Alloys composition specification

Continued additions of chromium will improve corrosion resistance in more severe environments, particularly in terms of resistance in oxidizing environments, at both moderate and elevated temperatures. Chromium contents in ferritic stainless steels are limited to approximately 28%. These alloys are known as 400-series stainless because they were identified with numbers begirming with 400 when AISI had the authority to designate alloy compositions. Specific members of the ferritic families will be covered in Chapter 7. 

The alloys of titanium utilised in industrial applications have compositional specifications tabulated by ASTM. The ASTM specification number is given in Table 14 for the commercially important alloys. MiUtary specifications are found under MIL-T-9046 and MIL-T-9047, and aerospace material specifications for bar, sheet, tubing, and wine under specification numbers 4900—4980. Every large aircraft company has its own set of alloy specifications. 

The alloy name in the United States can include a company name or trademark in conjunction with the composition for alloyed titanium or the strength, ie, ultimate tensile strength for Timet and yield strength for other U.S. producers, for unalloyed titanium. The common alloys and specifications are shown in Table 14. 

In any specific environment, only certain alloys are affected. Substitution of more resistant materials does not always necessitate major alloy compositional changes. Adding as little as a few hundredths of a percent of arsenic, for example, can markedly reduce dezincification in cartridge brass. Antimony and phosphorus additions up to 0.1% are similarly efficacious. 

Produced in this way, these materials can be less reliable, with the introduction of unwanted tramp elements. Where proving tests have indicated the suitability of a proprietary alloy for specific application, the same source of material should be used for construction. Published compositional data are typical values cast analyses should be requested for critical applications. 

In both aqueous and organic environments the crack velocity is related to the instantaneous stress intensity factor, as shown in Fig. 8.53. Three regions may be observed I, II and III. Regions I and III are not always observed and the specific relationship observed depends upon the alloy composition and heat treatment, the environmental composition and the experimental conditions. ... 

Rather than utilise a full thermodynamic calculation for their final sensitivity analysis, they fitted their calculated results to a formula which could be used within the composition specification range of Zeron 100 alloys, such that the fraction of austenite, P, was given by... 

Fig. 10. Activity parameters A and As as a function of alloy composition (at. % Cu). Upper curves Aw and A, are for cyclopropane at 90°C lower curves Aw and As are for propane at 320°C. A = log(a/w) A, = log(a/sw) a is conversion, s specific surface area of catalyst, iv weight of catalyst. From Beelen et al. (102).

Cadenhead and Masse (709) report similar results for the benzene hydrogenation. They stress the importance of measuring specific activities because plots of the surface areas versus alloy composition show a maximum (70S). For Pd-Cu and Pd-Au samples it is concluded (709) that the catalytic behavior found indicates the formation of ternary transition metal-group IB metal-hydrogen systems. 

At a selected alloy temperature the vapor pressure of cadmium is determined as a function of alloy composition the cerium solvent has a negligible vapor pressure. The alloy, located in one leg of a sealed inverted U-tube, is subjected to various specific pressures of cadmium from a supply of pure cadmium at selected temperatures in the second leg of the tube. The U-tube is freely suspended at its midpoint and connected to a balance, so that the transfer of cadmium from one leg of the tube to the other can be measured. This gives information as to the change in alloy composition and phase equilibrium. 

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