Solidified eutectic

The eutectics examined and their melting points are given in Table 3.1. The compounds were melted in 10 mm inner diameter pyrex tubes, and polished sections were prepared from the solidified eutectic samples. 

The same authors examined the rate of detonation of a molten and solidified eutectic comprising 58% of trinitrotoluene and 42% of substance (I), and obtained a value of approximately 7000 m/sec. 

The product of this reaction appeared to have smaller particles than the original uranium dioxide, which settled rapidly to the bottom of the reaction tube. These particles were recovered by aqueous dissolution of the solidified eutectic and filtration of the insoluble uranium-containing species. No hydrolysis of the insoluble uranium-containing species is believed to occur with aqueous dissolution of the salt matrix. To preclude hydrolysis in experiments where it was more likely, the nitrate salts were dissolved in 0.5 M HNO3. 

Calderon-Moreno, J.M. and Yoshimura, M., Rapidly solidified eutectic composites in the system Al203-Y203-Zr02 Ternary regions in the subsolidus diagram, Solid State Ionics 154-155 (2002) 311-317. 

Figure 13. Temperature dependence of thermal expansion coefficients of Ti5Si3, the hypoeutectic Ti-Si7.5-All alloy and the unidirectionally solidified eutectic Ti-Ti5Si3...

The elastic moduli vs. temperature curves of the hypoeutectic Ti-Si7.5-All alloy and of the directionally solidified eutectic a-Ti-Ti5Si3 composite with discontinuous Ti5Si3 fibers -aspect ratio of lf/df 50- are depicted in fig. 14. In comparison the temperature-dependent Young s modulus of the polycrystalline Ti5Si3 compound is also shown in the diagram. A detailed description and discussion of the elastic moduli of the pure silicides is given in section 4.3. 

FIGURE 3-21 One-hour bend stress relaxation ratio for directionally solidified eutectic YAG/alumina fibers grown by edge-defined film growth (EFG), for polycrystalline alumina-based fibers, and for c-axis sapphire fibers. Source Morscher et al., 1995. 

In practice, materials display one of two different types of freezing behavior (a) the liquid phase suddenly solidifies (eutectic formation) at a temperature that depends on the nature of solids in the sample, or (b) the liquid phase does not solidify (glass formation), but rather it just becomes more and more viscous until it finally takes the form of a very stiff. 

If the interfacial energy between the a and P phases is low compared to the liquid-a and liquid- interfacial energies, then the a and P phases will prefer to wet each rather than the liquid. As shown in Figure 6.36b, this can lead to the coordinated growth of long alternating lamellar or plateletlike formations of the a and P phases. Such lamellar microstmctures commonly occur for rapidly solidified eutectic phase transformations where insufficient time is provided to approach a more equilibrium microstructure. 

A particular type of fibre-reinforced composite is the directionally solidified eutectics in which matrix and reinforcement are made in one single process from one or two different materials. The reinforcement usually has the form of plates or rods and their orientation may be designed and controlled in the solidification process. Only the volume fraction of the reinforcement cannot be designed arbitrarily and is determined by the applied technological processes. 

The AlSi-alloy types are optimally castable because of the solidified eutectic at a low temperature of 570 °C (at 12.5% Si in the Al-base compound). They are particularly suitable for castings with large wall thickness variations and thin ribs. The alloy is very soft and tends to smear when machining. The corrosion resistance is described as good, if free of copper. The addition of Mg or Cu to the Al-Si alloys causes harden-ability and thus an increase in strength. The three-component alloys are also easy to cast, can also be better machined because of their higher hardness, and can be well protected by anodic oxidation. The copper-containing alloys if unprotected are more susceptible to corrosion than copper-free versions. 

Charles C. Sorrell, Vladimir S. Stubican, Richard C. Bradt. Mechanical Properties of ZrC-ZrB2 and ZrC-TiB2 Directionally Solidified Eutectics. Journal of the American Ceramic Society 1986 69 3I7. 

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