"High-temperature Stability and Thermal Expansion Behavior of Equi-atom" by Anilas Karimpilakkal, Joseph W. Newkirk et al.
 

High-temperature Stability and Thermal Expansion Behavior of Equi-atomic Refractory Multi-principal Element Alloys Based on MoNbTi System for Gen IV Reactor Applications

Abstract

The present study investigates the thermal stability and thermal expansion behavior of seven equi-atomic refractory multi-principal element alloys (MPEAs) based on the MoNbTi ternary system composed of low neutron absorption cross section elements. Through an integrated approach utilizing in-situ high-temperature X-ray diffraction (HT-XRD) in conjunction with differential scanning calorimetry (DSC), dilatometry and ageing heat treatment, the thermal stability of the MPEAs was comprehensively analyzed. In-situ HT-XRD experiment confirmed the stability of the room temperature phases up to 1000 °C with no peaks observed corresponding to additional phases in the HT-XRD patterns at 500, 800 and 1100 °C. DSC thermograms showed the absence of peaks up to 1000 °C, while peaks and valleys corresponding to exothermic and endothermic events were observed above 1000 °C. Coefficient of thermal expansion (CTE) derived from second order polynomial fitting of linear thermal expansion data from the dilatometry experiment showed linear increment up to 1000 °C for all the alloys except those containing Zr. The Cr containing alloys exhibited notably higher CTE values, particularly the Al containing alloy exhibited the highest value. Ageing heat treatment at 800 and 1000 °C for 96 h and subsequent microstructural analysis revealed significant precipitation of secondary phases in MoNbTiZr, MoNbTiZrV and MoNbTiCrAl. A substantial increase in hardness was observed in MoNbTiZr and MoNbTiCrAl due to secondary phase precipitation, while the other alloys maintained hardness values comparable to their as-cast and homogenized states.

Department(s)

Materials Science and Engineering

Second Department

Mechanical and Aerospace Engineering

Comments

Idaho Operations Office, U.S. Department of Energy, Grant DE-AC07-05ID14517

Keywords and Phrases

Ageing; Coefficient of thermal expansion (CTE); Differential scanning calorimetry (DSC); Dilatometry; Gen IV reactors; In-situ high-temperature X-ray diffraction (HT-XRD); Multi-principal element alloys (MPEA)

International Standard Serial Number (ISSN)

2213-3917; 0263-4368

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Elsevier, All rights reserved.

Publication Date

01 Apr 2025

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