| Abstract: | A pure as well as the analogous technical alloy were directly quenched from Tq = 400 °C or 490 °C to Ta, preaged at Ta (ranging between 50 °C and 160 °C) various times (ta), and subsequently postaged at R.T. up to tpost = 42 d. — Ageing the samples below the upper limit temperature of the homogeneous formation of G.P. zones (Thn) no essential difference in the course of the HV-number attained after one- as well as two-step ageing in dependence on the addition of impurity atoms and Tq could be found. — Contrary to this behaviour after pre-ageing at Ta > Thn and postageing at R.T. a variation of both Tq and the content of impurity atoms shows a considerable effect. The reason is the difference in the density of nucleation sites for heterogeneous formation of precipitates of the η′- and/or η-phase in dependence of Tq and impurity content. |
