The effect of heat treatment on the tensile strength and hardness of a quenched ternary zirconium-base alloy (Zr-0.5 wt.% Nb-1 wt.% Cr)

Abstract

The response of a ternary zirconium-base alloy, Zr-0.5 wt.% Nb-1 wt.% Cr, to hardening by thermal treatment has been investigated. A marked increase in the strength of the alloy was observed when it transformed to a martensitic structure after rapid cooling from the high temperature phase field, α + β or β. The structure of the as-quenched martensite was found to be hexagonal close-packed and it was supersaturated with respect to the solute elements (Cr and Nb). Tempering of this structure in the temperature range 400°–700°C lowered the hardness, an appreciable decrease being observed on tempering above 500°C. Factors responsible for the high strength of the as-quenched martensite are suggested.