Temperature dependence of dislocation structure of L12–Al3Sc

Creep properties of Al3Sc and Al3(Sc, X) intermetallics

“…X-ray di raction from powder specimens con®rmed that the binary Al 3 Sc has the L1 2 structure with a lattice parameter a = 4.1026(7) A Ê , in good agreement with previous results [9]. The bulk composition was 74.8 at.%Al±25.2 at.%Sc as measured by wet chemical analysis.…”

“…Schneibel et al [10], however, found that polycrystalline Al 3 Sc is brittle, with a relatively low yield stress increasing with temperature from 77 to 500 K. Fracture was found to occur in a transgranular manner by cleavage, primarily on {011} planes. The phenomena of anomalous yield stress was also observed by Fukunaga et al [9]. The increasing need for aluminum alloys with good creep resistance at high homologous temperatures has intensi®ed the search for alloying elements producing ®ne, stable precipitates [11].…”

“…Intermetallics with the L1 2 structure are expected to deform plastically by the generation, motion and multiplication of h110i superdislocations on {111} planes. In fact, Fukunaga et al [9] reported that superdislocations in Al 3 Sc dissociate into two a/3h112i superpartials separated by a superlattice intrinsic stacking fault at room temperatures. Schneibel et al [10], however, found that polycrystalline Al 3 Sc is brittle, with a relatively low yield stress increasing with temperature from 77 to 500 K. Fracture was found to occur in a transgranular manner by cleavage, primarily on {011} planes.…”

“…At elevated temperatures where the Al 3 Sc precipitates are sheared, the creep properties of the Al 3 Sc phase dictate those of the alloy. Little research has however been performed on the mechanical properties of the pure Al 3 Sc phase [1,9,10,14,15]. In particular, despite potential high-temperature applications for Al 3 Sc as precipitates in aluminum alloys or in bulk form, the high-temperature mechanical properties of Al 3 Sc are almost unexplored, with the exception of Refs [9] and [15] who measured stress±strain curves in the range 77±1073 K and Ref.…”

“…Little research has however been performed on the mechanical properties of the pure Al 3 Sc phase [1,9,10,14,15]. In particular, despite potential high-temperature applications for Al 3 Sc as precipitates in aluminum alloys or in bulk form, the high-temperature mechanical properties of Al 3 Sc are almost unexplored, with the exception of Refs [9] and [15] who measured stress±strain curves in the range 77±1073 K and Ref. [16] who reported microhardness and elastic modulus from 298 to 773 K. The purpose of the present study is to determine, for the ®rst time, the general characteristics of creep deformation for the binary Al 3 Sc and ternary Al 3 (Sc, X ), where scandium is replaced by di erent transition elements.…”