Deformation behavior of pure aluminum at room and cryogenic temperatures

Abstract

The deformation behavior of the pure aluminum has been studied at 298 K and 77 K to elucidate the mechanism for dual-enhancement effect at cryogenic temperature. The results reveal that as the deformation temperature decreases from 298 K to 77 K, the tensile strength and elongation increase from 67.9 MPa to 49.1% to 142.4 MPa and 61.9%, respectively. The simultaneous increase in strength and ductility at 77 K is attributed to the higher strain hardening rate and more uniform deformation at cryogenic temperature. Results obtained from quasi in-situ EBSD indicate that at cryogenic temperatures, there is a higher density of dislocations that are uniformly distributed within the grains. It helps alleviate dislocation pile-ups and reduces the likelihood of crack initiation at grain boundaries. Moreover, a significant number of grains align their orientation rotation towards at cryogenic temperature. Multiple fine slip systems initiate within these grains, contributing to improved mechanical properties in pure aluminum. In contrast, samples deformed at 298 K exhibit localized strain during deformation, with the initiation of unfavorable, non-uniform coarse slip bands within the grains. The findings of this study offer insights into the mechanisms of the dual-enhancement effect in pure aluminum at cryogenic temperatures.

Keywords

• Pure aluminum
• Cryogenic temperature
• Microstructure evolution
• Plastic deformation