Strengthening mechanisms of mechanical properties in Mg−B4C composites fabricated by powder metallurgy method

The influence of the volume fraction of B 4 C nanoparticles (B 4 C np ) on the mechanical properties of Mg−B 4 C composites was investigated. Mg− x B 4 C ( x =5 and 7 vol.%) composites were fabricated via low-energy ball milling, spark plasma sintering (SPS), and hot extrusion. The Mg−5vol.%B 4 C composite exhibited a Young’s modulus of 55.2 GPa, indicating a 23.5% increment over that of pure Mg and in good agreement with the results from the Hashin−Shtrikman (H−S) model. However, a higher B 4 C np content reduced the efficiency of modulus enhancement due to nanoparticle agglomeration and interfacial reaction. The Mg−5vol.%B 4 C composite also achieved yield strength and ultimate tensile strength improvements of 16.8% and 9.1%, respectively. Quantitative analysis indicated that thermal mismatch strengthening was the dominant strengthening mechanism, while both thermal mismatch strengthening and Orowan strengthening showed size-dependent behavior linked to nanoparticle clustering.