7075 Aluminum Alloy Properties, AA 7075-T6, T7351, T651, Density, Composition

7075 aluminum alloy is one of the go-to materials when designers need an exceptional strength-to-weight ratio without jumping to steel or titanium. It is a high-strength, heat-treatable Al-Zn-Mg-Cu alloy used heavily in high-performance automotive and structural applications where pushing mass down while keeping strength up is the whole game.

Historically, 7075 has been around long enough to earn that reputation: it was developed in 1943 by Alcoa. Today, engineers and buyers still make the same core decisions when specifying it: confirm the chemical composition limits, use the right density for weight calculations, and choose the correct temper (such as T6, T651, or T7351) because temper selection directly affects strength, ductility, residual stress, and stress corrosion cracking behavior.

What 7075 Aluminum Alloy Is (and why it’s so strong)

AA 7075 is an aluminum-base alloy where zinc is the primary alloying element. In practice, it is often described as an Al-Zn-Mg-Cu alloy because zinc, magnesium, and copper are the core contributors to its high strength.

The reason 7075 stands out is not just “more alloying”; it is how the alloy is strengthened. Like other heat-treatable aluminum alloys, 7075 is strengthened primarily by precipitation hardening. That means the alloy is solution heat-treated, quenched, and aged so that strengthening particles precipitate out of solution in a controlled way. Zinc (Zn) plays a major role in enabling this precipitation-driven strengthening.

Where 7075 is typically used

7075 is widely selected for:

• Highly stressed structural components
• High-performance automotive parts where strength and fatigue resistance matter

The key selection tradeoff

7075’s “headline” strength comes with real-world corrosion and stress corrosion cracking (SCC) concerns. Temper selection (for example, T6 versus T7351) is one of the main tools engineers use to balance maximum strength against better SCC resistance.

Chemical Composition of 7075 (AA 7075): Range Limits and What Each Element Does

7075 composition table (weight percent; remainder Al)

Below is a practical composition limits table (percent by weight) commonly cited across datasheets and standards references (including ASTM B209M Table 1 as a commonly used reference point). Aluminum is the remainder.

Nominal examples cited in research literature include approximately 5.5% Zn, 2.5% Mg, and 1.5% Cu (Rajan et al.).

What each alloying element contributes (performance mapping)

7075’s performance is the outcome of a carefully balanced recipe. Here’s what the key elements do in practical engineering terms.

Zinc (Zn)

• Primary strengthening element in 7075
• Enables precipitation hardening and is a major reason for the alloy’s high strength

Magnesium (Mg)

• Contributes to strength and supports precipitation strengthening
• Cited as contributing to corrosion resistance in harsh environments (in the context of 7075’s alloying balance)

Copper (Cu)

• Increases strength and hardness
• Research notes that higher copper content is part of why 7075 can achieve a strong combination of strength, corrosion characteristics, and SCC resistance when paired with appropriate heat treatment

Chromium (Cr)

• Improves corrosion resistance and durability in extreme conditions
• Helps ductility and toughness by reducing crystal growth (microstructure control effect)

Impurities (Fe, Si, and others)

• Controlled by maximum caps to maintain consistency and target performance
• These maxima exist for a reason: uncontrolled impurities can push properties and manufacturability away from what designers expect

How composition is specified and verified (procurement reality)

In procurement and material certs, 7075 chemistry is typically expressed as percent by weight. For many product forms, buyers reference standards and published composition limits (ASTM B209M Table 1 is commonly cited for sheet and plate composition limits). Also note the practical nuance in some datasets: a combined Zr + Ti maximum of 0.25% may be used for extruded/forged products only by mutual supplier-purchaser agreement.

Density of 7075 Aluminum Alloy (and why published values vary)

Common density values (with unit callouts)

Most engineers use density both for weight estimates and to sanity-check stock dimensions versus mass. For 7075, you will see several “official-looking” numbers depending on the source and product context:

• 2.81 g/cc (same as 2.81 g/cm³) is widely reported
• 2,810 kg/m³ is also published (equivalent to 2.81 g/cm³)
• 0.102 lb/in³ is commonly cited
• Some sources list 0.101 lb/in³ (a small but real difference for large structures)
• Other published values include 2.80 Mg/m³ (equivalent to 2,800 kg/m³), 2.80 g/cm³, 2.85 g/cm³, and even 3.0 g/cm³ (makeitfrom.com)

A practical way to treat this is:

• For most quoting and early design: 2.81 g/cm³ (2,810 kg/m³; about 0.102 lb/in³)
• For tight weight budgets: use the density value specified by your governing material standard or supplier documentation, and keep it consistent across the bill of materials

Why density values vary in datasheets

Density variation between sources can come from:

• Rounding and unit conversion (g/cm³ to lb/in³ often introduces rounding differences)
• Product form differences (sheet, plate, bar, extrusions) and minor chemistry differences inside allowable limits
• Reference temperature and measurement method assumptions

Why density matters (context and comparison)

7075 is slightly denser than pure aluminum (as noted by Chalco Aluminum), because the alloying additions (especially Zn and Cu) increase mass per volume compared to nearly pure Al. Even with that slight increase, 7075 remains far lighter than steel and titanium, which is why it continues to dominate in high-performance and weight-sensitive structures.

Pros and Cons: Using 7075 for Real Parts

Frequently Asked Questions