Electrodeposited Alloys and Multilayered Structures

It is general experience in materials science that alloy can exhibit qualities that are unobtainable with parent metals. This is particularly true for electrodeposited alloys, mainly due to formation of metastable phases and intermediate layers. Some important properties of materials, such as hardness, ductility, tensile strength. Young s modulus, corrosion resistance, solderability, wear resistance, antifriction service, etc., may be enhanced. At the same time, some properties that are not characteristic for parent metals, such as high magnetic permeability, other magnetic and electrical properties, amorphous structure, etc., can also be obtained. In some cases, alloy coatings may be more suitable for subsequent electroplate overlayers and conversion chemical treatments [1], 

Some alloys may be more easily obtained by electrodeposition than by metallurgical processes. This is particularly tme for alloys composed of metals having large differences in melting temperatures or metals that cannot be mixed in a liquid state. Such metals can very often be codeposited from the solutions (e.g., alloys Ag-Ni, Ag-Co, and Cd-Co). Taking into account that some metals cannot be electrodeposited from the aqueous solutions (Ti, V, W, Nb, Zr, etc.), they could be electrodeposited from the melts of their salts. In recent times, the processes of metal and alloy electrodeposition from the room-temperature molten salts were also investigated and developed (cf. electrodeposition of Al-Cu, Al-Co, Al-Ni alloys from AlCls-MeEtlmCl melt). 

The fast-growing requirements of modem industry for materials with special qualities in the last century have given rise to increasing interest in electrodeposition of alloys, particularly in corrosirai protection and in the modem electronic industry [1]. 

From 1842 until the end of the nineteenth century, over 180 alloys involving 40 elements have been electrodeposited [2]. An excellent review of the achievements up to 1962 is given in the book by Brenner [3], while from practical point of 

Concerning scientific approach of the electrodeposition of alloys, all the results obtained until 1995, mainly connected with the thermodynamics and kinetics of alloy electrodeposition, are summarized in the chapter by Despic and Jovic [1] and Jovic et al. [5]. In the present chapter, the morphology of electrodeposited alloys will be the main subject. 

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