Aluminium Alloy - Austral Wright Metals

Product Data Sheet – Aluminium Alloys

Aluminium 5251  UNS-A95251

Aluminium alloy 5251 contains nominally 2.0% magnesium & 0.30% manganese. It has good workability, medium static strength, high fatigue strength, good weldability, and very good corrosion resistance, especially in marine atmospheres. It also has the low density and excellent thermal conductivity common to all aluminium alloys. It is commonly used in sheet, plate and tube form.

Typical Applications Architecture, general sheet metal work, small boats.

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Chemical Composition

Aluminium Development Council of Australia

Element %
Aluminium
Balance
Mangnesium
1.7 – 2.4
Manganese
0.10 – 0.50
Chromium
0.15 max
Copper
0.15 max
Iron 0.50 max
Element %
Silicon
0.40 max
Titanium
0.15 max
Zinc
0.15 max
Others (each)
0.05 max
Others (total)
0.15 max

 

 

Mechanical Properties

Aluminium Development Council of Australia

Temper 0.2% Proof Stress, MPa min Tensile Strength, MPa Elongation % min
O (annealed) 65 170 – 215 15 – 20
H32 130 200 – 255 4 – 11
H34 180 230 – 275 3 – 8
H36 210 250 – 295 3 – 4
H38 225 260 min 3 – 4

† For information only, proof stress is not specified or measured except by prior agreement

‡ Minimum elongation, actual value depends on thickness – thicker gauges have higher elongation

 

 

Key To Tempers

Temper
Condition
O
Annealed (soft)
H1x
Strain hardened only
H3x
Strain hardened and then stabilised (ie. low temperature heat treated to pre-empt natural ageing, by reducing strength and increasing ductility)
Second digit: (x)
8
full hard
4
½ hard
6
¾ hard
2
¼ hard

 

 

Description Aluminium 5251 is an aluminium magnesium manganese alloy which can be hardened by cold work: it is not heat treatable to higher strength. It is about mid way through the series of aluminium magnesium alloys for alloying content and strength, which is very similar to alloy 5052.

Austral Wright Metals can supply this alloy as plate, sheet and strip. See Austral Wright Metals Catalogue for normal stock sizes and tempers.

Corrosion Resistance 5251 has the same high resistance to general corrosion as other non heat treatable aluminium alloys. It also has the higher resistance to slightly alkaline conditions common to the 5000 series alloys. The resistance of 5251 to corrosion in marine atmospheres is excellent, exceeding that of 5005, hence the frequent use of 5251 in marine applications such as small boats and dinghies.

The corrosion resistance of aluminium alloys relies on a protective surface oxide film, which when damaged is readily repaired by the rapid reaction between aluminium and oxygen. However, the high reactivity of the base metal can give rapid corrosion if the film cannot be repaired, so aluminium alloys are not suitable for use with reducing media. 5251 can be anodised to improve the corrosion resistance by thickening the protective surface film.

Since aluminium is a reactive metal, it may corrode more quickly when in electrical contact with most other metals. The prediction of galvanic corrosion is complex; please consult Austral Wright Metals for specific advice.

Pressure Vessels AS1210 Pressure Vessels and AS4041 Pressure Piping prequalify the alloy for pressure service for temperatures up to 200°C.

Physical Properties

Property
At
Value
unit
Density
20°C
2,680
kg/m³
Melting Range
607 – 650
°C
Modulus of Elasticity
Tension
20°C
69.3
GPa
Torsion
20°C
25.9
GPa
Compression
20°C
70.7
GPa
Mean Coefficient of Expansion
20°C
23.75
x 10 -6 / °C
Thermal Conductivity
25°C
138
W / m. °C
Electrical Resistivity
20°C
0.050
micro-ohm . m
Electrical Conductivity
Equal Volume
20°C
35
% IACS
Equal Weight
20°C
116
% IACS

 

Fabrication Aluminium 5251 is not generally hot worked. It is very readily cold formable in the annealed condition, as it is ductile. Forming loads and tool & press wear are generally less than with carbon steel. For piercing and blanking the punch to die clearance should be about 7% of the thickness per side for the H32 & H34 tempers. Sharp tools are required.

 

Indicative Minimum Bend Radii

for 90° cold forming for various thickness, t mm

t = thickness

Temper
0.4 0.8 1.6 3.2 4.8 6.4 9.5 13
H32
0 t
0 t
1 t
1½t
1½t
1½t 1½t 2 t
H34
0 t
1 t
1½ t
2t
2 t
2½t 2½t 3 t

 

Machinability 5251 is readily machinable by conventional methods. It should be machined at high speed with copious lubrication to avoid thermal distortion of the workpiece. Sharp tools are essential. High speed steel or tungsten carbide may be used. Cuts should be deep and continuous, with high cutting speeds. Woodworking machinery may be suitable for short runs.
Welding 5251 is readily weldable by standard techniques. It is frequently welded with GTAW (TIG) or GMAW (MIG). Aluminium must be very dry & clean to avoid contamination & porosity of the weld. Filler metals 1100, 4043 or 4047 are used. 4043 is the most crack tolerant. Shielding gas must be dry & free of hydrogen.

Heat Treatment Aluminium 5251 is annealed at 345°C, time at temperature and cooling rate are unimportant. Stress relief is rarely required, but can be carried out at about 220°C. If loss of strength is of concern, stress relief tests should be conducted.

 

ASTM Product Specifications

Specification
Title
B209
Aluminium and Aluminium Alloy Sheet and Plate
B316
Aluminium and Aluminium Alloy Rivet & Cold Heading Wire & Rods
B210
Aluminium and Aluminium Alloy Drawn Seamless Tubes
B483
Aluminium and Aluminium Alloy Drawn Tubes for General Purpose Applications

 

Typical Strength of Alloys

 5005 & 5251 in the H32 & H34 tempers

Typical Strength of Aluminium Alloys - 5251 strength

Grade 5251 has equivalent ductility to 5052

 

 

The technical advice and recommendations made in this Product Data Sheet should not be relied or acted upon without conducting your own further investigations, including corrosion exposure tests where needed. Please consult current editions of standards for design properties. Austral Wright Metals assumes no liability in connection with the information in this Product Data Sheet. Austral Wright Metals supplies a comprehensive range of stainless steels, copper alloys, nickel alloys and other high performance metals for challenging service conditions. Our engineers and metallurgists will be pleased to provide further data and applications advice.

 

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