Abstract:The potential of powder metallurgy processing for the manufacture of Al-SrB₆ composites was explored. Al₄Sr particles fractured extensively during the ball milling of Al-15Sr/Al-4B powder mixtures. There was no interaction between the Al₄Sr and AlB₂ compounds across the section of the aluminium grains in the as-milled state. SrB₆ formed, when the ball milled powder blends were subsequently annealed at sufficiently high temperatures. Ball milling for 1 h was sufficient for SrB₆ to become the major constituent in powder blends annealed at 700 °C while it took 2 h of ball milling for powder blends annealed at 600 °C. Higher annealing temperatures and longer ball milling time encouraged the formation of the SrB₆ compound while the latter made a great impact on the microstructural features of the Al-SrB₆ composite. The SrB₆ compound particles were much smaller and more uniformly distributed across the aluminium matrix grains in powder grains ball milled for 2 h before the annealing treatments at 600 °C and 700 °C.

Key words: Al-SrB₆ composites; strontium hexaboride; ball milling; powder metallurgy processing