抄録
Precipitation process of Cu-30%Ni-1∼3%Al alloys during aging at 500°C or 600°C after water quenching from 1050°C, and characteristics of the nodule formed by grain boundary reaction in these alloys were investigated by means of optical and electron microscopy, hardness measurement and X-ray diffraction.
The results obtained were as follows:
(1) At 500°C, hardening occurred in two stages and the maximum values in hardness were not still obtained after aging for 2×104 min. At 600°C, the hardness increased monotonously and reached their maximum after 1000 min aging.
(2) The lines of θ phase and the side bands were observed from the early stage of aging on X-ray diffraction patterns. The structure of the θ phase was ordered fcc.
(3) In the transmission electron micrographs, the modurated structure were observed at the early stage of aging.
(4) The mode of precipitation in the alloys was of the discontinuous type: α super-saturated solid solution→modurated structure→equilibrium α phase+equilibrium θ phase with composition of a extent from (Ni0.67Cu0.33)3Al to (Ni0.85Cu0.15)3Al.
(5) Fine structure inside the nodule grew and changed gradually during aging, and a granular θ phase was observed at the latter stage of aging.
(6) The hardness inside the nodule changed in nearly the same way as that inside the grain.
