Characterization of Al/B4C composite materials fabricated by powder metallurgy process technique for nuclear applications

Aluminum (Al) matrix composites with boron carbide (B4C) reinforcements were fabricated by solid state powder metallurgy using the hot-pressing process. Composite materials were fabricated at different volume fractions of B4C particles, ranging from 2% to 12%, to evaluate the impact of B4C reinforcements on the thermal and mechanical properties of the composite materials. Thermal properties, such as thermal conductivity (TC) and the coefficient of thermal expansion (CTE), were measured and modeled. The mechanical properties were evaluated by Vickers macro-hardness (HV) and tensile tests to obtain the strain hardening threshold (σy), ultimate tensile stress (UTS), and elongation (A) of the developed composites. Microstructures were observed by scanning electronic microscopy (SEM) and transmission electron microscopy (HRTEM) to show the homogeneity of composites materials with different B4C contents and to characterize the Al/B4C interface. This article shows that incorporating B4C particles until 12% in the Al matrix increased the hardness (+85%) and strain hardening threshold (+55%) of the composite material and decreased the ductility. An increase, up to 8 vol.% B4C, of mechanical properties which a decrease of the elongation at rupture is measured. The strain hardening threshold and the UTS strength increased up to 37% and 13%, respectively. For higher B4C volume fraction, Al/B4C become more brittle leading to very limited plastic phases. Moreover, both the TC and the CTE decreased as a function of the increase of the B4C volume fraction; 20% decrease of TC was measured for an Al/B4C (12 vol.%). The thermal and mechanical properties were correlated with the microstructure of the Al matrix and of the Al-B4C interfacial zone.