Cu-Ni-Be-Al合金の時効性について

Abstract

For the purpose of obtaining high-strength copper alloys having high corrosion resistance, the aging characteristics and the spring property of Cu-30%Ni containing 0.47 wt%Be and 0.6∼3.0 wt%Al have mainly been investigated by means of the hardness test, X-ray diffraction, optical and electron microscopy (replica method), and the spring test.The results obtained were as follows:(1) These alloys showed a maximum hardness value at 500°∼600°C when aged at 300°∼800°C for 1 hr after water quenching from 1050°C, and maximum value in hardness at 600°C increases with the amount of added aluminum.(2) It is concluded that age hardening occurred by heating at 600°C after water quenching from 1050°C is due to the precipitation of NiBe (β) and Ni3Al, and that the hardening at an earlier stage of aging is contributed by the precipitation of non-equilibrium phase (β′) but the hardening at later stage is due to the precipitation of Ni3Al.(3) Moreover, it seems that added aluminum suppresses the grain-boundary reaction developed by the precipitation of NiBe and consequently restrains the over-aging of these alloys.(4) The alloy containing about 2.4%Al showed an excellent spring property having a maximum value of about 125 kg/mm2 in Kb, when it was cold rolled by 50% after water quenched from 1050°C and aged at 400°∼500°C for 1 hr.