Ralph R. Sawtell

Mechanical properties and microstructures of Al-Mg-Sc alloys

The mechanical properties of Al-(Mg)-0.5Sc alloys have been investigated. Room-temperature tensile and toughness properties were found to reflect a superposition of the properties of Al-Mg and Al-0.5Sc alloys and are quite competitive with high-performance Al alloys. A combination of substructure refinement by Mg and stabilization by Al3Sc precipitates produces exceptional superplasticity as exemplified by superplastic forming (SPF) elongations in excess of 1000 pct at a strain rate of 0.01 s-1. Overall, these alloys demonstrate an extremely attractive combination of strength, toughness, density, and SPF fabricability.

ALUMINUM COMPOSITE MATERIALS FOR MULTICHIP MODULES

In the intensive materials development activities for electronic packaging and thermal management applications, the subclass of materials in which SiC particles reinforce aluminum alloy matrices has emerged as one with an especially attractive combination of physical properties, manufacturing flexibility, and cost. One benefit of these materials is the ability to tailor the physical properties through the selection of both reinforcement and alloy variables to match the thermal expansion coefficient of other electronic materials. In addition, the manufacturing flexibility of the various processes allows for shape complexity as well as selective reinforcement placement in the component to optimize system producibility. Finally, because raw materials are inherently inexpensive and low-cost production routes have been identified, aluminum composites may offer a range of cost-effective solutions to emerging problems in electronic packaging and thermal-management applications.

Functional Gradient Products Enabled by Planar Solidification Technologies

A new class of materials with engineered compositional gradients through the thickness is introduced. Ingots with different types of composition gradients through the thickness were fabricated into plate. The composition and mechanical properties of these “Functional Gradient” plate products (metallic composites) are described, and the energy absorption performance of different architectures of functional gradient products is discussed in terms of dimensionless parameters. It is concluded that ab-initio simulations of architecture and performance are needed for the development, optimization and use of functional gradient products.