Effects of Grain Refinement by ECAP on the Deformation Resistance of\nAl Interpreted in Terms of Boundary-Mediated Processes

0468252 - ÚFM 2017 RIV NL eng J - Journal Article
Blum, W. - Dvořák, Jiří - Král, Petr - Eisenlohr, P. - Sklenička, Václav
Effects of Grain Refinement by ECAP on the Deformation Resistance of
Al Interpreted in Terms of Boundary-Mediated Processes.
Journal of Materials Science & Technology. Roč. 32, č. 12 (2016), s. 1309-1320. ISSN 1005-0302
R&D Projects: GA MŠMT(CZ) ED1.1.00/02.0068
Institutional support: RVO:68081723
Keywords : Deformation * Grain boundaries * Equal channel angular pressing (ECAP) * Creep * Dynamic recovery * Fine grained microstructure
Subject RIV: JG - Metallurgy
Impact factor: 2.764, year: 2016

Results of a large set of tensile and compressive creep tests on pure Al were reanalyzed for the influence
of low- and high-angle grain boundaries on the deformation resistance at the temperature
T = 473 K = 0.51Tm where Tm is the melting point. Thermomechanical treatment by equal channel angular
pressing followed by heating to T led to strong increase of areal fraction of high-angle boundaries in a
structure of subgrains of ≈10−6 m in size, accompanied by significant reduction of subgrain strengthening
and of the stress sensitivity of the deformation rate. (Sub)grain strengthening by low-angle boundaries
is most effective; the strengthening effect virtually disappears during creep as the boundary spacings
coarsen toward their stress-dependent, quasi-stationary size wqs. The same type of coarsening is found
for (sub)grain structures with large fraction of high-angle boundaries; in the quasi-stationary state they
lead to softening at low and strengthening at high stresses, and a significant increase in tensile fracture
strain to values up to 0.8. The results are analogous to former results for Cu and are explained in the
same way by the influence of boundaries on storage and recovery of crystal defects and the homogenization
of glide.
Permanent Link: http://hdl.handle.net/11104/0266116