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Metallic Properties Hardness Brittleness Malleability Ductility Elasticity Toughness Density Fusibility Conduction Contraction and Expansion Strength Corrosiveness
Introduction Crystallinity – degree of structural order of atoms in solids. Metals in gaseous and liquid state have no crystallinity.
Introduction ALLOYS – melting together of two metals to form a homogenous liquid.
Introduction Most of the industrially important alloys are based on 8 relatively cheap and abundant ones: IRON LEAD COPPER ZINC TIN NICKEL MAGNESIUM ALUMINUM
Treatment of Metals HOT AND COLD WORKING – deformation of metals or alloys in the cold as by rolling, stamping, swaging or drawing results in an increase in hardness and tensile strength and a decrease in ductility
Treatment of Metals HEAT TREATMENT– controlled heating and cooling of metals to alter their mechanical and physical properties without changing the product shape Purpose: Hardening Softening Material Modification
Treatment of Metals Hardening – increase in strength and wear Direct hardening Quench hardening Softening – reduce strength and hardness, restore ductility Annealing and recrystallization (50° C or 122°F) Normalizing (60°C or 140°F) Tempering (40°C or 104°F after quenching) Material modification– modify properties of materials Stress Relief
Ferrous Alloys - IRON Blast furnace Coke oven Limestone Iron ore Cast Iron Pig iron
Ferrous Alloys - Iron Cast iron - is roughly, the pouring of melted iron grades to patterns which would produce fine metal forms. Ordinarily, it is produced with Carbon to Iron ratio of more than 2% up to 4.5%. Cast Steel - is ordinarily, much lower in carbon than iron running from 0.2% to 0.35%
Ferrous Alloys - Steel STEEL - is primarily made from pig iron plus scrap melted into open-hearth furnace with flux and generally contains 0.05% to 2.0% Carbon. Plain Carbon Steels – iron and carbon steel Alloying Steels – with 5% non-carbon additions such as Mn, Cr, Ni, Cu, Si, Mo and V Stainless steel – more resistant to rusting due to Chromium addition (4%-30%) Tool steels – used for cutting, forming or shaping another material
Superalloys SUPERALLOYS - have been developed for high temperature service. Includes iron, cobalt and nickel-based materials A major application is in turbine materials, jet engines (both disc and blades)
Titanium Alloys TITANIUM - emerged as “wonder metal” in 1950 Relies on high strength/weight ratio, good resistance to corrosion, combined low thermal conductivity and thermal expansion Attractive for aerospace applications in both engine and airframe
Intermetallic Compounds are generally regarded as a class of materials between metals and ceramics Intrinsically strong with high elastic modulus Intermetallics containing Al or Si exhibit resistance to oxidation and corrosion Those made of light elements give rise to low density for weight-saving applications Greatest disadvantage is low ductility
Aluminum Alloys ALUMINUM - has an attractive combination of properties such as low density, strong and easy to fabricate. Its two most important properties are density and thermal conductivity In engines, they are used as pistons, cylinder heads and sumps However, modulus of aluminum is only one third that of steel Super plastic forming is a cost-effective manufacturing process for producing both simple and complex shapes from aluminum alloy sheets