These substances are composed of metals other than iron. However, these may contain iron in small proportion. Six non-ferrous materials are available in sufficient quantity reasonably at low cost and used as common engineering metals. These are aluminium, tin, copper, nickel, zinc, and magnesium. Some other non-ferrous metals, about 14 in number, are produced in relatively small quantities but these are of vital importance in modern industry. These include chromium, mercury, cobalt, tungsten, vanadium, molybdenum, antimony, cadmium, zirconium, beryllium, niobium, titanium, tantalum, and manganese.
Aluminium Alloys: Aluminium alloys have high thermal and electrical conductivities, and good corrosion resistant characteristics. As Al has FCC crystal structure, these alloys are ductile even at low temperatures and can be formed easily. However, the great limitation of these alloys is their low melting point (660°C), which restricts their use at elevated temperatures. Strength of these alloys can be increased by both cold and heat treatment—based on these alloys are designated into two groups: cast and wrought. Chief alloying elements include Cu, Si, Mn, Mg, Zn. Recently, alloys of Al and other low-density metals like Li, Mg, Ti gained much attention as there is much concern about vehicle weight reduction. Al–Li alloys draw much more attention of metallurgy especially as they are very useful in aircraft and aerospace industries. Common applications of Al alloys include beverage cans, automotive parts, bus bodies, aircraft structures, etc. Some of the Al alloys are capable of strengthening by precipitation, while others have to be strengthened by cold work or solid solution methods.
Copper Alloys: As history goes by, bronze has been used for thousands of years. It is actually an alloy of Cu and Sn. Unalloyed Cu is soft, ductile, thus hard to machine, and has virtually unlimited capacity for cold work. One special feature of most of these alloys is their corrosion resistant in diverse atmospheres. Most of these alloys are strengthened by either cold work or solid solution method. Common Cu alloys are: brass, alloys of Cu and Zn where Zn is substitutional addition (e.g., yellow brass, cartridge brass, muntz metal, gilding metal); bronze, alloys of Cu and other alloying additions like Sn, Al, Si, and Ni. Bronzes are stronger and more corrosion resistant than brasses. Mention has to be made about beryllium coppers which possess combination of relatively high strength, excellent electrical and corrosion properties, wear resistance, can be cast, hot worked, and cold worked. Applications of Cu alloys include costume jewellery, coins, musical instruments, electronics, springs, bushes, surgical and dental instruments, radiators, etc.
Magnesium Alloys: The most sticking property of Mg is its low density among all structural metals. Mg has HCP structure, thus Mg alloys are difficult to form at room temperatures. Hence Mg alloys are usually fabricated by casting or hot working. As in case of Al, alloys are cast or wrought type, and some of them are heat treatable. Major alloying additions are Al, Zn, Mn, and rare earths. Common applications of Mg alloys include hand-held devices like saws, tools, automotive parts like steering wheels, seat frames, electronics like casing for laptops, camcoders, cell phones, etc.
Titanium Alloys: Ti and its alloys are of relatively low density, high strength, and have very high melting point. At the same time they are easy to machine and forge. However, the major limitation is Ti’s chemical reactivity at high temperatures, which necessitated special techniques to extract. Thus, these alloys are expensive. They also possess excellent corrosion resistance in diverse atmospheres, and wear properties. Common applications include space vehicles, airplane structures, surgical implants, and petroleum and chemical industries.
Refractory Metals: These are metals of very high melting points. For example, Nb, Mo, W, and Ta. They also possess high strength and high elastic modulus. Common applications include space vehicles, X-ray tubes, welding electrodes, and where there is a need for corrosion resistance.
Leave a Reply