Synthesis and mechanical behavior of nanostructured Al 5083/n-TiB2 metal matrix composites

Nanostructured Al 5083-based composites with nano-TiB2 reinforcement particles were fabricated via cryomilling and spark plasma sintering (SPS). TEM observation revealed that the Al matrix consists of equiaxed nano-grains (average size, ∼74 nm), and the reinforcement, TiB2 nanoparticles (n-TiB2), was distributed discretely and homogeneously in the Al matrix. The interface between the Al-matrix and n-TiB2 appears to be free of defects, and no obvious discontinuities were observed. The composite exhibits a compressive strength of 817 MPa with 6.0% strain-to-failure. The strength is 20% higher than that of an equivalent SPS consolidated Al 5083 without reinforcement. Nanoindentation was used in our study to provide fundamental insight into the local microscopic mechanical properties. The strengthening mechanisms of the composites are analyzed taking into account the grain boundaries, the Orowan strengthening from the n-TiB2 particles and dispersoids such as Al2O3, AlN and Al6Mn, as well as geometrically necessary dislocations induced in the matrix by the nano-TiB2 particles.