Strain-induced grain growth of cryomilled nanocrystalline Al in trimodal composites during forging
Abbreviated Journal Title
Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
Strain-induced grain growth; Nanocrystalline; Al; Trimodal composites; TENSILE PLASTIC-DEFORMATION; BOUNDARY MOTION; NANOSTRUCTURED MATERIALS; THERMAL-STABILITY; ALUMINUM; ALLOY; MECHANISMS; STRENGTH; SIZE; MIGRATION; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering
Grain growth of nanocrystalline aluminum (Al-nc) in trimodal Al metal-matrix-composites (MMCs) during hot forging was investigated. The Al-nc phase formed through cryomilling of inert gas-atomized powders in liquid nitrogen has an average grain size down to 21 nm, exhibits excellent thermal stability. However, substantial grain growth of Al-nc up to 63 nm was observed when the Al MMCs were thermo-mechanically processed even at relatively low temperatures. Grain growth of the cryomilled Al-nc phase in trimodal Al MMCs after hot forging was documented with respect to temperature ranging from 175 degrees C to 287 degrees C, true strain ranging from 0.4 to 135 and strain rate ranging from 0.1 to 0.55 s(-1). Hollow cone dark field imaging technique was employed to provide statistically confident measurements of Al-nc grain size that ranged from 21 to 63 nm. An increase in forging temperature and an increase in true strain were correlated with an increase in grain size of Al-nc. Results were correlated to devise a phenomenological grain growth model for forging that takes strain, strain rate and temperature into consideration. Activation energy for the grain growth during thermo-mechanical hot-forging was determined to be 35 kJ/mol, approximately a quarter of activation energy for bulk diffusion of Al and a half of activation energy for static recrystallization.
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Yao, B.; Simkin, B.; Majumdar, B.; Smith, C.; Van den Bergh, M.; Cho, K.; and Sohn, Youngho, "Strain-induced grain growth of cryomilled nanocrystalline Al in trimodal composites during forging" (2012). Faculty Bibliography 2010s. 3531.