Transformation Superplasticity in Zircadyne 705

Abstract

The zirconium alloy Zircadyne 705 (main alloying addition: 2.5 wt.% Nb) was thermally cycled from 900 °C (100% β-phase) to 710 °C (80% α-phase and 20% β-phase), resulting in strain increments after each cycle that are linearly proportional to stress up to 2 MPa. Tensile elongations in excess of 240% were achieved without fracture. The Newtonian flow behavior and high ductility indicate that transformation superplasticity is the dominant deformation mechanism. The superplastic strain increment decreases as the cycling amplitude and period decrease, in general agreement with existing transformation superplasticity models.