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Dynamic Compressive Properties of Single Crystal Multi-Principal Element Alloy (MPEA) V₁₀Fe₄₅Co₃₀Cr₁₀Ni₅
Mohamed, Mohamed Yasser Naiem Ahmed
Mohamed, Mohamed Yasser Naiem Ahmed
Date
2024-10
Advisor
Type
Thesis
Degree
Description
A Master of Science thesis in Mechanical Engineering by Mohamed Yasser Naiem Ahmed Mohamed entitled, “Dynamic Compressive Properties of Single Crystal Multi-Principal Element Alloy (MPEA) V₁₀Fe₄₅Co₃₀Cr₁₀Ni₅”, submitted in October 2024. Thesis advisor is Dr. Wael Abuzaid and thesis co-advisor is Dr. Maen Alkhader. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
This thesis investigates the compressive behavior of the single-crystal V₁₀Fe₄₅Co₃₀Cr₁₀Ni₅ high-entropy alloy (HEA) under quasi-static and dynamic loading conditions. The alloy was tested at room temperature (RT: 298 K) for both quasi-static and dynamic loading, and at cryogenic temperature (LN: 77 K) for dynamic loading only. Four crystallographic orientations ([110], [123], [001], and [111]) were studied. The stress-strain behavior and slip system activation were characterized using Digital Image Correlation (DIC) for full-field strain mapping and Electron Backscatter Diffraction (EBSD) for microstructural analysis. Specimens were subjected to quasi-static loading at strain rates of 1.1x10⁻³ to 1.29x10⁻³ s⁻¹, while dynamic tests were conducted at strain rates of approximately 2200 to 3000 s⁻¹ using a Split Hopkinson Pressure Bar (SHPB). The results reveal significant orientation-dependent mechanical properties. Under quasi-static loading at RT, the [111] orientation exhibited the highest yield stress of 197 MPa, while the [001] orientation showed the lowest at 102 MPa. Dynamic loading at RT increased the yield strength across all orientations, with the [111] orientation reaching 305 MPa and [001] reaching 180 MPa. At cryogenic temperatures, the yield strength further increased, with the [111] orientation achieving 448 MPa. Despite the significant increase in strength at cryogenic deformation temperatures, the considered material still exhibited a notable ductile response. Slip-dominated deformation was observed in all orientations. No twinning-induced plasticity (TWIP) or transformation-induced plasticity (TRIP) were observed, indicating that slip was the primary deformation mechanism under all conditions. These findings provide valuable insights into the performance of the V₁₀Fe₄₅Co₃₀Cr₁₀Ni₅ HEA, particularly under high strain-rate and cryogenic conditions.