First observation of a hexagonal close packed metastable intermetallic phase between Cu and Al bilayer films

TY - JOUR

T1 - First observation of a hexagonal close packed metastable intermetallic phase between Cu and Al bilayer films

AU - Cha, L.

AU - Scheu, C.

AU - Richter, G.

AU - Wagner, T.

AU - Sturm, S.

AU - Rühle, M.

PY - 2007/8

Y1 - 2007/8

N2 - In this paper we describe the structure and formation of a new intermetallic phase in the Cu-Al system, which has not been reported before. The phase was found in Cu/Al bilayer films, which were deposited at room temperature on (0001) sapphire substrates using molecular beam epitaxy. The interfacial intermetallic phase is 8 nm thick, and possesses a hexagonal close-packed structure. The lattice parameters of the phase gradually increase from the near-Cu-side to the near-Al-side. In parallel with the described lattice expansion, the chemical composition of the interlayer also varies from 27 to 58 Al at.% from the near-Cu-side to the near-Al-side. The formation and microstructural characteristics of this new phase are explained by Hume-Rothery laws and Shockley partial dislocations. In addition, in-situ heating experiments were performed in a transmission electron microscope at ∼600°C to investigate the thermodynamic stability of this new Cu-Al intermetallic phase. During annealing the intermetallic layer disappears and other known equilibrium intermetallic phases develop. This indicates that this new hexagonal close-packed CuAl intermetallic phase is metastable.

AB - In this paper we describe the structure and formation of a new intermetallic phase in the Cu-Al system, which has not been reported before. The phase was found in Cu/Al bilayer films, which were deposited at room temperature on (0001) sapphire substrates using molecular beam epitaxy. The interfacial intermetallic phase is 8 nm thick, and possesses a hexagonal close-packed structure. The lattice parameters of the phase gradually increase from the near-Cu-side to the near-Al-side. In parallel with the described lattice expansion, the chemical composition of the interlayer also varies from 27 to 58 Al at.% from the near-Cu-side to the near-Al-side. The formation and microstructural characteristics of this new phase are explained by Hume-Rothery laws and Shockley partial dislocations. In addition, in-situ heating experiments were performed in a transmission electron microscope at ∼600°C to investigate the thermodynamic stability of this new Cu-Al intermetallic phase. During annealing the intermetallic layer disappears and other known equilibrium intermetallic phases develop. This indicates that this new hexagonal close-packed CuAl intermetallic phase is metastable.

KW - Al

KW - Cu

KW - Interlayer

KW - Intermetallic phase

KW - TEM

UR - http://www.scopus.com/inward/record.url?scp=34548653484&partnerID=8YFLogxK

U2 - 10.3139/146.101523

DO - 10.3139/146.101523

M3 - 文章

AN - SCOPUS:34548653484

SN - 1862-5282

VL - 98

SP - 692

EP - 699

JO - International Journal of Materials Research

JF - International Journal of Materials Research

IS - 8

ER -