Structural Properties and Stability of Metastable Phases in the Zr-Nb System: Part I. Systematics of Quenching-and-Aging Experiments

摘要

An experimental study is presented of the effect of an isothermal treatment ("aging") at 773 K upon the structural properties of three metastable phases formed by quenching Zr-Nb alloys from 1273 K, viz., hcp (#alpha#), bcc (#beta#), and #OMEGA#. Using neutron-diffraction (ND) measurements and Rietveld analysis, the lattice parameters (LPs) and the constitution of Zr-Nb alloys with up to 18 at. pct Nb are determined. By combining these data with the LP vs at. pct Nb relations previously determined by us on quenched alloys, an analysis is performed of the composition changes and phase reactions occuring upon aging. The present results open up the possibility of using quenching-and-aging experiments to gain insight into the #alpha# + #beta# metastable equilibrium in the Zr-rich side of the Zr-Nb system.