Continuous Precipitation 上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Transition phases-0" 0":Tetragonal unit cell,essentially a distorted fcc structure Cu and Al atoms ordered on (001)planes Fully coherent plate-like precipitates with a (001)habit plane OR:(001)g(001)a [100l[100. (CAl.●Cu) 450. (001i (010】 100) -404A 404A All s sides coherent a-matrix -404A 404A K.Chen 11
K. Chen Continuous Precipitation 11 Transition phases – θ’’ θ’’ : Tetragonal unit cell, essentially a distorted fcc structure Cu and Al atoms ordered on (001) planes Fully coherent plate-like precipitates with a {001}α habit plane OR:
Continuous Precipitation 上浒充通大兽 SHANGHAI JIAO TONG UNIVERSITY Transition phases-0" Visible through the coherency-strain fields caused by the misfit strain by the misfit perpendicular to the plates Size:up to ~10 nm thick and 100 nm in diameter Viewing direction of the figure? 0-25μ X63000 K.Chen 12
K. Chen Continuous Precipitation 12 Transition phases – θ’’ Visible through the coherency-strain fields caused by the misfit strain by the misfit perpendicular to the plates Size: up to ~10 nm thick and 100 nm in diameter X 63000 Viewing direction of the figure?
Continuous Precipitation 上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Transition phases-0' 0':Tetragonal unit cell with an approximate composition CuAl2 (001)planes identical with (001) (100)and(010)planes have diff.crystal structure to the matrix>large misfit in the [001]direction Forms as plates on (001)with the same orientation relationship as 0" Fully coherent broad faces of the plates lose coherency as the plates grow The edges of the plates:incoherent or semicoherent (CAl.●Cu) (001) 450 (100! (010) (001)Coherent or semicoherent -404A 404A 404A a-matrix 404A (100)}not coherent (010)J K.Chen 13
K. Chen Continuous Precipitation 13 Transition phases – θ’ θ’: Tetragonal unit cell with an approximate composition CuAl2 (001) planes identical with {001} α (100) and (010) planes have diff. crystal structure to the matrix large misfit in the [001] direction Forms as plates on {001}α with the same orientation relationship as θ’’ Fully coherent broad faces of the plates lose coherency as the plates grow The edges of the plates: incoherent or semicoherent
Continuous Precipitation 上游充通大兽 SHANGHAI JIAO TONG UNIVERSITY Transition phases -0' d~1μm Misfit dislocations in the broad faces of the precipitates 05 X18000 K.Chen 14
K. Chen Continuous Precipitation 14 Transition phases – θ’ X 18000 d ~ 1μm Misfit dislocations in the broad faces of the precipitates
Continuous Precipitation 上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Equilibrium phase -0 0:complex body-centered tetragonal with an approximate composition CuAl2 No plane of good matching with the matrix and only incoherent,or at best complex semicoherent interfaces (cAl.●Cu) -404A 404A Incoherent a-matrix 67A —607A K.Chen 15
K. Chen Continuous Precipitation 15 Equilibrium phase – θ θ: complex body-centered tetragonal with an approximate composition CuAl2 No plane of good matching with the matrix and only incoherent, or at best complex semicoherent interfaces