Volume 17, Issue 4 (July 1989)
Effect of Strain Rate and Temperature on the Mechanical Anisotropy of Recrystallized Zircaloy TREX (Tube Reduced Extrusion)
Tube Reduced Extrusion (TREX) is an intermediate product in the production of Zircaloy canning tubes for nuclear reactors. This paper studies the mechanical anisotropy, which has a direct relation to the formability of recrystallized Zircaloy-2 TREX. The yield stresses, as well as the anisotropy parameters (R and P) in the modified Hills equation, are evaluated using impression testing as a function of test temperatures and strain rates. The impression test offers a rather direct way for evaluating R and P through the uniaxial yield stresses along the three orthogonal directions. The anisotropy of the yield stress is evident at low test temperatures and decreases at high temperatures. The anisotropy parameter R is insensitive to test temperature (room temperature to 623 K) and strain rate (10−2 to 10−3s−1) and has a value close to unity. The P parameter decreases with increasing test temperature, approaching unity at 623 K.
There is a general trend for the anisotropy parameters to approach unity (the isotropic case) with increasing test temperature. This may be due to the activation of secondary slip systems. The linear relationship between compression and impression stresses, established at different test temperatures, is insensitive to the test temperatures within our range; it is in good agreement with the literature.