Experimental data show that in Al-4. 8Zn-1. 2Mg alloys precipitation at 160C is strongly influenced by preaging at room temperature (R. T. ) and by intermediate heat treatment between R. T. and final aging. It is also shown that, although the reversion of Guinier-Preston zones formed at R. T. is followed by their dissolution at higher temperatures, the remaining high Zn and high Mg clusters act as nucleation sites for eta prime phase particles. The dispersion of these nucleation sites strongly depends on the temperature and duration of the intermediate heat treatments. This explains why basically different precipitate structures can be produced by the same final heat treatment by changing the duration and temperature of an intermediate heat treatment.
|Number of pages||7|
|Publication status||Published - Jan 1 1977|
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