Response of trialuminides to [110] uniaxial loading: An ab initio study for Al3 (Sc,Ti,V)

Autor(en)

Michal Jahnatek, Marian Krajci, Juergen Hafner

Abstrakt

Ab initio density-functional calculations have been used to study the response of trialuminides (Al3Sc, Al3Ti, and Al3V) with the L1(2) and D0(22) crystal structures to uniaxial tensile deformation along [110]. The structures of these intermetallic compounds have a close structural relationship with face-centered-cubic (fcc) metals. The [110] direction is known to be the weak direction of fcc materials under tensile strain, and it is generally accepted that their deformation path is characterized by a "flip-strain" instability which restores the fcc structure after full relaxation by interchanging the [110] and [100] directions. Our aim is to determine whether the response of the L1(2)- and D0(22)-type compounds follows the same scenario. We find that this is not the case. The existence of a lattice-invariant strain implies that the response of the crystal to loading in all active directions ([110], [(1) over bar 10], and [001]) is determined by the same set of interatomic forces. This is evidently the case for fcc metals and applies also to the D0(22) structures, but not to the L1(2) structure where bonding along [110] is based on -TM-Al-bonds (TM means transition metal), whereas -TM-TM-chains exist along the [001]. Consequently, no lattice-invariant strain exists for the L1(2)-type compounds which follow a different deformation path determined by a partially covalent TM-TM (d-d) bonding along [001]. For the D0(22)-type compounds on the other hand, the flip-strain mechanism restores the initial crystal structure. The deformation paths of both types of compounds have been studied from the point of view of phase transformations, providing a detailed atomistic description linked to a quantum-mechanical description of interatomic bonding. We further compare the theoretical strength under [110] tensile strain to the strength calculated for other directions, and we correlate the anisotropy of the limiting strength to the anisotropy of the elastic moduli.

Organisation(en)

Computergestützte Materialphysik

Externe Organisation(en)

Slovenian Academy of Sciences and Arts

Journal

Physical Review B

Band

76

Anzahl der Seiten

19

ISSN

1098-0121

DOI

https://doi.org/10.1103/PhysRevB.76.014110

Publikationsdatum

2007

Peer-reviewed

Ja

ÖFOS 2012

103015 Kondensierte Materie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/4ff1cd4b-3a0b-40a9-87da-c7f04dd7a69e