Effect of strain rate on the cyclic hardening of Zircaloy-4 in the dynamic strain aging temperature range

MG MOSCATO; M AVALOS; I ALVAREZ; C PETERSEN; A ARMAS

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

Elsevier

Año: 1997 vol. 234 p. 1 - 1

0921-5093

Low cycle fatigue (LCF) tests were conducted in Zircaloy-4 with a total strain range of f 0.5% in the temperature range 573-873 K where dynamic strain aging (DSA) manifestations in uniaxial tensile tests were reported. A time dependent linear cyclic hardening stage is the principal feature observed in this alloy. The cyclic hardening rate exhibits a peak in this temperature range. In order to evaluate the strain rate effects on the cyclic hardening, tests at strain rates 2 x 10-3 s-1 and 2 x 10-4 s-1 were performed. The location of the cyclic hardening rate peak depends on the strain rate suggesting the operation of a thermally activated mechanism. Transmission electron microscopy (TEM) observations show that the linear hardening stage is characterized by a two-dimensional wall structure that evolves from the activation of two slip systems. DSA takes place during strain-controlled fatigue deformation at the same temperature range of that occurring during tensile deformation.