Investigation of superplasticity and dynamic grain growth in ultrafine-grained Al–0.5%Mg–Sc alloys

Investigation of Effect of Preliminary Annealing on Superplasticity of Ultrafine-Grained Conductor Aluminum Alloys Al-0.5%Mg-Sc

“…The present papers were aimed at an additional verification of the hypothesis proposed in [ 30 ] on the effect of the Al 3 Sc particles on the superplastic characteristics of the UFG Al-0.5%Mg-Sc alloys. Note that the intermittent decomposition of solid solution leads to the formation of large dashed linewise Al 3 (REE,TM) incoherent particles at the grain boundaries in the Al alloys (see [ 30 , 39 , 40 ]). It may lead to an increased number of failures of the small-sized wires of 0.2–0.3 mm in diameter in the course of fabrication by drawing, rolling, or extraction.…”

“…The Al alloys microalloyed with additives of rare earth elements (REEs) and of transition metals (TMs)–Sc, Zr, Hf, etc., are promising conductor materials [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Nucleation of Al 3 (REE,TM) nanoparticles with Ll 2 structure allows providing a high level of the thermal stability of the ultrafine-grained (UFG) microstructure in the severely deformed Al alloys [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ] and, as a consequence, high superplastic characteristics of these ones [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The studies on the superplasticity characteristics of the UFG conductor aluminum alloys with ultra-low Mg content are almost absent.…”

“…It was shown in [ 30 ] that intensive pore formation in the Al 3 Sc incoherent particles may be one of the factors limiting the ultimate superplastic characteristics of the UFG Al-0.5%Mg-Sc alloys. It should be stressed here that the formation of the Al 3 Sc particles in the investigated UFG alloys at reduced temperatures goes via a discontinuous precipitation mechanism (see [ 4 , 30 , 38 ]) similar to the low-temperature discontinuous solid solution decomposition in Al-Zr alloys [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ].…”

“…As it has been shown in [ 44 , 45 ], at certain critical power ω *, the excess energy of the disclination loop becomes so high that it becomes energetically favorable for the grain boundary to “release” from the source of this latent energy. At the elevated test temperatures, such a “relaxation” of the accumulated energy may take place through the micropore formation at the interphase boundaries “Al 3 Sc particle–Al” [ 30 ]. In the course of the superplastic deformation, such micropores can become the origins of cavitation fractures in the UFG Al-0.5%Mg-Sc alloys [ 30 ].…”

“…At the elevated test temperatures, such a “relaxation” of the accumulated energy may take place through the micropore formation at the interphase boundaries “Al 3 Sc particle–Al” [ 30 ]. In the course of the superplastic deformation, such micropores can become the origins of cavitation fractures in the UFG Al-0.5%Mg-Sc alloys [ 30 ].…”