SEM and TEM characterization of the microstructure of post-compressed TiB2/2024Al composite

In the present work, 55 vol.% TiB2/2024Al composites were obtained by pressure infiltration method. Compressive properties of 55 vol.% TiB2/2024Al composite under the strain rates of 10−3 and 1 S−1 at different temperature were measured and microstructure of post-compressed TiB2/2024Al composite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). No trace of Al3Ti compound flake was found. TiB2–Al interface was smooth without significant reaction products, and orientation relationships ([1 1 2¯ 0]TiB2 // [1 1 0]Al and (1 1¯ 0 0)TiB2 // (1¯ 1 1¯)Al) were revealed by HRTEM. Compressive strength of TiB2/2024Al composites decreased with temperature regardless of strain rates. The strain-rate-sensitivity of TiB2/2024Al composites increased with the increasing temperature. Fracture surface of specimens compressed at 25 and 250 °C under 10−3 S−1 were characterized by furrow. Under 10−3 S−1, high density dislocations were formed in Al matrix when compressed at 25 °C and dynamic recrystallization occurred at 250 °C. Segregation of Mg and Cu on the subgrain boundary was also revealed at 550 °C. Dislocations, whose density increased with temperature, were formed in TiB2 particles under 1 S−1. Deformation of composites is affected by matrix, reinforcement and strain rate.

► Interface of particle and Al matrix in TiB2/2024Al was compacted and has no reactant. ► The strain-rate sensitivity of composite increased with the increasing temperature. ► Dislocations transmitted to dynamic recrystallization in Al as temperature increases. ► The strain rate strongly affected the formation of dislocations in TiB2 particles. ► Temperature affected the quantity of dislocations in TiB2 particles.