Deformation behavior of pure aluminum at room and cryogenic temperatures

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 <111> 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.