MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al -TiB₂ PARTICLE REINFORCED COMPOSITES PROCESSED BY SPARK PLASMA SINTERING

Particle reinforced metal matrix composites display a unique combination of mechanical properties and may be used in a wide range of applications. In the present work, the microstructure and mechanical properties of Al matrix composites with various volume fraction of TiB₂ particles were investigated. The composites were fabricated by SPS from TiB₂ +Al powders mixtures. The average particle size was about 2 and 40 μm for TiB₂ and Al powders, respectively. The volume fraction of the ceramic particles varied from 0 to 15%. Fully dense composites with homogeneously distributed ceramic particles were sintered at 550°C under 80MPa uniaxial pressure. TiB₂ particles are mostly located at the grain boundaries in the Al matrix. XRD analysis confirmed the presence of two phases with no evidence of new phases formed during the sintering process. The hardness value only slightly increased with increasing ceramic volume fraction and was about 37 HV. Compressive test was conducted on samples with 10 mm diameter and 20 mm hight. Finite element analyses were used in an iterative process to determine the effective stress-strain curves as a function of TiB₂ volume fraction. The compressive yield stress increased with increasing TiB₂ volume fraction up to 10%, while composites with 15%vol TiB₂ shows a slight decrease in the yield stress. The strain hardening coefficient also decreased with increasing TiB₂ volume fraction. Different fracture modes depending on the volume fraction of the TiB₂ were observed. The fracture mode of the composite with 15% of TiB₂ display completely brittle behavior.