Correlation of microstructure and mechanical properties of Zr-Sn alloys

This paper reports on the role of tin as a solid solution strengthener and a precipitation hardener in zirconium base alloys that has been examined. Mechanical properties and microstructure of Zr-Sn binary (0.5 to 8 wt% Sn) alloys were investigated in both β-quenched and tempered conditions. The yield and ultimate tensile stresses and the percentage elongation were evaluated as a function of tin content, C, in both β-quenched and tempered Zr-Sn alloys. The 0.2% yield stress shows a linear relationship with C2/3, suggesting the operation of the Mott-Nabarro model of solid solution strengthening in which clustering of solute atoms is envisaged. The presence of tin solute clusters could also be detected in TEM microstructures of β-quenched alloys. The effect of tin content on the yield and flow behavior of zirconium has been examined at temperatures between 77 and 673 K. Results indicate that the addition of tin influenced both the thermal and athermal components of flow stress. The activation volume was found to be independent of the plastic strain, while it showed an increase with temperature and a decrease with solute content. The deformation process appeared to be controlled by two rate-controlling mechanisms: dislocations overcoming the substitutional solute clusters at temperatures below 473 K, and movement of jogged screw dislocations at higher temperatures