ABSTRACT
Aluminum Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694 15.4 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697
The atom probe field ion microscope (APFIM) was originally developed as a tool for surface science by Mu¨ller and his coworkers in 1968 [1]; however, from the emerging stage of the technique, metallurgists realized that its use could solve many critical problems on the microstructures of metallic materials. By the 1980s, several groups started employing the atom probe technique for microstructural characterizations of metallic materials. It has also been applied to a wide variety of materials such as semiconductors and oxide superconductors. However, due to the poor electrical conductivity, the difficulty of specimen preparation, and the uniform microstructural features in these materials, the atom probe technique has not made much contribution to characterizations of nonmetallic materials. However, it has been successfully demonstrated that the atom probe is extremely useful for characterizing metallic nanostructures that are composed of nanoscale precipitates dispersed in a matrix phase. The atom probe technique gives unique information on metallic nanostructures that is unattainable with other analytical microscopy techniques such as transmission electron microscopy (TEM); it can detect light elements such as carbon, boron, oxygen, and nitrogen in a subnanoscale resolution. The atom probe has a very high spatial
resolution in compositional analysis, and it can even measure the chemical composition of nanoscale particles embedded in a matrix phase. It can also detect small solute clusters that are not detectable by a high resolution electron microscope (HREM). Because of these unique features, the atom probe technique has been widely used for nanoscale analysis of metallic microstructures. In particular, it has been demonstrated that this technique is useful in characterizing the microstructural evolution in the early precipitation stage of age-hardenable aluminum alloys, in which clustering of solute atoms plays a critical role in the microstructural evolution. This paper intends to give an overview in the application of the atom probe technique in characterizing the microstructures of various aluminum alloys of commercial importance.
