aluSelect: Definition of Properties

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Definitions of Properties

Wrought Alloys

Corrosion & Anodizing

Physical & Elastic Properties

Formability, Machinability & weldability

Alloy Composition

Creep Properties

Fatigue Properties

Mechanical Properties

National/Company Alloy Designations

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Casting Alloys

Mechanical Properties

Physical & Surface Properties

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Temper Designations

Property definitions

Property		Definition		Units
Basic mechanical properties
Elongation A50		Permanent extension of the gauge length after fracture, expressed as a percentage of the original gauge length L₀ where L₀ is taken equal to 50 mm. Elongation is the simplest and most common representation of the ductility of the material.		%
Shear stress		Maximum gross stress (maximum force/original cross section) which the material withstands before fracture when submitted to a shear test. Applies typically to evaluate the resistance to fracture of rivets. Values are normally of the order of 0.6 R_m.		MPa
Ultimate tensile strength Rm		Tensile strength. Maximum gross stress (maximum force/original cross-section) which the material withstands before fracture during a tensile test.		MPa
Elongation A10		Elongation A10		%
Min elongation A5		Min elongation A5		%
Min elongation A50		Min elongation A50		%
Min ultimate tensile strength		Min ultimate tensile strength		MPa
Proof stress 0.2% Rp0.2		0.2% proof stress. Stress at which the material undergoes a 0.2% non-proportional (permanent) extension during a tensile test.		MPa
Min proof stress 0.2%		Min proof stress 0.2%		MPa
Elongation A5		Permanent extension of the gauge length after fracture, expressed as a percentage of the original gauge length L₀. where L₀ is taken equal to 5.65ÖS₀ and S₀ is the initial section of the test-piece. Elongation is the simplest and most common representation or the ductility of the material.		%
Cold formability properties
Suitability for spinning		Suitability for forming by pressing a circular metal blank or shell against a forming chuck with which it rotates, at high speed on a spinning lathe.		scale 2-7
Extrudability index		Extrudability index		scale 2-7
Cold formability index		General index in relation with the suitabitlty of the material for cold bending.		scale 2-7
Stretch formability index		Suitability for forming by stretching over a form block. Index closely related to the elongation at fracture of the material and to its strain hardening ability.		scale 2-7
Deep drawability index		Suitability for forming of deeply recessed parts by means of plastic deformation of the material.		scale 2-7
Corrosion properties
Rural atm corr index CORA		Rural atm corr index		scale 2-7
Exfoliation corrosion index, Al		Lamellar forn of corrosion, where the attack progresses in planes parallel to the surface resulting, with the accumulation of corrosion products, in a leafing effect in the product.		scale 2-7
Pitting corrosion index		Pitting corrosion index		scale 2-7
Pitting corrosion index		Localized corrosion resulting in small pits or craters in a metal surface.		scale 2-7
Exfoliation corrosion index EXCA		Exfoliation corrosion index		scale 2-7
Intercrystalline corrosion index		Corrosion occuring preferentially at grain boundaries.		scale 2-7
Marine atm corr index COMA		Marine atm corr index		scale 2-7
Industrial atm corr index COIA		Industrial atm corr index		scale 2-7
Corrosion index, general COA		Corrosion index, general		scale 2-7
Stress corrosion index		Failure by cracking resulting from selective directional attack caused by simultaneous interaction of sustained tensile stress of an exposed surface with the chemical or electrochemical effects of a service environment. Heat treated materials are generally more susceptible to this type of corrosion unless a specific precipitation treatment is carried out (T7 type tempers).		scale 2-7
Creep properties
Creep rupture strength Creep rupture strength		Maximum gross stress (maximum force/original cross-section) which the material withstands when submitted to sustained loading at elevated temperature. Long time exposures, up to 100000 hours, are generally requested. Creep rupture data are given for temperatures up to 300°C and exposure times up to 30 000 hours.		MPa
Elastic properties
Modulus of rigidity G		Shear or torsion modulus. Proportionality coefficient between stress and strain in pure shear. Derived from the Young's modulus using the relationship 2G= E/(1+n).		MPa
Modulus of elasticity E		Young's modulus. Proportionality coefficient between stress and strain for small deformation in uniaxial tensile testing (elastic range). s = E.dl/l where s is the uniaxial tensile stress in MPa and dl/l the strain in m/m.		MPa
Poisson's ratio n		Ratio between longitudinal elongation and transverse contraction in uniaxial testing. Taken equal to 0.33 for all alloys and tempers.
Fatigue properties
Min fatigue endurance limit		Min fatigue endurance limit		MPa
Fatigue strength		Resistance of a material to failure under cyclic loading. It is generally expressed as the stress range giving a 50% probability of fracture after a given number of load cycles. It is greatly influenced by the conditions of loading among which: R = stress ratio = minimum stress/maximum stress where tensile stresses are considered positive and compressive stresses negative: For example R = -1 for rotary bending. Kt = stress intensity factor = expression of the stress concentration associated with a stress raiser such as a notch. Kt = 1 for a flat surface. Stress range = algebraic difference between maximum and minimum stress over one cycle where tensile stresses are considered positive and compressive stresses negative. Test method. Rotary bending, uniaxial stressing (push-pull), planar bending, etc. Fracture strength values also depend on the probability of fracture under consideration (5%. 50% or 95%). Caution All fatigue strength values in ALUSELECT are expressed as stress ranges. For example a rotary bending test with a maximum applied stress of 120 MPa will be represented by a stress range of 240 MPa since the stress will fluctuate between +120 MPa and -120 MPa over one cycle.		MPa
Fatigue endurance limit		Stress range giving a 50% probability of rupture, in rotary bending, after 10⁸ cycles.		MPa
Hardness properties
Hardness, Brinell HB		Brinell hardness. Resistance to penetration of a spherical indentor under standardized conditions. Approximately equal to 0.3 R_m when R_m is expressed in MPa. In addition to providing a simple method for assessing material strength, hardness is also related to the wear resistance of the material.		HB
Hardness, Vickers HV		Vickers hardness. Resistance to penetration of a square-based pyramidal diamond indentor under standardized conditions. Approximately equal to 1.10 HB. In addition to providing a sample method for assessing material strength, hardness is also related to the wear resistance of the material.		HV
Min hardness, Brinell HBN		Min hardness, Brinell		HBN
Joining properties
Shielded arc weldability index		Suitability for fusion welding using an arc produced between an electrode and the parts to be welded. An inert gas or gas mixture shields the arc and the weld puddle.		scale 2-7
Spot & seam weldability index		Suitability for fusion welding by passing a current between two electrodes which clamp the parts to be welded.		scale 2-7
Electron beam weldability index		Suitability for fusion welding by submission to a stream of high energy electrons.		scale 2-7
Solderability index		Suitabillty for joining at a temperature below the solidus temperature of the part using a fliter metal with a liquidus temperature below 425°C.		scale 2-7
Brazability index		Suitability for joining at a temperature below the solidus temperature of the part using a filler metal with a liquidus temperature above 425°C		scale 2-7
Oxy-gas weldability index		Suitability for fusion welding by submission to a flame from an oxygen and gas mixture.		scale 2-7
Machinability properties
Machinability index		Characterizes the ease of chip fragmentation during milling.		scale 2-7
Physical properties
Coefficient of thermal expansion a		Expansion per unit length when the material temperature is raised one degree. It is expressed in µm per m and per K. This coefficient depends on the actual temperature. It decreases at lower temperatures. The values given are average values for the temperature range 0 to 100°C.		µm m^-1 K^-1
Resistivity r_el		r_el coefficient in Ohm's law E = r_el.I, where E is the electric field and I the current density. It increases with increasing temperature. Values given are for room temperature.		nW m
Liquidus temperature T_liq		Temperature at which total melting of the solid is achieved upon heating from the solid state, or at which solid first appears upon cooling from the liquid state.		°C
Solidus temperature T_sol		Temperature at which liquid first appears upon heating from the solid state. For some alloys prior homogenizing may significantly raise the solidus temperature (AA7075 for example). Exceeding the solidus temperature during heat-treating has extremely deleterious effect on material properties.		°C
Melting point		Melting point		°C
Density r		Mass per unit volume		kg m^-3
Thermal conductivity l		l coefficient in Fourier's law F = l dT/dx where F is the heat flux per unit area (in W m^-2) and dT/dx the temperature gradient (in K per m). Decreases with increasing temperature. Values given are for room temperature (generally derived from electrical conductivity values using Lorentz's law).		W m^-1 K^-1
Electrical conductivity EC		Reciprocal of the electrical resistivity. It decreases with increasing temperature. Values given are for room temperature. Values are expressed as percent %IACS (International Annealed Copper Standard) which allows direct comparison with copper. Values in MS/m can be readily obtained by applying a conversion factor of 0.58. For example 40% IASC is equivalent to 23.2 MS/m. Conversion from conductivity to resistivity is also readily achieved. For example 23.2 MS/m is equivalent to 1/23.2 µWm = 43 nWm.		%IACS
Specific heat capacity C_p		Amount of heat (expressed in Joules) necessary to raise the temperature of 1 kg of material by 1K, ander constant pressure. C_p increases with temperature. The values are given at room temperature.		J kg^-1 K^-1
Surface treatment properties
Bright anodising index ANBA		Anodizing with brightness as the primary objective.		scale 2-7
Colour anodising index ANCA		Incorporation of colouring matter, either during anodizing or by subsequent processing, into the film of anodized aluminium.		scale 2-7
Hard anodising index ANHA		Anodizing under special conditions to produce a hard film offering extremely high resistance to abrasion.		scale 2-7
Protective anodising index ANPA		Anodizing where protection against corrosion or wear is the primary objective and appearance is of secondary or no importance.		scale 2-7
Cast mechanical properties
Hot tear resistance		Ability to withstand 'tearing' at higher temperatures. The test is performed by placing stress on an area of the material where a flaw is located.		scale 2-7
Pressure tightness		The ability of a cast product to withstand high pressure (absence of leakage or interconnected porosity).		scale 2-7
Cast physical properties
Fluidity		The ability of a molten metal or alloy to flow, i.e. into a mould during casting.		scale 2-7