Intermetalhc alloys

Figure 10.65 Calculated mole % phase vs temperature plots for Ni-AI-Tt intermetalHc alloys, (a) Ni-28AI-12Ti, (b) Nt-22AI-l5Ti and (c) Ni-20AI-l3Ti.

G. Frommeyer and R. Rablbauer in Defect Properties and Related Phenomena in Intermetalhc Alloys, eds. E. P. George, H. Inui, M. J. Mills G.Eggeler, Mat. Research... 

McKee DW (1993), Oxidation and protection of Ti3Al-based intermetalhc alloys . Mat. Res. Soc., Symp. MRS, 288, 953-958. 

The electrodeposition of Cr in acidic chloroaluminates was investigated in [24]. The authors report that the Cr content in the AlCr, deposit can vary from 0 to 94 mol %, depending on the deposition parameters. The deposit consists both of Cr-rich and Al-rich solid solutions as weU as intermetalHc compounds. An interesting feature of these deposits is their high-temperature oxidation resistance, the layers seeming to withstand temperatures of up to 800 °C, so coatings with such an alloy could have interesting applications. 

Transition-element chalcogenides are also best prepared by direct reaction of the elements at 400-1000° C in the absence of air. They tend to be metallic nonstoichiometric alloys though intermetalhc compounds also occur, e.g. Ti...2Se, Ti-sSe, TiSeo.95, TiSei.os, Tio.gSe, Ti3Se4, Tio.vSe, TisSeg, TiSe2, TiSes, etc. ... 

Most barium compounds are not as thermodynamically stable as the corresponding compounds of magnesium and calcium and therefore can be reduced by these metals. However, rather than producing pure barium, barium alloys are formed. Barium combines with most metals, forming a wide range of alloys and intermetalhc compounds. Among the phase systems that have been better characterized are those with Ag, Al, Bi, Hg, Pb, Sn, Zn, and the other Group 2 metals (12). 

FFC is enhanced when aluminum is alloyed especially Cu and Fe have a detrimental effect on FFC resistance due to the existing intermetalhc particles (IMPs) see Ref. [168] and references therein. 

Sun2] Sundar, R.S., Deevi, S.C., Effect of Heat-Treatment on the Room Temperature Ductility of an Ordered Intermetalhc Fe-Co-V Alloy , Mater. Sci. Eng. A, 369(1-2), 164-169 (2004) (Experimental, Meehan. Prop., Morphology, Phase Relations, 22)... 

And] Andrews, K.W., A New Intermetalhc Phase in Alloy Steels , Nature, 164, 1015-1015 (1949) (Crys. Stracture, Experimental, 2)... 

In 1961 a naval engineer, William J. Buechler, made an unexpected and fortunate discovery. In searching for the best metal to use in missile nose cones, he tested many metal alloys. One of them, an intermetalhc compound of nickel and titanium, NiTi, behaved very oddly. When he struck the cold metal, the sound was a dull thud. When he struck the metal at a higher temperature, however, it resonated like a beU. Mr. Buechler knew that the way in which sound propagates in a metal is related to its metallic structure. Clearly, the structure of the NiTi alloy had changed as it went from cold to warm. As it turned out, he had discovered an alloy that has shape memoiy... 

In recent years, alloying and processing have been used to control the ordered crystal structure, microstructural features, and grain boimdary structure and composition to overcome the brittleness inherent to ordered intermetalhcs (Ref 1-3). Success in this work has inspired parallel efforts aimed at improving strength properties. The results have led to the development of a number of attractive intermetfdlic alloys with useful ductihty and strength. 

Information in the datasheets Titanium Aiuminides, TisAl Alloys, and Gamma Alloys was extracted from the article Ordered Intermetalhcs by C.T. liu, J.O. Stiegler, and EH. Froes, in ASM Handbook, Vol 2, 1990, with additional information from S.C. Huang, B. Marquardt, and R.G. Rowe of General Electric Company. 

This is the result of a redueed concentration of Au and a high concentration of Pd at the leading edge of Al. Instead of void formations, a stable Al—Pd-Au intermetalhc phase is formed which has high electromechanical integrity. Therefore, Au-Pd alloys are typically employed for Al wire bonding apphcations and can be die-bonded under suitable conditions (organic). 

It was proposed by Lamaka et al. that salicylaldoxime, 8-hydroxyquinoline and quinaldic acid provided corrosion protection to AA2024 by forming a thin organic layer of insoluble complexes on the alloy surface, thereby suppressing the dissolution of Mg, A1 and Or from intermetalhc particles (Fig. 4.2). Protective organic layers on the surface of AA2024 were also formed when treated with tiiazole and thiazole derivatives, as reported by Zheludkevich et and decreased the rate of both the anodic and cathodic processes. 

For precipitation hardenable alloys, the size and distribution of intermetallic precipitates depends on the quenching and artihcial ageing conditions. The continuous precipitation of intermetalhcs at grain boundaries can thus be avoided. 

Lanthanides, especially cerium, fulfil the basic requirements for alternative corrosion inhibitors the ions form insoluble hydroxides, which enable them to be used as cathodic inhibitors they have a low toxicity and are relatively abundant in nature. Cerium has a high afimity for oxygen and the bond between cerium and oxygen is unlikely to be broken under the potentials applied. For some aluminium alloys, cerium precipitation from aqueous solutions of cerium salts was observed on cathodic intermetalhc compounds and in some instances, the oxide covered the entire specimen surface [14-19]. 

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