Thermal Properties of Mg-B4C Micro and Nanocomposites Fabricated by Static and Dynamic Compaction Methods.

In this study, the effect of the compaction velocity as well as the size and volume content of the reinforcing particles on the thermal properties of Mg-B₄C composites were evaluated. B₄C reinforcing particles at various percentages (0, 5, 10%) and two sizes (micron-scale and nanoscale) were added to the magnesium matrix using a planetary ball mill and compacted at 450 °C and three different compaction velocities. The Instron device was utilized for the quasi-static compaction of the powder particles while a drop-hammer and a Split-Hopkinson bar were used for the dynamic compaction of composite powders at medium and high strain rates, respectively. The thermal behavior of the composites was studied by measuring their thermal conductivity and coefficient of thermal expansion. The results showed improvement in dimensional stability of the composites with increasing the volume percentage of the reinforcing particles. Higher compaction velocities led to higher thermal conductivity and coefficient of thermal expansion. Besides, further addition of the reinforcing particles to the matrix resulted in a decrease in the thermal properties. Magnesium samples reinforced with B₄C nanoparticles exhibited superior thermal properties compared to those reinforced with micron-sized particles. [ABSTRACT FROM AUTHOR]