Creep damage of Al and Al-Sc alloy processed by ECAP

0385920 - ÚFM 2013 RIV SK eng A - Abstract
Král, Petr - Dvořák, Jiří - Kvapilová, Marie - Svoboda, Milan - Sklenička, Václav
Creep damage of Al and Al-Sc alloy processed by ECAP.
Fraktografia 2012. Košice: Institute of Materials Research of the Slovak Academy of Sciences in Košice, 2012 - (Ballóková, B.; Hvizdoš, P.). ISBN 978-80-970964-2-7.
[Fraktografia 2012. 21.10.2012-24.10.2012, Stará Lesná]
R&D Projects: GA ČR GPP108/10/P469
Institutional research plan: CEZ:AV0Z20410507
Keywords : equal-channel angular pressing * creep test * ultrafine-grained materials
Subject RIV: JJ - Other Materials

Experiments were conducted to determine an effect of equal-channel angular pressing (ECAP) on the creep damage and the microstructure of pure aluminium and an Al-Sc alloy. The coarse-grained materials in their as-received states were subjected to ECAP at room temperature using a die, which had a 90° angle between the channels. Creep tests in tension were performed on the as-pressed samples at 473 K under an applied stress range between 10 to 50 MPa. For comparison purposes, some creep tests were performed also on both investigated materials in their as-received states. Following ECAP and creep testing samples were prepared for examination by scanning electron microscopy (SEM) equipped with an electron back scattering diffraction (EBSD) unit. The observation of the free surfaces of the ECAP samples after creep exposure showed the occurrence of mesoscopic shear bands exceeding considerably an average grain size. The formation of these bands could be influenced by inhomogeneity of microstructure created during ECAP. It was observed the cavities and microcracks nucleate and propagate along the mesoscopic shear bands. Their growth and coalescence lead to ductile fracture mode with dimples on the creep fracture surface. The evolution of creep damage and fracture of UFG specimens could be influenced by synergetic effects of grain boundary sliding, formation of shear bands which were oriented along the direction of the last ECAP pass and cavitation.
Permanent Link: http://hdl.handle.net/11104/0215216