Aluminium - general notes
Availability
Aluminium is the most common metallic element and its oxide form, known as bauxite, is the third most abundant substance.
Bi-metallic Corrosion
In the presence of moisture direct contact between aluminium and other metals should be avoided otherwise bi-metallic corrosion may occur. Where there is such
potential for bi-metallic corrosion then the different metals must be isolated from each other by means of a suitable gasket or by coating or painting the contact area. There is no risk of bi-metallic corrosion in dry conditions.
Corrosion resistance
Aluminium is highly resistant to weathering, even in polluted industrial atmospheres and also resists attack from many acids.
The excellent corrosion resistance of aluminium is due to the permanent presence on the surface of an invisible oxide film, making the material environmentally passive. If the surface is cut or scratched the protective film immediately reforms. Unless some substance or condition destroys this oxide coating, the metal remains resistant to corrosion.
Fabrication
The working qualities of aluminium make for ease of fabrication. Its forming and handling characteristics are among its most important advantages. Favourable
comparisons can often be made with less expensive materials as its lower degree of workability results in reduced processing costs.
Fire
Aluminium does not burn in the form of sheets, extrusions, castings, foil, etc. Even the thinnest gauge material will not burn or support combustion.
The thermal conductivity of aluminium is around four times that of steel, and its specific heat twice that of steel. Heat is therefore conducted away faster, and a greater heat input necessary to bring aluminium to a given temperature than with steel.
As defined by BS476:Part 4 aluminium alloys are non-combustible and provide Class 1 surface spread of flame to BS476:Part 5.
Joining flexibility
As with all other common metals, aluminium lends itself to the primary joining techniques including bolting, bonding, brazing, screwing, riveting, and welding.
Lightness
Aluminium is the lightest of all common metals with a specific gravity of 2.7, being approximately one third that of steel.
The excellent strength to weight ratio of aluminium delivers substantial weight saving benefits of up to 50% when compared with equivalent steel assemblies. Significant cost savings are also achieved in terms of transportation (fuel economy) and easier / faster handling and fixing (fewer personnel).
Machinability
Most alloy grades can be easily and economically machined. Aluminium alloy can be milled, turned, etc. at relatively high speeds resulting in faster production times and lower part prices.
Reflection of radiant energy
Aluminium is an excellent reflector of light and heat. About 75% of light and 90% of heat are reflected, making it widely used for lighting fixtures, decorative trims, and insulating applications.
Recycling
Aluminium has the advantage of a high scrap value and is therefore economic to recycle into reusable high-grade metal. Recycling aluminium needs only 5% of the energy required to extract from bauxite ore. Today the use of reprocessed aluminium accounts for 30% of the production of the primary metal. This process can be continually repeated.
Temperature (effects of)
Temperatures typically encountered within normal living environments do not effect the performance of aluminium or aluminium alloys.
Strength
Commercially pure aluminium (99.5%) produced in temper hardened condition has a useful degree of hardness and excellent forming qualities. Substantial increases in metal strength are obtained by alloying aluminium with small percentages of other metals including copper, manganese, magnesium, silicon and zinc.
Many alloys can also be heat treated to further increase strength.
Aluminium is the most common metallic element and its oxide form, known as bauxite, is the third most abundant substance.
Bi-metallic Corrosion
In the presence of moisture direct contact between aluminium and other metals should be avoided otherwise bi-metallic corrosion may occur. Where there is such
potential for bi-metallic corrosion then the different metals must be isolated from each other by means of a suitable gasket or by coating or painting the contact area. There is no risk of bi-metallic corrosion in dry conditions.
Corrosion resistance
Aluminium is highly resistant to weathering, even in polluted industrial atmospheres and also resists attack from many acids.
The excellent corrosion resistance of aluminium is due to the permanent presence on the surface of an invisible oxide film, making the material environmentally passive. If the surface is cut or scratched the protective film immediately reforms. Unless some substance or condition destroys this oxide coating, the metal remains resistant to corrosion.
Fabrication
The working qualities of aluminium make for ease of fabrication. Its forming and handling characteristics are among its most important advantages. Favourable
comparisons can often be made with less expensive materials as its lower degree of workability results in reduced processing costs.
Fire
Aluminium does not burn in the form of sheets, extrusions, castings, foil, etc. Even the thinnest gauge material will not burn or support combustion.
The thermal conductivity of aluminium is around four times that of steel, and its specific heat twice that of steel. Heat is therefore conducted away faster, and a greater heat input necessary to bring aluminium to a given temperature than with steel.
As defined by BS476:Part 4 aluminium alloys are non-combustible and provide Class 1 surface spread of flame to BS476:Part 5.
Joining flexibility
As with all other common metals, aluminium lends itself to the primary joining techniques including bolting, bonding, brazing, screwing, riveting, and welding.
Lightness
Aluminium is the lightest of all common metals with a specific gravity of 2.7, being approximately one third that of steel.
The excellent strength to weight ratio of aluminium delivers substantial weight saving benefits of up to 50% when compared with equivalent steel assemblies. Significant cost savings are also achieved in terms of transportation (fuel economy) and easier / faster handling and fixing (fewer personnel).
Machinability
Most alloy grades can be easily and economically machined. Aluminium alloy can be milled, turned, etc. at relatively high speeds resulting in faster production times and lower part prices.
Reflection of radiant energy
Aluminium is an excellent reflector of light and heat. About 75% of light and 90% of heat are reflected, making it widely used for lighting fixtures, decorative trims, and insulating applications.
Recycling
Aluminium has the advantage of a high scrap value and is therefore economic to recycle into reusable high-grade metal. Recycling aluminium needs only 5% of the energy required to extract from bauxite ore. Today the use of reprocessed aluminium accounts for 30% of the production of the primary metal. This process can be continually repeated.
Temperature (effects of)
Temperatures typically encountered within normal living environments do not effect the performance of aluminium or aluminium alloys.
Strength
Commercially pure aluminium (99.5%) produced in temper hardened condition has a useful degree of hardness and excellent forming qualities. Substantial increases in metal strength are obtained by alloying aluminium with small percentages of other metals including copper, manganese, magnesium, silicon and zinc.
Many alloys can also be heat treated to further increase strength.
Aluminium Grade 6063
Aluminium alloy 6063 is a medium strength alloy commonly referred to as an architectural alloy. It is normally used in intricate extrusions.
It has a good surface finish, high corrosion resistance, is readily suited to welding and can be easily anodised.
Most commonly available as T6 temper, in the T4 condition it has good formability
Aluminium alloy 6063A is a variation of 6063 with greater strength but retains the same good surface finish qualities and affinity for anodising
The most common temper for 6063 aluminium are:
O - Soft
T4 - Solution heat treated and naturaly aged to a substantially stable condition
T6 - Solution heat treated and artificially aged
Physical Properties:
Density 2.70 Kg/m³
Melting Point 600 °C
Thermal Expansion 23.5 x10-6/K
Modulus of Elasticity 69.5 GPa
Thermal Conductivity 200 W/m.K
Electrical Resistivity 0.035 x10-6Ω.m
Mechanical properties (T6)
Proof Stress 160 Min MPa
Tensile Strength 195 Min MPa
Elongation 14 %
Shear Strength 150 MPa
Hardness Vickers 80 HV
Welding:
6063 is suitable for all conventional welding methods. Welding wire generally should be alloy 5183 or alloy 4043. When maximum electrical conductivity is required use alloy 4043. For strength and conductivity use alloy 5346 and increase the size of the weld to compensate for the lower conductivity.
It has a good surface finish, high corrosion resistance, is readily suited to welding and can be easily anodised.
Most commonly available as T6 temper, in the T4 condition it has good formability
Aluminium alloy 6063A is a variation of 6063 with greater strength but retains the same good surface finish qualities and affinity for anodising
The most common temper for 6063 aluminium are:
O - Soft
T4 - Solution heat treated and naturaly aged to a substantially stable condition
T6 - Solution heat treated and artificially aged
Physical Properties:
Density 2.70 Kg/m³
Melting Point 600 °C
Thermal Expansion 23.5 x10-6/K
Modulus of Elasticity 69.5 GPa
Thermal Conductivity 200 W/m.K
Electrical Resistivity 0.035 x10-6Ω.m
Mechanical properties (T6)
Proof Stress 160 Min MPa
Tensile Strength 195 Min MPa
Elongation 14 %
Shear Strength 150 MPa
Hardness Vickers 80 HV
Welding:
6063 is suitable for all conventional welding methods. Welding wire generally should be alloy 5183 or alloy 4043. When maximum electrical conductivity is required use alloy 4043. For strength and conductivity use alloy 5346 and increase the size of the weld to compensate for the lower conductivity.
Aluminium Grade 6061
Aluminium alloy 6061 is a medium to high strength heat-treatable alloy with a strength higher than 6005A. It has very good corrosion resistance and very good weldability although reduced strength in the weld zone. It has medium fatigue strength. It has good cold
formability in the temper T4, but limited formability in T6 temper. Not suitable for very complex cross sections.
The most common temper for 6061 aluminium is:
T6 - Solution heat treated and artificially aged
Physical Properties:
Density 2.70 Kg/m³
Melting Point 650 °C
Thermal Expansion 23.4 x10-6 /K
Modulus of Elasticity 70 GPa
Thermal Conductivity 166 W/m.K
Electrical Resistivity 0.040 x10-6 Ω .m
Mechanical Properties:
Proof Stress 270 MPa
Tensile Strength 310 MPa
Elongation 12 %
Shear Strength 190 MPa
Hardness Vickers 100 HV
The most common temper for 6061 aluminium is:
T6 - Solution heat treated and artificially aged
Physical Properties:
Density 2.70 Kg/m³
Melting Point 650 °C
Thermal Expansion 23.4 x10-6 /K
Modulus of Elasticity 70 GPa
Thermal Conductivity 166 W/m.K
Electrical Resistivity 0.040 x10-6 Ω .m
Mechanical Properties:
Proof Stress 270 MPa
Tensile Strength 310 MPa
Elongation 12 %
Shear Strength 190 MPa
Hardness Vickers 100 HV