Type I alloys

Type II, medium-hard alloys, are harder, stronger, and have lower elongation than type I alloys. They are used for moderate stress appHcation, eg, three-quarter crowns, abutments, pontics, full crowns, and saddles. The type II gold alloys are difficult to burnish, and can usually be heat-treated. 

In general, for a mixture of two or more pure elements, there are two types of solid-solution alloys that may be obtained. Type I alloys are completely miscible with one another in both liquid and solid states. As long as the Hume-Rothery rules are satisfied, a random substitutional alloy will be produced. We will see many examples of these alloys in this section for a variety of metal dopants in stainless steels. By comparison, type II alloys are only miscible in the molten state, and will separate from... 

Figure 8.40 Schematic diagram to show the relationship of the different hot corrosion mechanisms as a function of temperature and SO3 pressure, (i) Type II, gas-phase induced acidic fluxing, (ii) At high SO3 pressures (PSO3 > 10 atm) pronounced sulphide formation accompanied by oxidation of sulphides and fluxing reactions, (iii) Type I (alloy-induced acidic fluxing basic fluxing, sulphidation).

We have dwelt at length on liquid Cu-Sn simply because so much information is available. For other liquids of type I alloys in which— is positive... 

Type I, soft alloys (20—22-carat golds), are used for inlays of simpler non-stress-bearing types. Type I gold alloys can be burnished, and are not heat-treatable. They are composed essentially of gold—silver—copper with minor modifying additions, eg, zinc. 

GoldJilloys, Wrought Type. Two types of wrought gold alloys were formerly recognized by the ADA specification no. 7 for the fabrication of orthodontic and prosthetic dental appHances, ie, type I, high-precious-metal alloys, and type II, low-precious-metal alloys (gold color). Alloys of this type are seldom used in the United States they have been replaced by stainless steels and nickel—titanium alloys. 

These three passive systems are important in the technique of anodic protection (see Chapter 21). The kinetics of the cathodic partial reaction and therefore curves of type I, II or III depend on the material and the particular medium. Case III can be achieved by alloying additions of cathodically acting elements such as Pt, Pd, Ag, and Cu. In principle, this is a case of galvanic anodic protection by cathodic constituents of the microstructure [50]. 

In addition to nickel alloys, nickel also forms an important alloying element in stainless steels and in cast irons, in both of which it confers additional corrosion resistance and improved mechanical and engineering properties, and in Fe-Ni alloys for obtaining controlled physical and magnetic properties (see Chapter 3). With non-ferrous metals nickel also forms important types of alloys, especially with copper, i.e. cupro-nickels and nickel silvers these are dealt with in Section 4.2. 

Alloy component (wt%) ASTM B4I8-88 Type I ASTM B4I8-88 Type II US Mil Spec. A I800I J DnV Recomm for elevated temp. 

If the binary constituents AC and BC both have the structure a as their stable form in the temperature range (7, then the alloy is of Type I and one observes a single Bravais lattice of the type a at all alloy compositions for which solid... 

A smaller class of type II alloys of II-VI binaries also exists, including the (CdS) ,(ZnSe)i (CdS) ,(ZnTe)i (CdSe) ,(ZnSe)i (CdS) ,(CdTe)i-. (CdSe)x(CdTe)i i , and (CdS) c(ZnS)i i systems, which transform at some critical composition from the W to the ZB structure. Importantly, the transition temperatures are usually well below those required to attain a thermodynamically stable wurtzite form for the binary constituents (e.g., 700-800 °C for pure CdS and > 1,020 "C for pure ZnS). The type 11 pseudobinary CdxZni jcSe is of considerable interest in thin film form for the development of tandem solar cells as well as for the fabrication of superlattices and phosphor materials for monitors. The CdSe Tei-x alloy is one of the most investigated semiconductors in photoelectrochemical applications. 

Figure 10.64 Schematic illustrations showing die microstructural evolution of three kinds of + 7 microstiuctures widmanstitten, type I lamellar and blocky type 2 lamellar stnictures in Ni-2SAl-(>)t8Fe, (b)lSFe and (c)13Fe alloys.

Method No 308. Delay Powder, Non-Gaseous (Zirconium-Nickel Alloy Type) Type I (delay 2-sec) - Ba chromate 60.0, 70/30 Zr-Ni alloy 26.0 8t K perchlorate 14.0% ... 

Specification Requirements for Type I and Type II Zirconium-Nickel Alloys. Z 25... 

Zirconium-Nickel Alloys. Zr/Ni 70/30 (Type I) and 30/70 (Type II) silvery white to grey cubic crystn pdrs d, 7.20g/cc (Type I), 8.10g/cc... 

The US military specification covering powdered Zr-Ni alloy is MIL-Z-11410B (12 Feb 1968) (Ref 4). The following requirements, shown in Table 1, apply to 70/30 Zr—Ni (Type I) and 30/70 Zr—Ni (Type II) alloys "Refs 1) Anon, Engrg Des Hndbk, Military Pyrotechnics Series, Part Three—Properties of Materials Used in Pyrotechnic Compositions , AMCP 706-187 (1963), 337 2) D. Zauder et... 

The range of coherence follows naturally from the BCS theory, and we see now why it becomes short in alloys. The electron mean free path is much shorter in an alloy than in a pure metal, and electron scattering tends to break up the correlated pairs, so dial for very short mean free paths one would expect die coherence length to become comparable to the mean free path. Then the ratio k i/f (called the Ginzburg-Landau order parameter) becomes greater than unity, and the observed magnetic properties of alloy superconductors can be derived. The two kinds of superconductors, namely those with k < 1/-/(2T and those with k > l/,/(2j (the inequalities follow from the detailed theory) are called respectively type I and type II superconductors. 

Type I zirconium-nickel alloy delay compn having a formulation 60/14/26 BaCr04/KClC>4/ 70-30 Zr-Ni was used for these expts. Two different radioactive tracers, 27-day chromium-51 and 2.1-year cesium-134, were employed. The first was added to the compn in the form of BaslCr04 as a fractional percentage of total barium chromate, and the second tracer was included as 134CsQ in ppm concn of the total mixt... 

Soft metallic elements such as Al, In, Pb, Hg, Sn, Zn, Tl, Ga, Cd, V and Nb are type I superconductors. Alloys and chemical compounds such as Nb3Sn, V3Ga, and lZa3In, and some transition elements, are type II superconductors. Type II substances generally have a higher Tc than do type I superconductors. The recently discovered transition metal oxide superconductors have generated intense interest because they are type II superconductors with very high transition temperatures. Table 13.1 summarizes Tc for selected superconductors. 

The preceding chapters have shown that the majority of metals can now be electrodeposited from ambient-temperature ionic liquids. However, this does not necessarily mean that the liquid with the widest potential window will negate the use of all other ionic liquids. Rather, it is most likely that ionic liquids will be task-specific with discrete anions being used for metals that cannot be electrodeposited from aqueous solutions such as Al, Li, Ti, V and W. Type I eutectics will probably be the most suitable for Al, Ga and Ge. Type II eutectics are most suitable for Cr and Type III are most suited to Zn, Cu, Ag and associated alloys. Type III will also find application in metal winning, oxide recycling and electropolishing. To date most practically important metals have been electrodeposited from ionic liquids and a comprehensive review is given in articles by Abbott [99] and Endres [100-102],... 

Details may be obtained from the magnesium alloy producers or from ASM Handbook, vol. 5, and Military Specification MIL-M-4502, Type I,... 

Binary and ternary alloys and oxides of these elements, as well as pure V, Nb, Gd, and Tc are referred to as Type II or high-field superconductors. In contrast to Type I, these materials exhibit conductive characteristics varying from normal metallic to superconductive, depending on the magnitude of the external magnetic field. It is noteworthy to point out that metals with the highest electrical conductivity (e.g., Cu, Au) do not naturally possess superconductivity. Although this behavior was first discovered in 1911 for supercooled liquid mercury, it was not until 1957 that a theory was developed for this phenomenon. 

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