DUCTILITY A ductile material bends twists and stretches
DUCTILITY • A ductile material bends, twists and stretches without fracture. A metal must be ductile to enable it to be drawn into wire 1
MALLEABILITY • The ability to withstand hammering and rolling without cracking. The malleability of most metals is increased by heating. 2
TOUGHNESS • The resistance to fracture or deformation under a blow or an impact. Toughness decreases with heat. 3
BRITTLENESS • Brittleness is the opposite to toughness. Brittle materials break easily with a sharp blow, are usually hard and are neither ductile nor malleable. Glass is an example of a brittle material. 4
CORROSION RESISTANCE • The ability to withstand chemical and electrochemical attack. Most materials break down in some way under chemical attack. Iron when exposed to oxygen and water will oxidise to rust (corrosion). 5
COLOUR • Besides being a means of distinguishing metals, colour is useful in decorative work. 6
FUSIBILITY • This is the property of becoming liquid when heated. Different metals have different melting points. 7
CONDUCTIVITY OF HEAT AND ELECTRICITY • This is the ability of a material to allow heat or electricity to flow through it. Silver and copper are the best conductors of both heat and electricity. 8
MAGNETIC PROPERTIES • Iron (and steel), nickel and cobalt are magnetic metals. Some steels become permanently magnetized but others lose their magnetism once removed from the magnetic field. These latter are used for electromagnets and transformer cores. 9
STRENGTH • This is the ability of a material to withstand forces of tension, compression and shear. 10
HARDNESS • The ability of a material to withstand scratching, indentation or wear. 11
ELASTICITY • The ability of a material to deform under load and return to its original shape when the load is removed. 12
PLASTICITY • This is the opposite to elasticity. This property enables a material to be permanently deformed, without fracture. A coin is made from a plastic material so that it will take the impression of the embossing tool. 13
- Slides: 13