Alloying elements effect

Sch] Schurmann, V.E., Kramer, D., The Effect of Temperature and Equivalence of Alloying Elements Effects on the Carbon Solubihty in Iron rich Carbon-Saturated Multicomponent Melts (in German), Giessereiforschung, 21(1), 29-42 (1969) (Thermodyn., Review, Calculation, 35)... 

The effect of different types of reinforcement constituents on MMC corrosion behavior is discussed below. Due to the limited amount of information on MMC corrosion behavior, it is not feasible to have septunte sections for effects of alloying elements, effects of microstructure, sensitivity to acidity/alkalinity, etc. MMCs are relatively new and specialized materials therefore, only a limited number of corrosion studies have been conducted. Most studies relate the effects of the reinforcement constituents to overall MMC corrosion behavior. 

For the same lattice strains, the larger the valency difference between solute and solvent, the greater the hardening. The strengthening influence of alloying elements persists to temperatures at least as high as 815°C. Valency effects may be explained by modulus differences between the various alloys... 

Steels having adequate hardenabiHty develop martensitic stmctures in practical section sizes. Molybdenum is a potent contributor to hardenabiHty, and has been shown to be even more effective in the presence of carehiUy selected amounts of other alloying elements (26). The end-quench test has become the accepted method for measuring hardenabiHty, and the data can be correlated with section size. Technical societies worldwide have standardized hardenabiHty limits (bands) for a large number of carbon and alloy steels standards of the Society of Automotive Engineers are examples (27). 

Fig. 6. Effect of alloying elements on the phase diagram of titanium (a) a-stabilized system, (b) P-isomorphous system, and (c) P-eutectoid system.

The important (3-stabilizing alloying elements are the bcc elements vanadium, molybdenum, tantalum, and niobium of the P-isomorphous type and manganese, iron, chromium, cobalt, nickel, copper, and siUcon of the P-eutectoid type. The P eutectoid elements, arranged in order of increasing tendency to form compounds, are shown in Table 7. The elements copper, siUcon, nickel, and cobalt are termed active eutectoid formers because of a rapid decomposition of P to a and a compound. The other elements in Table 7 are sluggish in their eutectoid reactions and thus it is possible to avoid compound formation by careful control of heat treatment and composition. The relative P-stabilizing effects of these elements can be expressed in the form of a molybdenum equivalency. Mo (29) ... 

Mechanical properties depend on the alloying elements. Addition of carbon to the cobalt base metal is the most effective. The carbon forms various carbide phases with the cobalt and the other alloying elements (see Carbides). The presence of carbide particles is controlled in part by such alloying elements such as chromium, nickel, titanium, manganese, tungsten, and molybdenum that are added during melting. The distribution of the carbide particles is controlled by heat treatment of the solidified alloy. 

Effect of Various Alloying Elements. The mechanical properties of cast copper alloys are a function of alloying elements and their concentrations. The specific effects of a number of these alloying elements are given in the following sections. 

The addition of small amounts of alloying materials greatly improves corrosion resistance to atmospheric environments but does not have much effect against liquid corrosives. The alloying elements produce a tight, dense adherent rust film, but in acid or alkaline solutions corrosion is about equivalent to that of carbon steel. However, the greater strength permits thinner walls in process equipment made from low-alloy steel. 

Carbon is the cheapest and most effective alloying element for hardening iron. We have already seen in Chapter 1 (Table 1.1) that carbon is added to iron in quantities ranging from 0.04 to 4 wt% to make low, medium and high carbon steels, and cast iron. The mechanical properties are strongly dependent on both the carbon content and on the type of heat treatment. Steels and cast iron can therefore be used in a very wide range of applications (see Table 1.1). 

Figure 21-6 shows the possibility of reducing the overvoltage of cathodic hydrogen evolution. One can also reduce restrictions in the O2 reduction hy using copper in lead alloys. Such alloying elements can be very effective because they... 

Compensation of Preferential Sputtering. The species with the lower sputter yield is enriched at the surface. This effect is called preferential sputtering and complicates, e. g.. Auger measurements. The enrichment compensates for the different sputter yields of the compound or alloy elements thus in dynamic SIMS (and other dynamic techniques in which the signal is derived from the sputtered particles, e.g. SNMS, GD-MS, and GD-OES), the flux of sputtered atoms has the same composition as the sample. 

Chromium is the most effective alloying element for promoting resistance to oxidation. Table 3.10 gives temperatures at which steels can be used in air without excessive oxidation. In atmospheres contaminated with sulfur, lower maximum temperatures are necessary. 

The addition of alloying elements to the commercially pure metal results in an increase in its strength and usually has some favorable effects on other characteristics. 

Dezincification of a-brass can be readily prevented by suitable alloying additions, and this was achieved first by adding 1% Sn. However, elements such as As, Sb and P are more effective, and alloying additions of 0-02-0-06% As are widely used for this purpose. Unfortunately, no alloying element has been found that prevents the dezincification of the two-phase ai3-brasses, which are more susceptible than the a-brasses, and their use must be avoided under environmental conditions that are conducive to dezincification. 

Tomashov, N. D., Chernova, G. P. and Marcova, O. N., Effect of Supplementary Alloying Elements on Pitting Corrosion Susceptibility of 18Cr-14Ni Stainless Steel , Corrosion, 20, 166 (1964)... 

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