Grain refinement is one of the most effective strengthening mechanisms, improving mechanical properties without loss in ductility. It is well known, however, that proper prediction of mechanical properties of fine grained materials is much more complicated because of different deformation and strengthening mechanisms operating in these materials. When the strong grain refinement (below 1 μm) is achieved, some deviations compared to conventional materials have been reported, i.e. change in Hall–Petch slope, different deformation mechanism, enhanced strain rate sensitivity, lack of work hardening or different fracture mechanisms. Unfortunately, these phenomena and their physical basis are still poorly understood and most of the well known constitutive laws (i.e. Hall–Petch relationship) are no longer effective for a description of the deformation processes of such materials. This paper discusses selected problems relating to mechanical behavior of submicron/nano grain size materials.

Oxide dispersion-strengthened (ODS) iron aluminide alloys based on Fe3Al have been formed by reaction synthesis from elemental powders followed by hot extrusion. The resulting alloys have approximately 2.5% by volume Al2O3 particles dispersed throughout the material. A proper combination of extrusion temperature, extrusion ratio, and post-consolidation heat treatment results in a secondary recrystallized microstructure with grain sizes greater than 25 mm. ODS material with 5% Cr addition exhibits approximately one order of magnitude increase in time to failure at 650°C compared to a similar alloy without the oxide dispersion. The activation energy for creep in the 5% Cr ODS material is of the order of 220 kJ⁄mol and the power law creep exponent is approximately 9.8. Transmission electron microscopy examination of the substructure of deformed samples indicates some formation of low angle dislocation boundaries, however, most of the dislocations are pinned at particles. The TEM observations and the value of the creep exponent are indicative of dislocation breakaway from particles as the rate controlling deformation mechanism. The TEM results indicate that particles smaller than approximately 50 nm and larger than approximately 500 nm do not contribute significantly to dislocation pinning. Addition of Nb and Mo along with Cr results in decreased minimum creep rates, however, the time to rupture is greatly reduced due to fracture at low strains initiated at large Nb particles that were not put into solution.

Constitutive equations for AA3003 and AA3102 in the conditions of as-homogenized extrusion billet and as-extruded tubing have been set forth in a tensile mode, and in a compressive mode involving longitudinal upsetting of the tube cross section. The data have been analyzed by way of the classical Zener–Hollomon approach, and strain, in the range of six, increases flow stress ∼50%, thus increasing press load projections ∼25%.

A diffusion based model has been developed to predict the structure of a galvannealed coating. The model has been expressed as a C++ program that can be used to find the optimal line speed and annealing furnace temperature. The physical constants of the model were calibrated using industrial samples and samples exposed to thermal cycles simulating the annealing process. The model can be used to find optimal coating structures and production rates. Various quality issues are discussed; in particular the variable surface roughness caused by variations in Al from the flux used in flux hot-dip coating lines.

As-annealed, 2.47 mm ETP copper wire was drawn in bye passes to 1.45 mm using carbide dies with nominal included angles of 8, 16 and 24 degrees. A single die, low speed drawing block was used, and the lubricant was fat-based and water soluble. Annealing was undertaken in a box furnace, for six minutes at temperatures ranging from 185 to 230 degrees C. Annealing response and texture evolution were assessed by way of tensile tests, microhardness measurements and x-ray diffraction. Redundant strain accumulation was projected by way of deformation zone geometry, or Delta, analysis.The as-drawn wire reveals volumes of (111) and (200) fiber texture, as well as a significant volume of essentially randomly oriented grain structure. The ratio of(111) to (200) texture decreases as die angle increases. Increases in die angle and related redundant strain promote the development of random orientation and reduce the sharpness of the (111) and (200) texture components. Increases in die angle and related redundant strain also lower the annealing temperature range and cause nonuniform recrystallization, presumably due to redundant strain and texture gradients. The as-annealed 1.45 mm wire displays a large volume of randomly oriented grain structure for all three die angles. In the case of the as-annealed wire, increases in die angle are associable with a decrease in the volume percent of (111) fiber texture, a decrease in the sharpness of the (200) fiber texture, and an increase in randomly oriented grain structure.

The use of high metal processing speeds to meet the demands for increased productivity has focused attention on the pronounced heating of tooling and workpiece which occurs under these conditions. In the present study, heating under hydrodynamic conditions in wire and strip drawing is addressed by considering a two-dimensional representation of the tool-lubricant-workpiece interface. An analytical formulation is presented for prediction of the resultant temperatures. The model considers deformation heating in the strip, lubricant viscosity to be a function of temperature and pressure, and matches the heat flux at the strip-lubricant boundary. Convection of heat in the lubricant film is considered. The model is constructed in terms of the governing non-dimensional parameters and solved by a Crank-Nicolson finite difference technique. By comparison with solutions which do not consider convection, it is found that convection only begins to play a role in the resulting temperatures when the Graetz number U(0)h(0)(2)/alpha(L)l is greater than 0.4. For the high speed drawing of aluminum with mineral oil used as a lubricant, the model predicts a monotonic increase in mean lubricant temperatures from 366 K to 404 K over a range of initial strip velocities of 20.3 m/s to 50.8 m/s. The maximum strip surface temperature is predicted to monotonically decrease from 345 K to 335 K over this range of strip velocities. The ratio (k(L) rho(L)c(pL)/k(s) rho(s)c(ps))(1/2) is shown to be important in determining the relative temperatures of lubricant and strip. Results are compared to those metal-working analyses which do not consider the role of lubricant film.

Investigations utilizing agonists for 5-HT receptor subtypes have been conducted to determine which 5-HT receptor subtype(s) subserve myoclonus in the guinea pig. Administration of a nonselective 5-HT agonist such as 5-MeODMT (5-HT1A/5-HT2 agonist) induces a dose-dependent behavior characterized by head jerking at low doses (1-2 mg/kg, SC) and full-blown myoclonus (continuous rhythmic whole-body jerking) at higher doses (2.5-5 mg/kg, SC). In contrast, the selective 5-HT1A receptor agonist 8-OH-DPAT and the selective 5-HT2 receptor agonist DOI do not induce myoclonus, and elicit only limited head jerking across an otherwise behaviorally active range of doses (1-5 mg/kg, SC). Importantly, the coadministration of both 8-OH-DPAT and DOI results in the emergence of dose-dependent myoclonic behavior. These data suggest that coactivation of 5-HT1A and 5-HT2 receptors may be required for the induction of myoclonus in the guinea pig.

The objective of our research is to develope for process manufacturing an inferential quality control system that combines theoretical and experimental knowledge of physical processes with the judgement and experience of experts in plant operations. In this paper, we propose a quality process model, and apply the model to the continuous electrical resistance annealing of copper wire. Theory is used to develop the relationship between the control variables and measurable characteristics of the process, and experimental information is used to develop the relationships that link the process characteristics to the quality characteristics specified by the customer. The approach is illustrated by the manufacturing process, the continuous annealing of copper wire.

The use of high Tc superconductors, namely YBa2Cu3O7−x, in the design of electrical componentry shows a great potential for energy savings in the transmission and generation of electrical power. Through characterization of the physical and mechanical properties of these materials, their usefulness in engineering practices can be predicted. The strain reqiured to form and propagate cracks has been considered. The role of crystallographic texture in achieving optimum mechanical and electrical properties will also be discussed.

The abrasive wear and cavitation erosion resistance of several alloys based on the intermetallic compounds Ni3Al and Fe3Al have been investigated. The erosion resistance of the nickel aluminides is relatively insensitive to alloying with iron or chromium and is comparable with or superior to that of many commercial erosion-resistant alloys; the abrasive wear resistance is found to be decreased by alloying, despite increased room temperature strength and refined grain size. Preliminary results for the iron aluminides indicate increased resistance to abrasive wear with increasing alloy content. It is suggested that the abrasive wear process causes temperature increases in the damage zone that are sufficient to cause the elevated temperature properties of the alloys to become dominant. Under these conditions, the wear resistance can be related to the tendency to disorder, either thermally or through plastic deformation.

The results of transmission electron microscopy studies on YBa2Cu3O7-x subjected to high temperature extrusion are presented. Particular emphasis is put on high temperature accommodation processes of lattice dislocations into sub-grain boundaries. It is suggested from the electron microscopy observations that stress induced climb mechanisms for dislocations are operative. Also presented is evidence of localized lattice distortions near twin boundaries due to isothermal high temperature deformation. Preliminary results on the structure of grain boundary facets and steps is described. The implications of these results for texture development in bulk ceramic superconductors is also discussed.

Plastic deformation and texture development in polycrystalline YBa2Cu3O7− δ has been studied to expedite the process development of high-critical-temperature (high-Tc) superconducting wires and tapes. It is anticipated that deformation texture will be a major processing consideration in terms of maximizing critical current density, assessing conductor-fabrication options in light of critical current density, and developing such mechanical properties as strength, toughness and thermal fatigue. The intrinsic texture development in YBa2Cu3O7− δ deformation processing should be highly beneficial, insofar as the c axes of the crystals tend to become oriented along the compression axis. This means that conducting tapes and wires formed by rolling, extrusion and drawing can develop textures with the c axis in the transverse or radial direction, thus maximizing the flow of current along the length of the conductor.