Density of aluminium alloys by series, and how much weight you save over steel

How dense is aluminium compared with steel and titanium?

Aluminium alloys at 2.64 to 2.84 g/cm³ are about 2.9 times lighter than ASTM A36 structural carbon steel (UNS K02600) at 7.80 g/cm³ (Wikipedia) and about 1.6 times lighter than titanium alloy Ti-6Al-4V (Grade 5) (UNS R56400, EN 3.7165) at 4.43 g/cm³ (Boze material guide), taking aluminium alloy 6061 at 2.70 g/cm³. Choosing a metal family moves weight far more than choosing an aluminium series.

What does the density mean for a real part?

Mass equals volume times density. A 10 kg part in ASTM A36 structural carbon steel (UNS K02600) becomes about 3.46 kg in aluminium alloy 6061, but aluminium alloys are also less stiff: the elastic modulus of A36 is 2.9 times that of 6061, so a part of the same shape flexes more. Pick the alloy series for strength, corrosion and forming, because weight differs by under 8% between series.

Does the alloy series matter for weight?

Hardly. Moving a 10 kg part from aluminium alloy 5019 at 2.64 g/cm³ (no temper or form stated; Bikar) to aluminium alloy 2219 at 2.84 g/cm³ (infobox value; the page gives no temper or test temperature; Wikipedia) adds 0.8 kg. Pick the series for the job (strength, corrosion, welding, forming) and treat the weight difference as small.

Can you swap steel for aluminium one for one?

Not without a check. The same volume gives a part about 2.9 times lighter, but aluminium is also less stiff, and its strength depends on alloy and temper. As general engineering knowledge, not in our data, a part of the same shape deflects roughly in proportion to one over the elastic modulus, so the 6061 version flexes about 2.9 times more under the same load.

Yield values mix typical and minimum figures, tempers and product forms, so compare them only as a rough guide; the conditions are on each profile. For strength per kilogram, which is the fair test, read strongest lightweight metals.

How much does a given amount of aluminium weigh?

Weight is volume times density, so the stock sizes below follow straight from the records. Multiply the sheet figure by the thickness in millimetres.

What data is missing or uncertain?

Not found in any source we hold: a density for cast aluminium alloys, which have no profile in the Space Mushroom database. Series 4xxx and 8xxx rest on one alloy each, 3 alloys are converted from pounds per cubic inch, and 10 of 28 alloys have sources that disagree. Most records state no temper or temperature. The list below gives the detail.

• Cast alloys are missing. Not found in any source we hold. The atlas covers wrought alloys, fillers and foil only.
• Several series rest on few alloys. 1xxx has 2, 2xxx has 9, 3xxx has 2, 4xxx has 1, 5xxx has 6, 6xxx has 5, 7xxx has 2, 8xxx has 1. The series ranges are the spread of those alloys, not of every alloy in the series.
• Most records do not state temper, form or temperature. Where they do, the profile gives it (see the records under each card). Density changes slightly with temperature (general engineering knowledge, not in our data); where a record gives a temperature it is 20 °C or ambient, and most give none.
• 3 alloys come from pounds per cubic inch. 2195, 4047, 6101 are converted and carry the † mark; the unit change is exact but the sources print only two or three digits.
• 2017 and 2017A share one source page (Referans Metal), so they are not two independent checks.
• One record is left out on purpose. The aluminium-magnesium 5XXX series profile also holds a density of 2.76 g/cm³ for a recycled Al-Mg-Ni rod, which the profile says is not a standard 5xxx grade.
• Aluminium bronze is not an aluminium alloy. It is a copper alloy, and the aluminium bronze profile records 7.58 g/cm³ (Aalco), nearly as dense as steel. Do not use the aluminium numbers for it.

Where do sources disagree on density?

For 10 of the 28 profiles, two sources print different values. We show every record under each card and use the full range for the series, so both numbers appear.

Questions people ask about the density of aluminium