Properties of Metals

The various properties of metals can be assessed by accurate laboratory tests on sample pieces. The following are the terminologies that are associated with these properties.

• Brittleness: It is the tendency of the metal to shatter without significant deformation. It will shatter under a sudden low stress, but will resist a slowly-applied, higher load.
• Conductivity: It is the ability of a metal to conduct heat and electricity. Silver and copper are excellent thermal and electrical conductors.
• Ductility: It is the property of being able to be permanently extended by a tensile force. It is measured during a tensile or stretching test, when the amount of stretch (elongation) for a given applied load, provides an indication of a metal’s ductility.
• Elasticity: It is the ability of a metal to return to its original shape and size after the removal of any distorting force. The ‘Elastic Limit’ is the greatest force that can be applied without permanent distortion.
• Hardness: It is the ability of a metal to resist wear and penetration and is measured by pressing a hardened steel ball or diamond point into the metal’s surface. The diameter or depth of the resulting indentation provides an indication of the metal’s hardness.
• Malleability: It is the ease with which the metal can be forged, rolled and extruded without fracture. Stresses induced into the metal, by the forming processes, have to be subsequently relieved by heat-treatment. Hot metal is more malleable than cool metal.
• Plasticity: It is the ability to retain a deformation after the load producing it has been removed. In fact, plasticity is the opposite of elasticity.
• Tenacity: It is the property of a metal to resist deformation when subjected to a tensile load. It is proportional to the maximum stress required to cause the metal to fracture.
• Toughness: It is the ability of a metal to resist suddenly applied loads. A metal’s toughness is tested by impact with a swinging pendulum of known mass.
• Strength: There are several different measurements of the strength of a metal, as may be seen from the following sub-paragraphs.

• Tensile Strength: It is the ability to resist tension forces applied to the metal.
• Yield Strength: It is the ability to resist deformation. After the metal yields, it is said to have passed its yield point.
• Shear Strength: It is the ability to resist side-cutting loads, such as those imposed on the shank of a rivet, when the materials it is joining attempt to move apart in a direction normal to the longitudinal axis of the rivet.
• Bearing Strength: It is the ability of a metal to withstand a crushing force.