Solidification of metals and alloys

Source Data from J. H. Hollomon and D. Turnbull, in Solidification of Metals and Alloys (New York AIME, 1951), p. 13. 

Directional solidification of metals and alloys is often performed with Bridgman type furnaces shown schematically in Figure 34.23. Such a furnace consists of a hot and a cold zone separated by an adiabatic zone. The temperature profile in a sample has a typical S-shaped profile (see Figure 34.25, right). The sample, being in a cartridge, is withdrawn with a fixed speed fi om the hot into the cold zone. 

From the beginning of the 1930s, studies on a melt treatment by elastic oscillations were carried out in three main directions (1) the study of an effect of elastic oscillations of various frequencies with the aim to establish a mechanism of nucleation and growth of solidification nuclei in supercooled liquids, i.e. melts and solutions (2) the study of structure and properties of metals and alloys subjected to low-frequency vibration and (3) the study of an ultrasonic oscillation effect on molten metals. Significant research in this area was performed in the 1950s by Danilov, Kapustin, Polotskii, Sirota, and their associates on solidification of organic substances and a number of metals in ultrasonic field. 

Processing of metals and alloys rapid solidification, C. Suryanarayana. In Material Science and Technology, a Comprehensive Treatment, 1991,15, 57-110, ed. R. W. Cahn, P. Haasen and E. J. Kramer. Weinheim VCH. 

Containerless processing is also of interest in physical metallurgy, as it provides opportunities to study thermophysical properties of high temperature metals and alloys, avoid sample contamination due to contact with container walls, and observe the solidification of materials that have been rapidly cooled from the melt. 

Numerous investigations on the ultrasonic treatment of molten ferrous and nonferrous metals and alloys were carried out in the 1960s. We should mention the works by Teumin and Abramov [6,8] on the basics of the ultrasonic treatment of a melt during solidification of ferrous metals and alloys, as well as the investigations by Balandin [9] on solidification of aluminum alloys. Further studies by Rostoker and Richards [10] and Seemann [11], and by a number of other scientists were devoted to the effect of UST on structure formation in nonferrous alloys. 

An interesting set of investigations on an effect of ultrasound with pulsed and continuous initiation of cavitation on solidification of low-melting metals and alloys has been performed by Buxmann [15] in Switzerland. The results of studies on the ultrasonic treatment of melts of aluminum and its alloys have been published... 

The formation of systems with solid backbones is often the result of aggregation processes taking place in suspensions and sols which lead to the development of spacial networks and final conversion of disperse systems into materials with valuable properties (Chapter IX, 2). In some cases, e.g. during solidification of metal alloys, the processes of structuring accompany formation of new phases. The systems with solid dispersion medium also form upon the solidification of a continuous phase in foams, emulsions, suspensions and sols. 

Foundries melt ferrous and non-ferrous metals and alloys and reshape them into products at or near their finished shape through the pouring and solidification of the molten metal or alloy into a mould. The foundry industry is a differentiated and diverse industry. It consists of a wide range of installations, from small to very large each with a combination of technologies and unit operations selected to suit the input, size of series and types of product produced in the specific installation. The organisation within the sector is based on the type of metal input, with the main distinction being made between ferrous and non-ferrous foundries. 

Abstract The science and technology underlying the process of melt atomization is introduced, paying particular attention to relevant thermal, solidification and other transport phenomena. Melt atomization has now been developed as one of major produce methods for various metal and alloy powder, and hence it is of both scientific and technological interest. The mechanisms of melt disintegration, the design of typical atomization devices, the influence of key process parameters, the thermal transport in the atomized droplets, and the characteristics of the size distribution are briefly described and discussed. 

Because the Hall-Peth law concerns only metals and alloys with the structure of solid solutions, therefore the solidification of alloys with eutectic transformation for example from Al-Si group in describing the influence of refinement of structure on the value of yield strength should take into account the value of interphase distance in eutectic (Paul et al., 1982 Tensi Horgerl, 1994 Treitler, 2005) ... 

Recent work ( ) has shown that there are transparent organic compounds which solidify in the same way that metals do. These organic compounds have been used as analogs to study the solidification behavior of metals The ability to observe directly the crystal growth processes in these transparent materials, together with their relatively low melting points, have permitted the elucidation of some of the phenomena which occur in metals and alloys. 

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