Rapidly solidified alloy

The typical features of the phase diagram of Al-rare earth alloys are high liquid solubility, low solid solubility of rare earths and relatively low liquidus temperatures. The low diffusivity of rare earths in these alloys is an attractive feature from the point of view of the thermal stability of the dispersoids. 

Addition of Ce to rapidly solidified alloys of Al-Fe produces a product suitable for use at high temperatures. The heat treatable ingot metallurgical products are used up to 175°C. 

MODERN ASPECTS OF RARE EARTHS AND THEIR COMPLEXES 

On the other hand, rapidly solidified Al-Fe-Ce alloy retains its high strength up to 340°C. Addition of rare earths to Al-transition metal alloys shows a notable modification of micro structure resulting in improved strength and thermal stability as shown in Fig. 12.7. 

Effects of RE additions on the microstructure and mechanical properties of rapidly solidified Ti alloys. 

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Corrosion rates of atomized, rapidly solidified alloy cast and chill cast alloys are given in Table 4.73. The data show that atomized rapidly solidified alloy is comparable in corrosion resistance to the cast AZ ID alloys. Rapid solidification improves the corrosion resistance of the alloys since the homogeneous microstructures tend to disperse the elements and particles, which otherwise act as cathodic sites. Extended solubility of various elements may also shift the electrode potentials to more noble values. 

H. H. Liebermann eds, Rapidly Solidified Alloys Processes, Structures, Properties, Applications , Marcel Dekker, Parsippany, NJ, 1993. 

Modern Ceramic Engineering Properties, Processing, and Use in Design. Second Edition, Revised and Expanded, David N. Richerson Introduction to Engineering Materials Behavior, Properties, and Selection, G. T Murray Rapidly Solidified Alloys Processes Structures Applications, edited by Howard H. Liebermann Fiber and Whisker Reinforced Ceramics for Structural Applications, David Belitskus Thermal Analysis of Ceramics, Robert F. Speyer Friction and Wear of Ceramics, edited by Said Jahanmir... 

H. H. Liebermann, Rapidly solidified alloys, Marcel Decker, Inc., New York (1993). 

The method of liquid dynamic compaction (LDC) (Chin et al. 1986, Tanigawa et al. 1986) is based on the process of gas atomization (Anand et al. 1980). In gas atomization a stream of molten alloy is broken into a spray of fine particles by a jet of high-velocity gas and the rapidly solidified particles are collected. In LDC, a cooled substrate is placed beneath the atomization core at a distance such that most of the sprayed droplets are partially solidified. The rapidly solidified alloy builds up on the substrate at controllable rates, which can easily exceed 1 cm/min. Rapid solidification is made possible by the supercooling of the high-velocity atomized particles and the good thermal contact with a water-cooled copper substrate. 

Krishnamurthy et al. (1988 b) found significant refinement of microstructure in rapidly solidified alloys, with the maximum refinement occurring near the quenched surface of the ribbons. Anodic polarization of the ribbon showed a pseudo-passivation effect which led to a significantly lower current density. Hehmann et al. (1989) compared the corrosion of rapidly solidified Mg-Al alloys containing 10-24% Al in aerated 0.001 M NaCl solution with that of chill-cast alloys of the same composition. Electrochemical characterization revealed a... 

It seems that the temperature range for conventional unprotected (no surface coatings) solid-solution titaniiun alloys is upper limited to about600 °C [Ble85] and that futm e development shoiald include combinations of (1) inherently oxidation-resistant alloys, (2) coatings, (3) further development of the a2 phase and y-phase aliuninides and their variants, Euid (4) the use of rapidly solidified alloys. Figure 9.6 outlines the manner in which such developments proceed naturally out of the earlier work. 

Fro86] Froes, F.H. and Rowe, R.G., Rapidly SoHdified Titanium, in Rapidly Solidified Alloys and Their Mechanical and Magnetic Properties, B.C. Giessen, DJE. PoUc, and A.I. Taub, Ed., Vol 58, Materials Research Society, 1986, p. 309-343... 

Surface analysis of films formed transiently on bare, e.g., laser-irradiated surfaces [175], should be undertaken. Such studies should include rapidly solidified alloys that incorporate segregant elements and should be integrated with mechanical studies on die same films. 

Ioa] loannidis, E.K, Sheppard, T., Powder Metallurgy Aluminium Alloys Characteristics of an Al-Cr-Fe Rapidly Solidified Alloys , J. Mater. Science, 25, 3965-3975 (1990) (Crys. Stmcture, Morphology, Experimental, 15)... 

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