Abstract
The aging characteristics of Cu-30%Ni-Be-Si alloys containing both Be(0.4∼0.5%) and Si(0.3∼0.6%) were investigated by means of hardness tests, optical microscopic observations and micro-beam X-ray diffraction. The results obtained were as follows:
(1) These alloys showed superior mechanical properties (hardness and Kb value) than Cu-30%Ni-Be alloy, and the maximum hardness values of these alloys increased with the addition of silicon.
(2) It is shown that the age-hardening of these alloys is due to the precipitation of NiBe (γ phase) at an earlier stage of aging and due to the precipitation of Ni3Si (β1 phase) at a later stage of aging.
(3) By addition of silicon, G.P.zone was stabilized for a long period, the formation of non-equilibrium phase γ′ (or γ″) was retarded and the grain boundary reaction was supressed.
(4) The qualitative relationship was observed between the width of the nodule (the discontinuous precipitates) at grain boundaries and the orientation difference angle of the neighbouring crystals. The width of the nodule became wider with the increasing orientation difference angle of the neighbouring crystals.
