METALLURGY OF ZIRCALOY-2. PART II. THE EFFECTS OF FABRICATION VARIABLES ON THE PREFERRED ORIENTATION AND ANISOTROPY OF STRAIN BEHAVIOR
The preferred orientation and anisotropy of strain behavior of Zircaloy- 2 were studied as functions of fabrication variables. An inverse-pole-figure technique was used for the preferred orientation determinations. Evaluation of the effects of the fabrication variables on the anisotropy of strain behavior was accomplished by a contractile strainaxial strain analysis. An analysis of strain behavior in the normal direction was developed on the basis of theory of plastic flow of anisotropic metals. A simple intuitively derivable relation was found to exist between the strainstrain analysis and the preferred orientation data. Correlations of the strain-strain data with true-stress-truestrain diagrams and mechanical properties were attempted. The preferred orientation of Zircaloy-2 produced by the Oak Ridge National Laboratory-Homogeneous Reactor Project (ORNL- HRP) metallurgy fabrication schedule (ingot breakdown at 1500 to 1900 deg F, major reduction at 1800 to 1900 deg F or 1350 to 1450 deg F, a heat treatment of 30 min at 1800 at 1550 deg F followed by a water quench or rapid air cool to below 1200 deg F, a final reduction of 25 to 40% at 1000 deg F. and a 3O-min anneal at 1400 to 1425 deg F) was weak compared to that of most of the other schedules investigated. Elimination of the beta heat treatment (1800 to 1850 deg F for 30 min) between the major reduction and final reduction steps resulted in a material with a high degree of preferred orienation and with a state of pseudoisotropy in ihe rolling plane. A unique and quite high degree of preferred orientaion was developed when the ORNL-HRP metallurgy fabrication procedure was used, but the ingot axis was in the transverse rather than the rolling direction of the finished plate permitting more contractile sirain to occur in the normal direction than in either the rolling or transverse directions. The strain-strain analyses of the materials were consistent with the conclusions reached by the preferred orientation analyses. The effects of cross rolling on the anisotropy of strain behavior of Zircaloy-2 were found to depend on the type of cross rolling (unidirectional or rotational), the temperature of cross rolling, and the stage of fabrication at which the cross rolling was done. Unidirectional cross rolling at 1000 deg F after beta heat treatment caused only a slight increase in anisotropy of strain behavior over that for straight-rolled material, but roiational cross rolling at 1000 deg F after beta heat treatment resulted in a material with a state of isotropy of strain behavior only in the rolling plane. Rotational cross rolling before beta heat treatment, for one material at 1450 deg F and for another from 1900 deg F, produced different states or degrees of anisotropy of strain behavior. Because of flow constraints which exist in sheettype tensile specimens with width-to-thickness ratios > 1.0, it is imperative that round tensile specimens be used in the contractile strain-axial strain analysis. Since the principal axes of anisotropy are generally not the major sheet directions, they must be found by the preferred orientation analysis. (auth)
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-15-007724
- OSTI ID:
- 4102432
- Report Number(s):
- ORNL-2948
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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