Introduction
Metallurgy may be defined as the art & science of making, shaping & treating of metals. The history of metallurgy is nearly as old as human civilization. Soon after the early Stone Age, man discovered metals, either in native forms, as gold, silver& copper, or formed by accidental processes of fire etc., like bronze. These metals were crudely shaped by artisans, who also developed rudimentary extractive processes using simple furnaces. Rig Veda written over 5000 years ago mentions several metals like gold, copper & iron. Gradually more sophisticated methods of extraction and treatment of metals started evolving. At the time of the invasion of Alexander, India had developed technologies to produce iron, which was considered very precious. Damascus swords were processed from wootz steel, originally produced in puddle furnaces in India from around 300 B.C., & underwent special heat-treatments to give its famous texture & sharpness. By the 4th century AD India had the capability of producing massive iron structures like the Iron pillar in Delhi, which remains intact even today because of its exceptional corrosion-resistance. The science of Metallurgy evolved from late 18th century onwards and the scientific principles behind extraction, purification, shaping & treatments were established. The advent of the optical microscope enabled people to see the internal structure of the metal at the micron level.
The Present Scenario
Iron and various steels became the backbone of human civilization. Extractive metallurgy dealing with the production of metals has become one of the largest industries in many countries. Large tonnages of iron & steel materials are being produced in huge blast furnaces and converters, employing thousands of people, enormous amounts of raw materials, fuels and water. Non-ferrous metals like copper, nickel, aluminum, magnesium, zinc, & titanium are being produced in large tonnages to meet the requirements of the various industries. Scientifically based new technologies of extraction evolved for more and more metals. Physical metallurgy made tremendous advancement in the last century. Sophisticated electron microscopes extended the range of observation of the internal structure of metals to the Nano-level, and today we have devices like the Field-ion microscope & Atomic force microscope to pinpoint atoms in metals and alloys. Principles of alloying and heat treatments were developed, enabling us to alloy and heat treat metals to get the desired combination of structure and properties. Processing technologies like casting, forging, rolling, extrusion, & wire-drawing, process metals & alloys to the desired forms & shapes. Super alloys based on nickel, stainless & maraging steels, age-hardened high strength aluminum alloys, & sophisticated titanium & zirconium alloys are being used in aerospace, transportation, power-generation & distribution, and chemical industry. Platinum, Gold. Uranium and the large group of Rare-earth metals are being extracted and used for the ever-growing electronics industry, nuclear industry & petroleum refining. Sophisticated welding technologies like electron-beam welding, laser welding & plasma welding are being used to produce flawless joints in critical applications in aerospace & nuclear industries. Near net-shaped products are being manufactured using powder metallurgy technologies.
Requirements in the aerospace industry led to the development of strong, tough & light aluminum alloys, titanium alloys and ultra-high strength steels. Nuclear industry necessitated the development of radiation-resistant & strong steels, nickel alloys & zirconium alloys and a whole range of fabrication technology for the fuel rod manufacture. Chemical, fertilizer & petrochemical industries led to development of high temperature & corrosion resistant super alloys, titanium alloys and stainless steels.
Many people believe that the level of development of a society is directly related to the consumption of steel & other metallic materials by that society. This is because of the enormous capacity of the metals industry to employ people and the vastness of the consumption of natural resources like minerals, water & fuel, which in turn requires the development of industries like mining, transportation, power generation and other infrastructures.
Future of Metallurgical Engineering
Despite the fact that many non-metallic materials like fiber-reinforced plastics & high-performance ceramics are replacing metallic materials in several industries, the requirements of steels, aluminum alloys, nickel alloys, copper alloys and other metals are expected to increase in the future. Iron & steels still constitute the major consumption of metallic materials in all the major industries. Newer metals like aluminum, magnesium, titanium & zirconium are also expected to be used in increasing quantities, in the future.
Extractive Metallurgy
Extraction of bulk metals like iron, aluminum, copper, zinc etc. requires large quantities of water & energy, besides man-power. Many of these operations emit polluting gases and liquid effluents which damage the environment & health of the workers. Extraction of nuclear materials and rare-earth metals involves additional radiation hazards to workers. Future developments to reduce the pollution levels, conservation of natural resources, & elimination of health hazards of workers are essential. Popular resistance to the use of fertile land for mining of minerals and setting up of extraction plants will increase in the future, and proper measures will have to be adopted to minimize the requirements of land, water and other resources. Useable mineral resources are getting depleted fast and viable technologies have to be developed to use leaner ores in an economic fashion. Recycling is a good source of many metals, particularly the rare-earths, the precious metals, & scarce metals like nickel & uranium. In the future, development of cost-effective and viable technologies for collection & re-use of such metals will be essential. The importance of this aspect may be understood from the fact that in Japan alone, recycling of used electronic gadgets will supply about 300,000 tons of rare-earth metals.
Rare-earth metals are essential components of many gadgets and equipment like iPhones, wind turbines, electric cars, robots, magnets, fluorescent lamps, & guided- missiles. Though the mineral resources of rare-earths are quite widely distributed, their extraction technology is highly complicated, and is the monopoly of a few countries. Because of the strategic importance of these metals, it is essential that the extraction technology must be more widely available. The environmental hazards of extracting rare-earths require special attention & efforts are needed to reduce or eliminate these hazards. Newer, more environment-friendly methods must be developed & widely disseminated. Professor I.V. Gorynin of the Central Research Institute of Construction Materials ,St. Petersburg, Russia recently stated; “Development of new technologies, including nanotechnology, should change the traditional metallurgy: mining, coke production, blast furnace, converter processes. In future, the possibility opens to replace non-ecological metallurgical processes by new methods of obtaining materials and products. It should be possible to create new environmentally friendly methods of the production of materials, other than the traditional methods of metallurgy”.
Physical Metallurgy
The advent of “Nano-materials” in recent years has opened up tremendous opportunities to develop new metallic materials with required properties. Conventional alloy development involves the creation of high strength by increased alloying, by plastic deformation, or by thermal treatments. But these methods lead to a reduction in the toughness, i.e., fracture resistance in presence of loads, of the material. Contrarily, nano structured metals with grain sizes in the nanometre range provide high strength & toughness. Technologies will have to be developed to create nanostructures in commercially used sizes of common metals and alloys. This will reduce the use of costly or scarce alloying elements, and environmental hazards involved in traditional metallurgical production. Computer algorithms may be developed to produce a desired alloy by picking atoms of different metals and building up the alloy structure. Near-net shaping of components using powder metallurgy is another development which will drastically reduce the energy consumption involved in traditional metallurgy. Thermal and thermo-mechanical treatments used in traditional metallurgy to produce & control microstructure & strength in metallic materials should be improved to reduce cost and environmental degradation. Severe plastic deformation, controlled heat treatments, laser processing are some of the other areas for future development.
Energy production from fossil fuels will eventually be discontinued due to depletion. Also such technology pollutes the environment significantly. Renewable sources of energy, like the sun, wind, and water are being explored to produce energy for the world. Search for viable energy production technologies based on solar energy, wind energy and hydrogen is steadily progressing. The technologies to be developed in future should be able to meet the world requirement of energy through cost-effective and non-polluting processes. Many metals will be required to operate such technologies. Besides the structural requirements, we need a wide range of metal-based catalysts, and hydrogen-storage materials. Stainless steels, titanium, platinum, & rare-earth metals are expected to play vital roles in such technologies.
Conclusion
The above and other new breakthrough approaches in metallurgical engineering are expected to provide humanity fundamentally new products of highest quality, employing much fewer workers & using ecologically clean methods. Such materials are expected to reduce the metal consumption of structures, and increase their life. Conservation of natural resources & reduction in environmental damage are the other benefits expected from these future developments.
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