TY - JOUR

T1 - Mechanism of low temperature deformation in aluminium alloys

AU - Gruber, Belinda

AU - Weißensteiner, Irmgard

AU - Kremmer, Thomas

AU - Grabner, Florian

AU - Falkinger, Georg

AU - Schökel, Alexander

AU - Spieckermann, Florian

AU - Schäublin, Robin

AU - Uggowitzer, Peter

AU - Pogatscher, Stefan

PY - 2020/8/2

Y1 - 2020/8/2

N2 - This study investigates differences in the deformation mechanisms between room temperature (296 K) and cryogenic temperatures (77 K) and their advantages for low temperature formability in alloys EN AW 1085, EN AW 5182 and EN AW 6016. Compared to room temperature behaviour, tensile tests showed an overall increase in yield strength, ultimate tensile strength and uniform elongation with differences among the principal alloy types. In general, the improved mechanical properties result from higher strain hardening rates at lower temperatures. The application of an extended Kocks-Mecking approach showed a significant reduction of the dynamic recovery and suggested higher dislocation densities upon cryogenic deformation. This was confirmed via in-situ synchrotron experiments, which also reveal a higher proportion of screw dislocations. Moreover, kernel average misorientation maps from electron backscattered diffraction and in-situ cryogenic deformation in a transmission electron microscope displayed a more uniform dislocation arrangement with a reduction of slip lines and less highly misaligned areas after deformation at lower temperatures. Supported by a detailed characterization of the microstructure and its dislocation structure, the associated fundamental mechanisms we reveal, which are at the origin of the exceptional improvement in mechanical properties, are extensively discussed.

AB - This study investigates differences in the deformation mechanisms between room temperature (296 K) and cryogenic temperatures (77 K) and their advantages for low temperature formability in alloys EN AW 1085, EN AW 5182 and EN AW 6016. Compared to room temperature behaviour, tensile tests showed an overall increase in yield strength, ultimate tensile strength and uniform elongation with differences among the principal alloy types. In general, the improved mechanical properties result from higher strain hardening rates at lower temperatures. The application of an extended Kocks-Mecking approach showed a significant reduction of the dynamic recovery and suggested higher dislocation densities upon cryogenic deformation. This was confirmed via in-situ synchrotron experiments, which also reveal a higher proportion of screw dislocations. Moreover, kernel average misorientation maps from electron backscattered diffraction and in-situ cryogenic deformation in a transmission electron microscope displayed a more uniform dislocation arrangement with a reduction of slip lines and less highly misaligned areas after deformation at lower temperatures. Supported by a detailed characterization of the microstructure and its dislocation structure, the associated fundamental mechanisms we reveal, which are at the origin of the exceptional improvement in mechanical properties, are extensively discussed.

UR - http://www.scopus.com/inward/record.url?scp=85089092743&partnerID=8YFLogxK

U2 - doi.org/10.1016/j.msea.2020.139935

DO - doi.org/10.1016/j.msea.2020.139935

M3 - Article

VL - 2020

JO - Materials science and engineering: A, Structural materials: properties, microstructure and processing

JF - Materials science and engineering: A, Structural materials: properties, microstructure and processing

SN - 0921-5093

IS - 795

M1 - 139935

ER -