Microstructure of Zr Alloy Containing Nb or Cu Element

The effect of Nb and Cu on the microstructure of Zr alloys was investigated by TEM and SEM. Results show that when a trace amount of Fe element is presented, the precipitation of Nb and Fe, whose amount is below the equilibrium solid solution limitation in alpha-Zr, are promoted by adding the appropriate amount of Cu element, leading to the lower content of Nb in alpha-Zr alloys. However, the precipitation of Nb-enriched phase is inhibited by the further addition of Cu amount since the Fe element is consumed by the enrichment of Zr2Cu phase. Meanwhile, Zr2Cu phase in Zr-1.0Cu alloy is significantly refined and uniformly distributed after the addition of Nb element. In the presence of beta-Zr secondary phase stabilized by a large amount of Nb element, a small amount of Cu element is enriched within the beta-Zr phase rather than being precipitated as Zr2Cu.