Effect of strain rate on the tensile properties of unirradiated and irradiated V-4Cr-4Ti

Tensile tests were carried out on an annealed, unirradiated V-4Cr-4Ti alloy from RT to 850 degreesC at strain rates ranging from 10(-1) to 10(-5) s(-1). Below 300 degreesC, where interstitial solutes are relatively immobile, deformation is homogeneous, and the strain rate sensitivity (SRS) of the yield and how stress is positive. Between 300 degreesC and 700 degreesC, the formation of solute atmospheres at locked dislocations results in dynamic strain-aging (DSA), deformation becomes heterogeneous, and the SRS of the flow stress is negative; in this regime the lower yield stress is independent of strain rate. Above 700 degreesC, substitutional solutes are also mobile, DSA declines, and the material enters a power law creep regime in which the SRS becomes positive again. Following neutron irradiation to 0.5 dpa at temperatures less than or equal to 400 degreesC, severe flow localization occurs due to the high number density of [110] and [111] loops. However, above 400 degreesC, strain hardening capacity returns but without the Luders extension. At 500 degreesC, after several percent plastic deformation, DSA occurs as interstitial solutes are released from the defect structure. (C) 2000 Elsevier Science B.V. All rights reserved.