEA was produced strating from two types of raw powders: i) high purity elemental powders ii) Fe-95Mn - Iron Manganese prealloyed powder and Co, Ni, Zn high purity elemental powders The microstructure was characterized before and after every processing step by SEM, EDX and XRD analysis. Micro-indentation tests were also performed on the sintered samples. The findings indicate that Mn is a critical element for oxidation pick up during the manufacturing process. Even though complete eradication of oxides particles was not achieved in the framework of this project, oxidation can be greatly reduced by the combined use of protective gases such as Ar and H2 and sacrificial metal such as Titanium. Hence, an oxide-free HEA produced via powder metallurgy can be achieved providing that a fundamental understanding of the oxidation reactions occurring during the all process is available.
Citations
Alo, T. (2021). Manufacturing of novel FeMnCoNiZn High entropy alloy via powder metallurgy. https://dial-mem.test.bib.ucl.ac.be/handle/2078.2/25965