There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Mechanical Alloying And Milling

Elements Of X Ray Diffraction

Mathematical Methods of Physics.

Smithells Metals Reference Book

The relationship between Vickers hardness, yield stress and tensile strength was analyzed by combining data from two independent studies involving 7010 alloy plate and a rectilinear forging. The hardness–yield stress data from the two studies overlapped, suggesting a possible fundamental relationship. Constraint factors calculated by using contact mechanics models were evaluated and the one found by Shaw and DeSalvo was found to agree with the slope for the hardness–yield stress data. The y-intercept of the hardness–yield stress relationship was explained by the work hardening taking place during Vickers testing. The equation found to fit the hardness–yield stress data for 7010 plate and forgings also provided a very respectable fit to a third independent study. Moreover, an empirical equation was developed to express the hardness–tensile strength relationship.

/pdf/hardness-strength-relationships-in-the-aluminum-alloy-7010-2nbtwki92v.pdf

Hardness–strength relationships in the aluminum alloy 7010

The traditional contour method maps a single component of residual stress by cutting a body carefully in two and measuring the contour of the cut surface. The cut also exposes previously inaccessible regions of the body to residual stress measurement using a variety of other techniques, but the stresses have been changed by the relaxation after cutting. In this paper, it is shown that superposition of stresses measured post-cutting with results from the contour method analysis can determine the original (pre-cut) residual stresses. The general superposition theory using Bueckner’s principle is developed and limitations are discussed. The procedure is experimentally demonstrated by determining the triaxial residual stress state on a cross section plane. The 2024-T351 aluminum alloy test specimen was a disk plastically indented to produce multiaxial residual stresses. After cutting the disk in half, the stresses on the cut surface of one half were determined with X-ray diffraction and with hole drilling on the other half. To determine the original residual stresses, the measured surface stresses were superimposed with the change stress calculated by the contour method. Within uncertainty, the results agreed with neutron diffraction measurements taken on an uncut disk.

/pdf/measuring-inaccessible-residual-stresses-using-multiple-20xyrp9ott.pdf

Jeremy S. Robinson

Papers

Hardness–strength relationships in the aluminum alloy 7010

Measuring Inaccessible Residual Stresses Using Multiple Methods and Superposition

Quench sensitivity and tensile property inhomogeneity in 7010 forgings

The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075

Residual stress reduction in 7175-T73, 6061-T6 and 2017A-T4 aluminium alloys using quench factor analysis