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The Coming of Materials Science Episode 4

Tham khảo tài liệu 'the coming of materials science episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 100 The Coming of Materials Science Figure 3.16. Widmanstiitten precipitation of a hexagonal close-packed phase from a face-centred cubic phase in a Cu Si alloy. Precipitation occurs on 1 1 1 planes of the matrix and a simple epitaxial crystallographic correspondence is maintained. 0 0 0 l hex II 1 1 l cub after Barrett and Massalski 1966 . transformations of this kind plates are formed in such a way that the atomic fit at the interface is the best possible and correspondingly the interface energy is minimised. This work and an enormous amount of other early research is concisely but very clearly reviewed in one of the classic books of physical metallurgy. Structure of Metals Barrett and Massalski 1966 . The underlying mechanisms are more fully examined in an excellent text mentioned earlier in this chapter Porter and Easterling 1981 while the growth of understanding of age-hardening has been very clearly presented in a historical context by Martin 1968 1998 . The historical setting of this important series of researches by Barrett and Mehl in the 1930s was analysed by Smith 1963 in the light of the general development of X-ray diffraction and single-crystal research in the 1920s and 1930s. The Barrett Mehl work largely did without the use of single crystals and X-ray diffraction and yet succeeded in obtaining many of the insights which normally required those approaches. The concept of epitaxy orientation relationships between parent and daughter phases involved in phase transformations had been familiar only to mineralogists when Barrett and Mehl began their work but by its end. the concept had become familiar to metallurgists also and it soon became a favoured theme of Precursors of Materials Science 01 investigation. Mehl s laboratory in Pittsburgh in the 1930s was America s most prolific source of research metallurgists. The kinetics of nucleation-and-growth phase transformations has proved of the greatest practical importance because it governs the process of