NSUF 17-1028: Microstructural Examination of Neutron Irradiated Al-HfAl3 Metal Matrix Composite Materials for Application to Neutron Spectrum Modification in Nuclear Reactors

Al-HfAl3 metal matrix composite (MMC) materials are under consideration for use as a thermal neutron absorber material (due to the Hf) in water cooled nuclear reactors to locally generate a fast neutron spectrum to support fast neutron reactor core materials development. Specimens made from Al-HfAl3 MMC materials at three different dispersion levels were irradiated in ATR at ~70°C to four dose levels ranging from ~0.5-4 dpa. Among these are tensile specimens that were tested at PNNL (and currently reside at PNNL) and other specimens that were tested at INL to determine coefficient of thermal expansion and thermal conductivity. In order to obtain a comprehensive understanding of the viability of this material, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are proposed be conducted on unirradiated and irradiated materials to characterize the deformation response at the microstructural level and to better predict the expected lifetime of this material for its proposed purpose. SEM will be used to document the larger scale deformation modes of tensile tested specimens, the fracture behavior (if any) of the HfAl3 particles, and the strength of the Al-HfAl3 interface. TEM will be used to observe nanometer scale changes in microstructure including Si precipitation, void swelling, and the possible existence of nanometer size HfAl3 precipitates resulting from ballistic dissolution of the large HfAl3 particles. It will also be used to study the Al-HfAl3 interface more closely, and examine the relationship between dislocation movement and the microstructure. Chemical analyses by SEM and TEM will be used to augment understanding of the material response to irradiation. The results of these examinations will provide input into whether one of the alloys is sufficient, or whether a revised alloy is required. Six months are needed for this work.

Additional Info

Field	Value
Abstract	Al-HfAl3 metal matrix composite (MMC) materials are under consideration for use as a thermal neutron absorber material (due to the Hf) in water cooled nuclear reactors to locally generate a fast neutron spectrum to support fast neutron reactor core materials development. Specimens made from Al-HfAl3 MMC materials at three different dispersion levels were irradiated in ATR at ~70°C to four dose levels ranging from ~0.5-4 dpa. Among these are tensile specimens that were tested at PNNL (and currently reside at PNNL) and other specimens that were tested at INL to determine coefficient of thermal expansion and thermal conductivity. In order to obtain a comprehensive understanding of the viability of this material, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are proposed be conducted on unirradiated and irradiated materials to characterize the deformation response at the microstructural level and to better predict the expected lifetime of this material for its proposed purpose. SEM will be used to document the larger scale deformation modes of tensile tested specimens, the fracture behavior (if any) of the HfAl3 particles, and the strength of the Al-HfAl3 interface. TEM will be used to observe nanometer scale changes in microstructure including Si precipitation, void swelling, and the possible existence of nanometer size HfAl3 precipitates resulting from ballistic dissolution of the large HfAl3 particles. It will also be used to study the Al-HfAl3 interface more closely, and examine the relationship between dislocation movement and the microstructure. Chemical analyses by SEM and TEM will be used to augment understanding of the material response to irradiation. The results of these examinations will provide input into whether one of the alloys is sufficient, or whether a revised alloy is required. Six months are needed for this work.
Award Announced Date	2017-09-20T12:37:33.99
Awarded Institution	Center for Advanced Energy Studies
Facility	Microscopy and Characterization Suite
Facility Tech Lead	Stuart Maloy, Yaqiao Wu
Irradiation Facility	None
PI	Yuanyuan Zhu
PI Email	[email protected]
Project Type	RTE
RTE Number	1028