The paper focuses on the formation of phase composition, structure, and properties of high-strength aluminum materials that are mechanically alloyed with boron and have a large effective thermal-neutron capture cross-section. A technology based on reactive mechanical alloying is proposed. It is intended to produce dispersion-hardened nanostructured materials in the Al-B system. Structural high-temperature materials with a low density and a great effective thermal-neutron capture cross-section can be obtained by complex alloying of aluminum with elemental boron (up to 40%) and B2O3 (1.5%). When the boron content reaches its maximum (40%), the strength of the material is σt = 380 MPa and σ100500 = 101 MPa; when the boron content decreases to 10%, the strength increases to σt = 560 MPa and σ100500 = 150 MPa.