The enhanced superplasticity of a 2024 matrix nanocomposite reinforced by TiC particles

Fine grains less than 10 pm are usually the prerequisite to superplasticity of alloys. Traditionally, multiple-step rolling and heat treatment are necessary to obtain fine grain microstructure of Al alloys. In this paper, a simple method to achieve superplasticity for 2024 alloys has been proposed. An inhomogeneous 2024-1.5TiC nanocomposite reinforced by TiC threadiness arrays was fabricated via casting and hot extrusion processes. By subsequent annealing, fine alpha-Al grains with average size of 4.1 mu m were obtained. And then, elongation of 405% for the 2024-1.5TiC was achieved at 485 degrees C with initial strain rate of 3.33 x 10(-4) s(-1). According to experimental and theoretical analysis, the deformation is mainly controlled by grain boundary sliding and dislocation slip mechanisms. It was found that TiC nanoparticles accelerated nucleation of alpha-Al recrystallization during annealing, and the limited space between adjacent TiC threadiness arrays restricted alpha-Al grain growth. The high nucleation rate and low grain growth rate resulted in the formation of fine grains. Besides, TiC nanoparticles inhibited dynamic grain growth during tensile deformation, which also contributes to the superplasticity.