38.1 Introduction

Metallic materials that are outside the mainstream of conventional metals and alloys, with respect to composition, structure and/or processing, are discussed in this chapter. The materials considered are as follows:

1. structural intermetallic compounds;

2. metallic foams;

3. metallic glasses;

4. micro- and nanoscale materials;

These materials are in different stages of development. Metallic glasses are technologically mature materials, with long-established commercial applications, although there continue to be exciting developments in the area of bulk metallic glasses. Metallic foams are the subject of a quite intense research effort at the time of writing, but have already found commercial success in a number of markets. Structural intermetallic compounds have been the subject of major world-wide research activities dating back over many years. However, significant barriers remain to the widespread commercial implementation of these materials. Metallic nanomaterials feature in much contemporary research and the details of these are still very much subject to change. However, work on the fundamentals of these materials has reached a point where this can usefully be summarised.

38.2 Cross References

The following contain information that is relevant to the contents of this Chapter:

1. crystallographic data on intermetallics Chapter 6;

2. shape memory alloys Chapter 15;

3. thermoelectric materials Chapter 16;

4. superconducting materials Chapter 19;

5. magnetic materials Chapter 20;

6. metal matrix composites Chapter 37.

38.3 Structural Intermetallic Compounds

Intermetallic compounds are employed commonly to strengthen conventional alloys. Two examples are:

• Age-hardenable aluminium alloys, strengthened by a variety of intermetallic phases, as discussed in Section 29.3.

• Nickel-base superalloys (for which an overview can be found in reference 1), with...