Measurement and Simulation of Thermal Conductivity of Hafnium-Aluminum Thermal Neutron Absorber Material

Abstract

A metal matrix composite (MMC) material composed of hafnium aluminide (Al 3 Hf) intermetallic particles in an aluminum matrix has been identified as a promising material for fast flux irradiation testing applications. This material can filter thermal neutrons while simultaneously providing high rates of conductive cooling for experiment capsules. The purpose of this work is to investigate effects of Hf-Al material composition and neutron irradiation on thermophysical properties, which were measured before and after irradiation. When performing differential scanning calorimetry (DSC) on the irradiated specimens, a large exotherm corresponding to material annealment was observed. Therefore, a test procedure was developed to perform DSC and laser flash analysis (LFA) to obtain the specific heat and thermal diffusivity of pre-and post-annealment specimens. This paper presents the thermal properties for three states of the MMC material: (1) unirradiated, (2) as-irradiated, and (3) irradiated and annealed. Microstructure-property relationships were obtained for the thermal conductivity. These relationships are useful for designing components from this material to operate in irradiation environments. The ability of this material to effectively conduct heat as a function of temperature, volume fraction Al 3 Hf, radiation damage, and annealing is assessed using the MOOSE suite of computational tools.

Thermomechanical Properties of Neutron Irradiated Al3Hf-Al Thermal Neutron Absorber Materials

“…Interestingly, the three different MMCs underwent almost the same amount of hardening as a function of dose, suggesting that the hardening is not strongly tied to the alteration of the Al 3 Hf dispersion but instead may be due to matrix hardening effects that operate independently of the dispersion. This trend was also observed by Guillen and Harris [ 36 ] for the thermal conductivity of the irradiated material.…”

“…Materials 2023, 16, x FOR PEER REVIEW 9 of 29 independently of the dispersion. This trend was also observed by Guillen and Harris [36] for the thermal conductivity of the irradiated material. Another trend in the data is an increase in the scatter of the hardness data with increasing Al3Hf volume fraction.…”

“…This is true whether the sample was heated to 663 K (390 °C) or 813 K (540 °C) in these subsequent measurements, suggesting that the material is annealing at temperatures below 390 °C. A previous study found, based on exotherms observed during differential scanning calorimetry measurements, that annealing initiates at ~688 K (415 °C) for the specimens irradiated for 3984.6 MWd (3.5–3.9 dpa) [ 36 ]. However, an additional noticeable trend in Figure 18 is the further decrease in observed during the runs to 813 K (540 °C) compared to the runs to 663 K (390 °C).…”

An Algorithm to Generate Synthetic 3D Microstructures from 2D Exemplars

“…Figure 5a illustrates the process of reconstructing a synthetic 3D microstructure of a HfAl 3 -Al metal matrix composite from a segmented 2D optical microsocopy image. 3 The reconstruction algorithm is performed for 100 iterations to generate a reconstructed ''microstructure'' of size 50 Â 50. The progression from the initial randomized reconstruction at the first and 100th iterations of the algorithm is shown in Fig.…”

“…The method described here is much less resource-intensive than obtaining 3D material microstructures by means of electron backscatter diffraction with successive serial sectioning. 3 The first challenge has been addressed with a wide variety of techniques, 4 such as modified Markov Chain Monte Carlo sampling and similar Monte Carlo methods, [5][6][7] and statistical correlation functions, 6,[8][9][10][11] largely in the context of molecular modeling and computational chemistry, and is not explored here. This paper focuses on solutions to the second challenge, namely, digital reconstruction of three-dimensional microstructures.…”