Metal alloying, development

The first metal alloy developed specifically for use in bone plates was vanadium steel, invented in about 1905. Over the next two decades, a number of other alloys and metals were tried as bone plate materials. In 1926, another alloy designed especially for bone plates was invented. It was a type of stainless steel consisting of 18 percent chromium and 8 percent nickel. Later the same year, a slightly modified form of the alloy was introduced, called I8-8SM0, containing a small amount of molybdenum. 

Pure metals, which are strictly chemical elements, are soft, exhibit low strength and have limited engineering applications. Alloys are materials composed of two or more chemical elements, at least one of which is a metal. Alloying develops properties that pure metals cannot achieve, such as strength, corrosion resistance or hardness. The terms metals and alloys are used interchangably. 

The first metal alloy developed specifically for human use was the vanadium steel which was used to manufacture bone fracture plates (Sherman plates) and screws. Most metals such as iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), titanium (Ti), tantalum (Ta), niobium (Nb), molybdenum (Mo), and tungsten (W), that were used to make alloys for manufacturing implants can only be tolerated by the body... 

Properties. Most of the alloys developed to date were intended for service as fuel cladding and other stmctural components in hquid-metal-cooled fast-breeder reactors. AHoy selection was based primarily on the following criteria corrosion resistance in Hquid metals, including lithium, sodium, and NaK, and a mixture of sodium and potassium strength ductihty, including fabricabihty and neutron considerations, including low absorption of fast neutrons as well as irradiation embrittlement and dimensional-variation effects. Alloys of greatest interest include V 80, Cr 15, Ti 5... 

Nonconventiona.1 Solder Systems. Nonconventional solder systems are developed for use with newer alloys, especially base metal alloys. They are few in number and will probably remain the exception rather than the rule. Some new solder systems consist of metallic particles either pressed to form a rod or suspended in a paste flux. The metallic composition is close to that of the alloy to be joined. If the particles are nonhomogeneous, the solder has particles with melting points lower and higher than that of the alloy. For nonhomogeneous solders, once the flame has been placed on the parts to be joined and the soldering material, it should not be removed until the flow process is completed. 

In the three decades following the publication of Rosenhain s book, the physieal science of metals and alloys developed rapidly, so that by 1948 it was possible for Robert Franklin Mehl (1898-1976) (see Smith 1990, Smith and Mullins 2001 and Figure 3.15), a doyen of American physical metallurgy, to bring out a book entitled A Brief History of the Science of Metals (Mehl 1948), which he then updated in the... 

On top of this alloy development, turbine blades for the past two decades have been routinely made from single crystals of predetermined orientation the absence of grain boundaries greatly enhances creep resistance. Metallic monocrystals have come a long way since the early research-centred uses described in Section 4.2.1. 

Some heat pumps, called thermoelectric heat pumps, employ the Peltier effect, using thermocouples. The Peltier effect refers to the evolution or absorption of heat produced by an electric current passing across junctions of two suitable, dissimilar metals, alloys, or semiconductors. Presently, thermoelectric heat pumps are used only in some specialized applications. They have not been developed to a point to make them practical for general heating and cooling of buildings. 

It should be noted that the data refer mostly to the behaviour of the alloys in H2SO4. Passivity is, however, influenced by the composition of the solution as well as that of the metal and for this reason the influence of alloying additions may be different in solutions containing other ions. In particular, CI and other similarly aggressive ions have a large influence and may prevent passivation, either completely or partially. If passivity cannot be maintained over the entire surface of the metal, pitting develops, and this is considered later. 

The determination of polarisation curves of metals by means of constant potential devices has contributed greatly to the knowledge of corrosion processes and passivity. In addition to the use of the potentiostat in studying a variety of mechanisms involved in corrosion and passivity, it has been applied to alloy development, since it is an important tool in the accelerated testing of corrosion resistance. Dissolution under controlled potentials can also be a precise method for metallographic etching or in studies of the selective corrosion of various phases. The technique can be used for establishing optimum conditions of anodic and cathodic protection. Two of the more recent papers have touched on limitations in its application and differences between potentiostatic tests and exposure to chemical solutions. ... 

The development of new products (which may be mixtures rather than pure materials, as for example a polymer composition, or a metallic alloy) also... 

The first use of lithium alloys as negative electrodes in commercial batteries to operate at ambient temperatures was the employment of Wood s metal alloys in lithium-conducting button-type cells by Matsushita in Japan. Development work on the use of these alloys started in 1983 [10], and they became commercially available somewhat later. 

Numerous atomization techniques have evolved for the production of metal/alloy powders or as a step in spray forming processes. Atomization of melts may be achieved by a variety of means such as aerodynamic, hydrodynamic, mechanical, ultrasonic, electrostatic, electromagnetic, or pressure effect, or a combination of some of these effects. Some of the atomization techniques have been extensively developed and applied to commercial productions, including (a) two-fluid atomization using gas, water, or oil (i.e., gas atomization, water atomization, oil atomization), (b) vacuum atomization, and (c) rotating electrode atomization. Two-fluid atomization... 

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