Abstract
The effects of irradiation on precipitation in Al-4 wt.-%Cu alloys have been studied in situ in the highvoltage electron microscope at 463 K. The results show that &03B8;′ precipitates are quickly formed and coarsen rapidly. It appears that transformation of the coherent GP and &03B8;″ phases to the semicoherent &03B8;′ phase is made easier by the point defects produced by irradiation. Thus the irradiation forces a change in the metastable phase diagram. The &03B8;′ precipitates formed by localized electron irradiation coarsen at the expense of GP zones remaining outside the irradiated volume. Measurements of precipitate distribution show that up to ten times as much copper is contained in the precipitates as in the unirradiated matrix. The irradiated volume is therefore acting as a copper sink and the mechanism for this is discussed.
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