Determination of complete plane-stress yield loci of Zircaloy Tubing

The elastic and plastic anisotropy of commercially fabricated Zircaloy-4 cladding tubes has been determined for all four quadrants of the yield locus. The plane-stress yield locus has shown a significant asymmetry with regard to stresses created by internal or external pressurization, respectively. Knoop hardness tests are not suited for a description of the yield behavior of Zircaloy tubes. The anisotropy of the elastic properties has been evaluated as a function of the biaxial stress state. A proposed calculation model based on an extension of the general Hooke's law is suited to predict the elastic properties of textured Zircaloy tubes for biaxial stresses at room temperature, showing that the compliance constants determined for pure zirconium single crystals are also applicable for Zircaloy. The known temperature dependence of the compliance constants described less satisfactorily the elastic data measured at 400°C.