Properties of materials Mechanical properties of materials Strength, Toughness, Hardness, Ductility, Elasticity, Fatigue and Creep Chemical properties Oxidation, Corrosion, Flammability, Toxicity, … Physical properties Density, Specific heat, Melting and boiling point, Thermal expansion and conductivity, Electrical and magnetic properties
Material Specification Chemical composition Mechanical properties – Strength, hardness (under various conditions: temperature, humidity, pressure) Physical properties – density, optical, electrical, magnetic Environmental – green, recycling
Metals Ferrous Metals –Cast irons –Steels Super alloys –Iron-based –Nickel-based –Cobalt-based Non-ferrous metals –Aluminum and its alloys –Copper and its alloys –Magnesium and its alloys –Nickel and its alloys –Titanium and its alloys –Zinc and its alloys –Lead & Tin –Refractory metals –Precious metals
General Properties and Applications of Ferrous Alloys Ferrous alloys are useful metals in terms of mechanical, physical and chemical properties. Alloys contain iron as their base metal. Carbon steels are least expensive of all metals while stainless steels is costly.
Carbon and alloy steels Carbon steels Classified as low, medium and high: 1.Low-carbon steel or mild steel, < 0.3%C, bolts, nuts and sheet plates. 2.Medium-carbon steel, 0.3% ~ 0.6%C, machinery, automotive and agricultural equipment. 3.High-carbon steel, > 0.60% C, springs, cutlery, cable.
Carbon and alloy steels Alloy steels Steels containing significant amounts of alloying elements. Structural-grade alloy steels used for construction industries due to high strength. Other alloy steels are used for its strength, hardness, resistance to creep and fatigue, and toughness. It may heat treated to obtain the desired properties.
Carbon and alloy steels High-strength low-alloy steels Improved strength-to-weight ratio. Used in automobile bodies to reduce weight and in agricultural equipment. Some examples are: 1.Dual-phase steels 2.Micro alloyed steels 3.Nano-alloyed steels
Stainless steels Characterized by their corrosion resistance, high strength and ductility, and high chromium content. Stainless as a film of chromium oxide protects the metal from corrosion.
Stainless steels Five types of stainless steels: 1.Austenitic steels 2.Ferritic steels 3.Martensitic steels 4.Precipitation-hardening (PH) steels 5.Duplex-structure steels
Typical Selection of Carbon and Alloy Steels for Various Applications
Mechanical Properties of Selected Carbon and Alloy Steels in Various Conditions
AISI Designation for High-Strength Sheet Steel
Room-Temperature Mechanical Properties and Applications of Annealed Stainless Steels
Tool and die steels Designed for high strength, impact toughness, and wear resistance at a range of temperatures.
Basic Types of Tool and Die Steels
Processing and Service Characteristics of Common Tool and Die Steels
Aluminium and aluminium alloys Factors for selecting are: 1.High strength to weight ratio 2.Resistance to corrosion 3.High thermal and electrical conductivity 4.Ease of machinability 5.Non-magnetic
Magnesium and magnesium alloys Magnesium (Mg) is the lightest metal. Alloys are used in structural and non- structural applications. Typical uses of magnesium alloys are aircraft and missile components. Also has good vibration-damping characteristics.
Copper and copper alloys Copper alloys have electrical and mechanical properties, corrosion resistance, thermal conductivity and wear resistance. Applications are electronic components, springs and heat exchangers. Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin.
Nickel and nickel alloys Nickel (Ni) has strength, toughness, and corrosion resistance to metals. Used in stainless steels and nickel-base alloys. Alloys are used for high temperature applications, such as jet-engine components and rockets.
Superalloys Superalloys are high-temperature alloys use in jet engines, gas turbines and reciprocating engines.
Titanium and titanium alloys Titanium (Ti) is expensive, has high strength- to-weight ratio and corrosion resistance. Used as components for aircrafts, jet-engines, racing-cars and marine crafts.
Refractory metals Refractory metals have a high melting point and retain their strength at elevated temperatures. Applications are electronics, nuclear power and chemical industries. Molybdenum, columbium, tungsten, and tantalum are referred to as refractory metal.
Other nonferrous metals 1.Beryllium 2.Zirconium 3.Low-melting-point metals: - Lead - Zinc - Tin 4.Precious metals: - Gold - Silver - Platinum
Special metals and alloys 1.Shape-memory alloys (i.e. eyeglass frame, helical spring) 2.Amorphous alloys (Metallic Glass) 3.Nanomaterials 4.Metal foams
Heat Treatment of Metals Annealing –Full annealing –Normalising (faster rate of cooling) –Recovery annealing (longer holding time, slower rate of cooling,) –Stress relieving (lower temperature) Martensite formation in steel –Austenitizing (conversion to austenite) –Quenching (control cooling rate –Tempering (reduce brittleness)
Furnaces for Heat Treatment Fuel fire furnaces –gas –oil Electric furnaces –batch furnaces box furnaces - door car-bottom furnaces - track for moving large parts bell-type furnaces - cover/bell lifted by gantry crane –continuous furnaces
Furnaces for Heat Treatment Vacuum furnaces Salt-bath furnaces Fluidized-bed furnaces Some of the furnaces have special atmosphere requirements, such as carbon- and nitrogen- rich atmosphere.
Classification of Polymers –Thermoplastics –Thermosets –Elastomers
Polymers Thermoplastics - reversible in phase by heating and cooling. Solid phase at room temperature and liquid phase at elevated temperature. Thermosets - irreversible in phase by heating and cooling. Change to liquid phase when heated, then follow with an irreversible exothermic chemical reaction. Remain in solid phase subsequently. Elastomers - Rubbers
Composite Materials Metal Matrix Composites (MMC) Mixture of ceramics and metals reinforced by strong, high-stiffness fibers Ceramic Matrix Composites (CMC) Ceramics such as aluminum oxide and silicon carbide embedded with fibers for improved properties, especially high temperature applications. Polymer Matrix Composites (PMC) Thermosets or thermoplastics mixed with fiber reinforcement or powder.
Composite Materials 1D fibre Woven fabric Random fibre
Taxonomy of Materials Selection Ashby,: Material Selection in Mechanical Design