FIZIKA A 4 (1995) 3, 529-538

LATTICE CONSTANT OF Al-RICH a-PHASE IN EQUILIBRIUM WITH DIFFERENT PRECIPITATES IN Al-Zn ALLOYS

STANKO POPOVIĆ^(a,b), BISERKA GRŽETA^(b), HANS LÖFFLER^(c) and GOTTFRIED WENDROCK^(c)
(a)Physics Department, Faculty of Science, 10001 Zagreb, P.O.B. 162, Croatia
^(b)Ruđer Bošković Institute, 10001 Zagreb, P.O.B.˙1016, Croatia;
^(c)Martin-Luther Universität, D-06099 Halle (Saale), P.F.˙8, Germany

Dedicated to Professor Mladen Paić on the occasion of his 90^th birthday

Received 15 June 1995

A series of Al-rich Al-Zn alloys were studied by X-ray diffraction at room and elevated temperatures. Using the present results and those cited in literature, the following conclusion can be drawn. The lattice constant, a[a(M/P)], of the matrix, i.e. the phase a(M) in contact with various sorts of precipitates, P, depends on the initial Zn content, x, only in case of fully coherent P, i.e. GP zones. In other cases, where P's are semicoherent or incoherent a^˘_R, a^˘ or b(Zn) phases, a[a(M/P)] is independent of x, but increases with diminishing degree of coherency. The difference in the Zn content between P and a(M) determines the observed changes of the lattice constant.

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