Comparative study of Al-TiAl composites with different intermetallic volume fractions and particle sizes

A new family of Al-matrix composites containing γ-TiAl intermetallic reinforcement particles has been processed by extruding aluminium and TiAl powders in different proportions up to 50% of the intermetallic. To modify the size and distribution of the intermetallic powders they were used in three different states, namely, atomised, and milled for 1 and 5 h. The yield strengths of the composites are very dependent on the volume fraction of the reinforcement and follow a Hall-Petch type relationship on the interparticle spacing. Much of the strength of the composites is retained up to temperatures of 250 °C, with an activation energy responsible for the deformation process measured as Q=96±5 kJ/mol for all materials, indicating that the high temperature deformation is controlled by diffusion along dislocations in the aluminium matrix. The plastic ductility is also dependent on the volume fraction of particles but is not much affected by the particle state. The composites containing 25% particles have higher ductilities, ranging between 9 and 12% at all temperatures and for all particle states.