The Structure of Castings

Boyle, A. "The Structure of Cast Iron" American Society... 

The carbon content of cast irons is generally between 2 and 4%. They are generally cheap, easy to melt and cast, with high damping capacity and very good machinability. Cast irons are classified as either white or gray. These terms arise from the appearance of a fieshly fractnred surface. The structure of cast irons is affected by the following factors ... 

Limitations on the use of cast irons are similar to those for steel, since in many environments most cast iron has poor corrosion resistance. Most grades are also susceptible to graphitization (the loss of iron, leaving a weak structure of graphite) in acidic environments below a pH of approximately 5.5. This attack occurs in soils. 

Detailed consideration of the structure of many of the advanced and complex alloys which are of considerable technological importance (high-strength titanium alloys, nickel-base superalloys, etc.) is beyond the scope of this section, other than to point out that no new principles are involved. Certain titanium alloys, for example, exhibit a martensitic transformation, while many nickel-base superalloys are age hardening. Similarly, cast irons, although by no means advanced materials, are relatively complex they are considered in Section 1.3 where graphitisation is discussed. 

The structures of the solids isolated from strongly alkaline solutions cast a shadow of doubt over the simple model in which the only species formed are Be(OH)3 and BelOH) . Of course what crystallizes from a solution may well be a species with low equilibrium concentration as the process of crystallization is driven by the insolubility of the product. Nevertheless it is clear that relatively little effort has... 

The concepts and techniques discussed by Cirkel and Okada are relevant with a view toward modifying the structure of solution cast Nafion membranes by manipulating counterion type, solvent, temperature, and other variables. 

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