Texture development and anisotropic deformation of zircaloys

Impression creep and impression fatigue, both using cylindrical indenters, are reviewed in this paper. For impression creep, analytical solutions and computer simulations for different situations are presented. Materials tested include metals and alloys, superplastic materials, weldments, glasses, ceramics and polymers. Viscosity measurements using indentation techniques and impression creep of thin films are discussed also. For impression fatigue, a steady state per cycle is shown and the power law dependence of maximum stress is presented. Underloading and overloading effects, as well as delayed retardation, are described. Other localized tests, such as nanoindentation, stress relaxation, impression recovery and the adhesion energy determined by impression testing, are briefly discussed also.

Impression creep and other localized tests

Mechanical properties of alloys consisting of two ductile phases

The present study compares the indentation and uniaxial creep behaviour of a near-γ-TiAl alloy with a duplex microstructure. Indentation creep tests were performed using a cylindrical indenter at temperatures between 750 and 1050 °C and net section stresses between 50 and 1430 MPa. A stress dependent stress exponent ranging from 3 for low net section stresses to 8 for high net section stresses was determined. The apparent activation energy of indentation creep was determined as 343±16 kJ mol −1 . The stress as well as the temperature dependence of the indentation and uniaxial creep data are in good agreement. The indentation experiments were also analysed with respect to the deformed volume in front of the indenter and the surface bulge that develops around the indenter. A simple dislocation model is proposed to rationalize volume and shape of the bulge around the indenter. The good agreement of creep parameters obtained by indentation and conventional uniaxial creep testing demonstrates that indentation creep tests are suitable to characterize creep.

Creep of a TiAl alloy: a comparison of indentation and tensile testing

Interpretation of impression creep data using a reference stress approach

Etude experimentale sur les 3 faces adjacentes de l'echantillon sous une contrainte d'impression de 25,09 MPa. Determination des courbes temps-profondeur d'impression. Determination des energies d'activation de temperature par des essais de variation de temperature (398 a 498 K). Bon accord avec les essais de fluage conventionnels

Creep anisotropy of zinc using impression tests

Hexagonal closed packed metals like zirconium are inherently anisotropic and deformation during processing leads to the development of preferred orientation or texture in the finished product. The texture is known to affect the yield properties of the finished product. Tube Reduced Extrusions (TREX’s) are an intermediate product in the production of ZIRCALOY-4* canning tubes for the nuclear industry. The use of the impression test for measuring mechanical anisotropy is demonstrated in this paper. The effect of textural variations due to changes in annealing temperature of ZIRCALOY-4 TREX on room temperature yield anisotropy has been studied. Recrystallization of the asreceived/cold-worked TREXdoes not reduce the degree of anisotropy in the TREX but influences its nature. The results are analyzed both in terms of qualitative pole-figures as well as the upper bounding Bishop-Hill plasticity model using quantitative CODF descriptions. The qualitative pole-figure analyses were found to inadequately predict the anisotropy. The upper bound plasticity model successfully predicts the yield anisotropy of TREX at room temperature.

Effect of annealing temperature on yield anisotropy of ZIRCALOY-4 TREX

A personal computer based system to evaluate J-integral by a single specimen unloading compliance method—part II: Results on A533B class I steel and corona-5

The influence of the material parameters, strain hardening, and strain-rate hardening on the plastic instability of textured zinc sheets tested in uniaxial tension was investigated. The experimental instability strains are observed to be in accord with those evaluated from the analytical expressions involving the material parameters. The crystallite orientation distribution function obtained from the pole figure data is used in conjunction with a plasticity model to predict the anisotropy parameters (R and P) and subsequently the width strains in longitudinal and transverse zinc sheets. While the experimental R and P values matched well with those predicted for basal slip, the predicted width strains beyond uniform deformation are observed to be higher than the experimental values.

P. S. Godavarti

Papers

Creep anisotropy of zinc using impression tests

Effect of annealing temperature on yield anisotropy of ZIRCALOY-4 TREX

A personal computer based system to evaluate J-integral by a single specimen unloading compliance method—part II: Results on A533B class I steel and corona-5

Plastic Instability and Mechanical Anisotropy of Textured Zinc