SEM and TEM characterization of the microstructure of post-compressed TiB ₂/2024Al composite

In the present work, 55vol.% TiB ₂/2024Al composites were obtained by pressure infiltration method. Compressive properties of 55vol.% TiB ₂/2024Al composite under the strain rates of 10 ^-3 and 1S ^-1 at different temperature were measured and microstructure of post-compressed TiB ₂/2024Al composite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). No trace of Al ₃Ti compound flake was found. TiB ₂-Al interface was smooth without significant reaction products, and orientation relationships ([1 1 2̄ 0]TiB2 // [1 1 0]Al and (1 1̄ 0 0)TiB2 // (1̄ 1 1̄)Al) were revealed by HRTEM. Compressive strength of TiB ₂/2024Al composites decreased with temperature regardless of strain rates. The strain-rate-sensitivity of TiB ₂/2024Al composites increased with the increasing temperature. Fracture surface of specimens compressed at 25 and 250°C under 10 ^-3S ^-1 were characterized by furrow. Under 10 ^-3S ^-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 TiB ₂ particles under 1S ^-1. Deformation of composites is affected by matrix, reinforcement and strain rate.