Cyril Stanley Smith

Measurement of Internal Boundaries in Three-Dimensional Structures By Random Sectioning

It is shown, from a study of geometric probabilities, that the average number of intercepts per unit length of a random line drawn through a three-dimensional structure is exactly half the true ratio of surface to volume. Since the surfaces can be internal or external, the area of grain boundary or of the interface between any two constituents in a microstructure can be measured. Other metric relations are tabulated that may be of use in studies of the microstructure of polycrystalline, cellular, or particulate matter generally.

The formation of low-energy interfaces during grain growth in alpha and alpha-beta brasses

Abstract Measurements have been made of the relative areas of various types of interface observable in the microstructure of alpha-beta brasses. In alpha brass the ratio of twin-boundary area to that of grain boundary increases with grain size in accordance with the Fisher-Fullman concept of nucleation at grain corners. In alpha-beta brasses, interfaces across which the two phases are related in orientation are common and their fraction increases as the grain size of the duplex mixture increases, but this is a result of selective growth and not nucleation. These interfaces appear on microsections as straight lines similar in appearance to twins in the alpha phase, but they do not correspond to any particular orientation of the boundary plane with respect to the grains. They do, however, include the single close-packed direction common to both phases.

Further notes on the shape of metal grains: Space-filling polyhedra with unlimited sharing of corners and faces

Abstract A statement in an earlier paper that there is a topological limit to the sharing of corners in a network of three-dimensional cells analogous to metal grains is shown to be wrong. New space-filling irregular polyhedra sharing faces with as many as 20 neighbors are sketched. No plane-faced space-filling polyhedron can exist that meets the requirements of surface-tension equilibrium at interfaces and junctions. A relation is derived for the sum of angles at each vertex in a three-dimensional space-filling array of plane-faced polyhedra.

Microsampling and Microanalysis of Metals

In studies of composition gradients in diffusion samples, or for identifying inclusions, it is often desired to obtain analytical samples from minute and exactly located positions in experimental material. This paper deals with the design and use of a microshaper using a diamond tool to take linear cuts separated by as little as 0.02 mm. A hand‐driven drill can be used for sampling circular areas of diameter greater than 0.1 mm. The chips, which may weigh as little as 0.1 microgram, are picked up on an electrified quartz fiber and centrifuged into a capillary which is evacuated and sealed for annealing. A precision x‐ray diffraction photograph is then obtained from the annealed chip, and the calculated lattice parameter used as an index of composition. Two examples of the use of the technique are given.

Undercooling of minor liquid phases in binary alloys

The tin in an aluminum-tin alloy with 10 pct tin solidifies over a temperature range as high as 100°C. The tin is partly distributed in isolated droplets and the amount of undercooling depends on the chance presence of nuclei effective at various temperatures in drops of varying sizes. Heat treatment affects the size distribution and modifies the cooling curve. Similar behavior is to be expected in any alloy where the liquid is physically discontinuous and where solidification is not nucleated by a previously solidified constituent. It is probably the cause of some spurious arrests that have been observed in cooling curves of simple alloys.

Alloys of copper and iron

Studies were made of the mechanical and other properties of alloys over the entire composition range from pure copper to pure iron. Though the two-phase alloys have poor corrosion resistance unless protected, the composition in the vicinity of 65 pct Cu possesses an excellent combination of strength and electrical conductivity in the form of cold drawn wire. The alloys about 5 to 10 pct Cu have the highest strengths and are the most susceptible to improvement by age hardening treatment.