Abstract
The mode of the diffusion zone formed by reaction diffusion by annealing at the vicinity of the α\
ightleftharpoonsβ phase transformation temperature and some properties of the intermediate phases were investigated for Zr-Cu and Zr-Nb alloy-Cu couples.
ZrCu4 and ZrCu3 were predominantly formed in the intermetallic compounds zone by isothermal annealing and the thickness of each intermediate phase varied with annealing time according to the parabolic rate law. The martensitic zirconium solid solution zone containing about 2% of Cu was formed by ten times as thick as the intermetallic compounds zone above the eutectoid temperature of the Zr-Cu system. In the α-Zr temperature range, the zirconium solid solution zone was scarcely formed, and no copper solid solution zone was observed under the present experimental conditions.
The shifts of the Kirkendall marker to the Cu side showed that Cu atoms diffuse as faster than Zr atoms.
In the diffusion couple of Zr-Nb alloy with Cu, the reaction temperature at which a similar degree of the diffusion zone was formed was about 100°C lower than that for the pure Zr-Cu couple. Micro-hardness (V.H.N.) of the intermediate phases zone were about 750 to 830 and the values are higher than the synthetic compound.
In the pickling acid solution of HNO3 or a mixture of HNO3 and H2SO4, ZrCu4 and ZrCu3 dissolve quickly, but ZrCu, Zr2Cu and Zr are almost insoluble. All of the intermetallic compounds in the Zr-Cu system dissolve quickly in the acid mixture of HF.
