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The effect of solute supersaturation on the ageing process of an Al 59,5 wt% zn alloy
Author(s) -
Ciach R.,
Dutkiewicz J.,
Kroggel R.,
Löffler H.,
Wendrock G.
Publication year - 1975
Publication title -
kristall und technik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0023-4753
DOI - 10.1002/crat.19750100207
Subject(s) - spinodal decomposition , nucleation , spinodal , alloy , quenching (fluorescence) , materials science , electrical resistivity and conductivity , phase (matter) , supersaturation , thermodynamics , crystallography , chemical physics , metallurgy , chemistry , fluorescence , optics , physics , organic chemistry , electrical engineering , engineering
The effect of the solution treatment temperature on the mechanism of the decomposition at room temperature of an quenched Al 59,5 wt.‐% Zn alloy has been examined. The investigations were carried out using X‐ray techniques, optical and transmission electron microscopy and measuring the changes in the dimensions, electrical resistivity and the hardness. The sequence of the phase transformations in the alloy quenched from 370°C were as follows. The transformation begins with spinodal decomposition. After some development of the spinodal structure, which is associated with increase in wavelength, the heterogenuous nucleation and growth of the zinc‐rich particles occur within the spinodal structure. Simultaneously the discontinuous transformation was observed to grow into the spinodal structure. The decomposition of the same alloy quenched from 300°C (miscibility gap region) took place much more rapidly than when quenched from 370°C. Directly after quenching the spinodal structure was also observed using JEM‐1000, coincidental with a remarkable increase of electrical resitivity. At the same time the heterogenuous nucleation and growth of the zinc particles, on the interfaces of the α‐α′ phases was observed. The discontinuous transformation was also found within the α′ supercooled phase. The decomposition of the Al 38 at.‐% Zn alloy quenched from 300°C appeared to be divided into two stages. In the first the decomposition of the zinc‐rich α′ phase takes place and in the second one the transformation of the zinc‐poor a phase occurs. These two transformations are distinctly marked on the curves of the changes in the dimensions, electrical resistivity as well as in the intensity of the (101) reflexion of the zinc phase.