A mechanical properties microprobe is an exciting concept. A system with the ability to evaluate the mechanical response of a sample with submicron spacial resolution would have an extremely wide range of applications. Recent developments in hardware and understanding have placed this goal within our grasp.

In 1971, J.J.Gilman wrote the following in his article, “Hardness—A Strength Microprobe”:

“Hardness measurements are at once among the most maligned and the most magnificent of physical measurements. Maligned because they are often misinterpreted by the uninitiated, and magnificent because they are so efficient in generating information for the skilled practitioner. They can quickly yield quantitative information about the elastic, anelastic, plastic, viscous, and fracture properties of a great variety of both isotropic and anisotropic solids. The tools that are used are simple and the sample sizes that are needed are typically small, sometimes submicroscopic. This makes it unnecessary to have large specimens in order to measure strength properties and makes it possible to measure the properties of various microscopic particles within the matrix phase of a polyphase metal, mineral, or ceramic material. This is why hardness may be considered to be a strength microprobe.”

These statements are worth repeating for two reasons. First, they point out the largely untapped potential for microin-dentation tests to improve our understanding of the mechanical properties of materials. Second, it is the first mention of hardness tests in the context of a strength microprobe. In this article the more general term of microindentation tests will be used, since hardness is only one of many properties that can be measured with such tests. In addition, the term mechanical properties microprobe (MPM) will be used rather than strength microprobe-again, to note the wide variety of properties that can be measured.

The competitive forces that have dominated the aluminum industry over the last decade are similar to those in many other industries. New international competitors, driven primarily by their ability to compete with long-standing U.S. producers on the basis of cost and quality, have made significant inroads into virtually all aluminum markets.

As more emerging nations, driven by the need to create jobs and hard currency rather than profits, entered the primary metal business and exported their output, ingot prices fell. Eventually, ingot became a commodity traded in the international marketplace, with metal prices no longer related to production costs.

While these structural changes in the worldwide aluminum industry are of great concern (particularly in the United States), by no means do they signal the light metal's demise in the materials marketplace. What they have done, however, is to provide the impetus for the development and pursuit of economic and technical strategies designed to ensure long-term, profitable growth.

By the beginning of the 21st century, most monolithic metals will be firmly entrenched as commodities. This will solidify emerging nations as key producers, based upon their access to raw materials, less costly labor and energy resources, and subsidized capital. The ability of companies like Alcoa to compete in this commodity marketplace will be based upon their ability to reduce manufacturing costs and provide technically-based product differentiation, primarily via quality control, through new and improved processing technologies.

The application of Inertial Confinement Fusion to power production requires the development of a high-yield fusion capsule. Theoretical design calculations suggest that a single shell capsule with a uniformly distributed deuterium-tritium (DT) fuel layer on the inside surface could give the desired high-gain performance when directly driven with 0.35 μm laser light. This design requires operation at cryogenic temperatures necessary to condense DT (20-30 K) and a means of levitating the fuel layer inside the capsule. On e recently suggested method for making this capsule is to use a rigid foam matrix to support the condensed DT in a spherical shell configuration. For such a capsule to be successfully fielded, a number of critical materials problems must be solved.

The modeling of solidification processes is a broad field covering many different types of activities. On one level, technical aspects of casting processes are investigated by computer simulations. The modeling is then a tool for the designer and the calculations may even be integrated with a CAD/CAM system. A more fundamental level may consider how the microstructure develops during solidification and how it can be controlled. This article gives a brief historical survey of the modeling of solidification processes.

A well-known rule of thumb, often given in textbooks, states that the solidification time for a simple casting is proportional to its squared volume-to-area ratio. This rule is named after Chovrinov, who verified it experimentally in 1940. The mathematical treatment of solidification, however, has a much older tradition started more than 100 year s earlier in 1831 when Lamé and Clapeyron analyzed the growth of a solid crust generated by cooling a liquid. Their analysis showed that the thickness of the solid is proportional to the square root of time, which is also the essence of Chovrinov's rule. Their basic idea was that the solidification rate was controlled by the removal of latent heat. That idea may seem quite obvious to us, but a necessary pre-equisite for it is the concept of heat as quantifiable and transportable. Actually, Fourier had made his mathematical analysis of heat propagation only 20 years earlier and had won the prize of the French Academy of Sciences in 1811 for his contribution.

Basic and applied materials research at Argonne National Laboratory (ANL) is conducted by the Materials Science Division (MSD) and the Materials and Components Technology Division (MCT). Of the $30 million annual budget, $23 million comes from the U.S. Department of Energy (DOE) that funds Basic Energy Sciences (BES)-Materials Sciences, Reactor Development, Fusion Energy, Fossil Energy, and Conservation Technology. Another $5 million of the $30 million budget comes from the Nuclear Regulatory Commission and the remaining $2 million is from the Department of Defense.

Representative projects in fission energy include fuel element behavior in the Advanced Breeder Reactor, fuel development for the Integral Fast Reactor, and supporting research in aqueous corrosion and in phase stability.

Materials research for fusion environments includes containment materials, liquid metal compatibility, vanadium alloy development, defect production processes, radiation-induced segregation, sputtering of self-replenishing low atomic number coatings, and ultrahigh field superconductors.

The Materials Research Center at Northwestern University is an interdisciplinary center that supports theoretical and applied research on experimental advanced materials. Conceived during the post-Sputnik era, it is now in its 26th year.

The Center, housed in the university's Technological Institute, was one of the first three centers funded at selected universities by the federal government in 1960. The federal government, through the National Science Foundation, now supplies $2.4 million annually toward the Center's budget, and Northwestern University supplements this amount. Approximately one third of the money is used for a central pool of essential equipment, and the other two thirds is granted to professors for direct support of their research. Large amounts of time on supercomputers are also awarded to the Materials Research Center from the National Science Foundation and other sources.

The Center's role enables it to provide partial support for Northwestern University faculty working at the frontiers of materials research and to purchase expensive, sophisticated equipment. All members of the Center are Northwestern University investigators in the departments of materials science and engineering, chemical engineering, electrical engineering, chemistry, or physics. The Materials Research Center is a major agent in fostering cross-departmental research efforts, thereby assuring that materials research at Northwestern University includes carefully chosen groups of faculty in physics, chemistry, and various engineering departments.