In-situ DIC study of strain localisation and damage evolution in the B4C-reinforced aluminium metal matrix composite at high temperature

초록

Boron carbide (B4C)-reinforced Al metal matrix composites are suitable materials for spent nuclear fuel (SNF) storage due to the excellent neutron absorption capacity. Mechanical and thermal stability of the neutron absorber materials is required for the dry storage cask at the elevated temperature. Here, we report a study of the strain localisation and damage evolution of the B4C/Al composite at the temperature range from 20 degrees C to 300 degrees C. The strain state in each phase of the B4C/Al composite was investigated by combined optical microscopy and digital image correlation (DIC), electron backscatter diffraction (EBSD) and electron probe micro-analysis (EPMA). The interfacial Ti-B4C/Al layer was characterised by electron channeling contrast imaging (ECCI). The strain distribution transitions from heterogeneous to homogeneous with increasing temperature from 20 degrees C to 300 degrees C. The main failure mode was the B4C particle cracking at 20 degrees C, whilst the strong interfacial bonding and intact B4C particles were found at 150 degrees C and 300 degrees C. At the elevated temperature, the diffusion bonding between the Al-matrix and TiAl products facilitates the stress transfer at the B4C/Al interfaces, thereby reducing the interfacial strain localisation and allowing the B4C reinforcements to accommodate more strain. The loadcarrying capacity of the Al-matrix is reduced by softening effect of DRX. As the result, the Al-matrix was damaged by cracking at 300 degrees C due to the stress redistribution from the fractured B4C particles. The findings in the present study provide a comprehensive understanding of the interfacial stress transfer and damage evolution of the B4C/Al composite at high temperature.

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