Design and Development of Novel Equiatomic Refractory Multi Principal Elemental Alloys Based on Monbti System for use in Irradiation Environments

Author

Anilas Karimpilakkal, Missouri University of Science and Technology

Keywords and Phrases

CALPHAD; Gen IV reactor; High entropy alloys; Multi principal elemental alloys; phase stability; radiation resistance

Abstract

"Multi Principal Elemental Alloys (MPEA) have emerged as promising materials for next-generation nuclear reactors due to their exceptional irradiation resistance. Eight equiatomic MPEA based on the MoNbTi system, comprising of elements with low thermal neutron absorption cross-sections were explored using a combined approach employing empirical parameter estimations, and CALPHAD simulations by which the phases and elemental segregation observed in all the alloys in the as-cast state were predicted. Solution heat treatment at 1500°C transformed five alloys into single-phase matrix materials, enhancing homogeneity and reducing hardness. The densities of the alloys ranged between 6.47 to 7.68 g/cm³, hardness between 472 and 656 VHN, Young’s modulus between 142 GPa to 169 GPa, shear modulus between 54 GPa and 62 GPa, bulk modulus between 117 GPa to 194 GPa and Poisson’s ratio between 0.3 to 0.35. The in-situ high temperature Xray diffraction results, differential scanning calorimetry and dilatometry results up to 1000°C suggested the high temperature phase stability of the MPEA. Subsequent ageing heat treatment at 800 and 1000 oC for 96 hours revealed significant secondary phase precipitation in MoNbTiZr, MoNbTiZrV, and MoNbTiCrA. Oxidation studies at 800 oC for 24 hours in air revealed superior oxidation resistance and cubic rate law dependence in Cr containing MPEA especially in MoNbTiCrAl, while severe mass gain resulting in total disintegration and exfoliation in MoNbTiZr and MoNbTiZrV. This comprehensive study underscores the potential of novel MPEA as promising materials for advanced nuclear reactor applications, shedding light on their microstructural control, mechanical properties, thermal stability, and oxidation resistance"-- Abstract, p. iv

Advisor(s)

Newkirk, Joseph William

Committee Member(s)

Emdadi, Arezoo
Liou, Frank W.
Wen, Haiming
Bartlett, Laura

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2025

Journal article titles appearing in thesis/dissertation

Paper I, found on pages 59–89, is intended for submission to Nuclear Engineering and Design Journal.

Paper II, found on pages 90–125, is intended for submission to Journal of Nuclear Materials.

Paper III, found on pages 126–153, is intended for submission to International Journal of Refractory Metals and Hard Materials.

Paper IV, found on pages 154–180, is intended for submission to Corrosion Science Journal

Pagination

xviii, 210 pages

Note about bibliography

Includes_bibliographical_references_(pages 194-209)

Rights

© 2024 Anilas Karimpilakkal , All Rights Reserved

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Thesis Number

T 12492

Recommended Citation

Karimpilakkal, Anilas, "Design and Development of Novel Equiatomic Refractory Multi Principal Elemental Alloys Based on Monbti System for use in Irradiation Environments" (2025). Doctoral Dissertations. 3391.
https://scholarsmine.mst.edu/doctoral_dissertations/3391