Studied by 19 people
Extracting metal from ore
Are not naturally found in their pure form but rather as an ore consisting of a carbonate, oxide or sulphide, and often in combination with other metals
Crystal Structures for metals
body centred cubic (BCC) face centred cubic (FCC) close packed hexagonal (CPH)
Importance of Grain Size
It influences the yield strength, impact toughness, elongation, and creep resistance. The grain size of a metal can be influenced in a number of ways, the most common of which involves plastic deformation followed by heat treatment to encourage recrystalization.
Work Hardening
Also known as strain hardening or cold hardening is the phenomenon in which the material is strain hardened during cold work. This effect is considered to be the result of increasing resistance to slip within the grains of a polycrystalline material
Alloying
Is the phenomenon in which metallic elements other than those of the base metal are intentionally incorporated into the crystal lattice of the base metal. Through this process properties are changed and improved, such as increased yield strength and tensile strength
Hardening
When metals such as steel undergo a heat treatment, in which an item is raised to an elevated temperature (typically >800degrees) and cooled rapidly by plunging it into a suitable quenching medium, hardness and strength are significantly increased.
Tempering
Steel with increased hardness (after being hardened) it has decreased ductility and impact toughness - the metal is said to be brittle. In order to regain some ductility, a low temperature heat treatment if often employed immediately following the quench hardening operation. This heat treatment reduces strength slightly while also reducing internal stresses and increasing ductility and toughness
Design Criteria for Superalloys
excellent high temperature strength
resistance to thermal shock along
high oxidation resistance
maintaining strength even at temperatures approaching a high fraction of their melting point
Groups of Superalloys
the superalloys all exhibit a face centred cubic (FCC) structure and typically fall into three groups: Iron-Nickel based alloys Nickel based alloys Cobalt based alloys
Creep
Is a process in which a material subjected to an applied load, lower than the yield strength, will over time, elongate or undergo strain. The rate at which creep will occur is dependant on both the applied stress and the operating temperature Creep occurs as a result of thermal vibrations over time.
Superalloy applications
jet and rocket engines
chemical plants where mechanical strength at elevated temperature, and resistance to corrosive atmospheres and oxidation resistance is necessary
biomedical application due to the high corrosion resistance and biocompatibility of the cobalt based alloys
Recovery and Disposal of Metals and Metallics Alloys
Is an important part of the material life cycle . It is often defined as the series of activities, including collection, separation, and processing, by which products or other materials are recovered from the solid waste for use in the form of raw materials in the manufacture of new products
Recycling Metal vs Metal Ore
From the standpoint of energy consumption, the manufacture of metal from its scrap is much more advantageous than manufacture based on smelting of the metal ore, and well established avenues exist for the recovery and reuse of the commonly used metals such as steel, aluminium and copper
Aluminium Production
Remains one of the most energy intensive materials to produce. It's production is the largest consumer of energy on a per-weight basis and is the largest electrical energy consumer of all industries.
Recycled Aluminium
Requires less than 6% of the energy needed to produce aluminium from mined materials and thus provides significant cost and environmental benefits
E-waste and Recycling Schemes
Many countries now operate recycling schemes directed specifically at this electronic waste or e-waste. A large trade has developed in e-waste recycling in which consumer electronics are exported to developing countries for disassembly. In these countries, recovery of metals is often performed without the environmental and health safeguards expected in developed countries
E-waste
Many of the materials found in it are expensive such as platinum and silver, and their recovery offers a considerable cost savings. Still others such as mercury, lead, arsenic, and cadmium can pose health problems if allowed to leach into the environment from landfills.
Blast furnace
Used to heat coke and lime stone. Iron is extracted in ore from four blast furnaces.
Extrusion
When a softened blank of a metal or plastic material is forced through a shaped metal piece to produce a continuous ribbon of the formed product.
gradual cooling
A few crystals are formed - large grain size
rapid cooling
Many crystals formed - small grain size
alloy
A metal combined with other substances which result in superior properties such as: strength, hardness, durability, ductility, tensile strength and toughness.
work hardening
Cooling the metal very slowly and hitting it with a hammer repeatedly. Forms smaller crystals which make the metal stronger.
Quenching
Heating a metal to a moderate temperature and then cooling it quickly. Small crystals form making metal harder but brittle.
creep resistance
the phenomenon of continuing plastic strain over long periods of time at loads below the yield point. Creep only happens at high temperatures
resistance to corrosion & oxidation resistant the ability of metallic materials to resist chemical degradation of the surface caused by the action of air or other gaseous mediums at high temperatures.
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