Papers by Author: Ron O. Scattergood

Abstract: This paper describes the stabilization of nanocrystalline grain sizes in Pd and Fe by the addition of Zr solute atoms. The grain size as a function of annealing temperature was measured by both x-ray diffraction (XRD) line broadening analysis and microscopy methods. The latter methods showed that the XRD grain size measurements for the samples annealed at the higher temperatures were not valid. It appears that thermodynamic stabilization may still be operative in the Fe-4at.% Zr alloy but not in the Pd-19at.% Zr alloy from the experimental results and calculations of the enthalpy of segregation.

Abstract: Shear punch test (SPT) has been used to study the mechanical properties of Cu, Cu–10 wt.% Zn, Cu–20 wt.% Zn and Cu–30 wt.% Zn after ball milling with an average grain size in the range of 33-12nm. The strain rate sensitivity (SRS) and physical activation volume have been determined. The magnitude observed for these characteristic deformation parameters is very different from their course-grained (cg) counterpart. This suggests that the thermally activated process in nanocrystalline (nc) metal/alloys is different from the conventional forest dislocation cutting mechanism. The stacking fault energy (SFE) of Cu-Zn alloys decreased with the adding of Zn, and deformation twins are anticipated to introduce into the nc Cu-Zn alloys during process of ball milling. Dislocations could accumulate along the TBs and carry the plastic strain, so the ductility of nc Cu-Zn alloys could be improved.

Abstract: This paper reviews a method, “in situ consolidation ball milling” that provides artifactfree bulk nanocrystalline samples for several ductile metals such as Zn, Al and Al alloys, and Cu and Cu alloys. The preparation method is described in this paper and examples of the mechanical behavior of nanocrystalline materials made by this technique are given. It is found that in such artifact-free metals, combinations of both high strength and good ductility are possible.

Abstract: Effect of annealing temperature is investigated on texture and creep anisotropy in a thinwalled tubing of titanium alloy. Creep anisotropy is studied under equibiaxial loading using internally pressurized tubing superimposed with axial load while monitoring in-situ the time variations of both hoop and axial strains. Relatively weak hoop direction in the cold-worked material became stronger following complete recrystallization. The analyses of the data reveal that the anisotropy parameter, P which is the contractile strain ratio for testing along hoop direction increases from around 0.6 for the cold-worked material to around 1.5 following complete recrystallization. Results indicate that planar isotropy should occur following annealing at around 800K. Work on the effects of annealing on the textures and deformation microstructures is in progress. We summarize here results from some of our earlier work on a different lot of Ti3Al2.5V tubing in the recrystallized states where the ODFs were used in conjunction with crystal slip models to predict creep anisotropy.