Aluminum EN AW-7020: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

EN AW-7020 is a 7xxx-series aluminum alloy primarily strengthened by Zn-Mg additions and limited Cu content. It is commonly identified in standards as AlZn4.5Mg1, placing it among the heat-treatable, high-strength Al-Zn-Mg family with controlled impurity levels for improved toughness and corrosion resistance.

The major alloying elements are zinc (primary), magnesium, and trace copper with small additions of manganese, iron, chromium and titanium. Strengthening is achieved via precipitation hardening after solution treatment and artificial aging, although limited work-hardening can be combined for specific tempers such as T651 for residual stress relief.

Key traits include high specific strength, competitive fatigue resistance, and relatively good atmospheric corrosion behaviour for a 7xxx-series alloy due to lower Cu content. Weldability and formability are moderate: the alloy can be formed in softer tempers and welded with appropriate filler and post-weld treatment, but heat-affected zone softening and SCC susceptibility require attention.

Typical industries using EN AW-7020 are aerospace structural fittings, high-performance automotive components, railway and marine structural parts, and extrusion-based architectural elements. Engineers choose EN AW-7020 when a balance of elevated strength, decent corrosion resistance, and good extrudability is required, especially where 7075’s higher strength is unnecessary or where 6000-series alloys lack sufficient strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; best formability and machinability, lowest strength
H14	Medium	Medium-Low	Good	Good	Strain-hardened, partial springback control; limited use for thin sheet
T5	Medium-High	Medium	Fair	Fair	Cooled from hot working and artificially aged; good dimensional stability
T6	High	Low-Medium	Fair	Fair-Poor	Solution-treated and artificially aged; peak strength for many applications
T651	High	Low-Medium	Fair	Fair-Poor	T6 + stress relief by stretching; reduced residual stresses for critical parts

Tempers control the balance between strength, ductility and formability by adjusting microstructure and dislocation density. Soft tempers such as O maximize ductility and allow severe forming operations, while T6/T651 provide peak performance at the expense of elongation and ease of cold forming.

Chemical Composition

Element	% Range	Notes
Si	≤0.3	Controlled impurity; excessive Si may form intermetallics that reduce toughness
Fe	≤0.5	Typical impurity; higher Fe increases brittleness and reduces ductility
Mn	0.05–0.5	Improves grain structure control and fracture toughness in small amounts
Mg	0.8–1.3	Combines with Zn to form strengthening precipitates (MgZn2) during aging
Cu	0.05–0.4	Kept low compared with 7075 to improve corrosion resistance; contributes to strength
Zn	3.5–5.0	Primary strength alloying element; governs precipitation hardening response
Cr	0.05–0.25	Grain boundary control and recrystallisation inhibitor; helps toughness
Ti	≤0.15	Grain refiner for cast and wrought products; small additions aid microstructure
Others (Al balance)	Balance	Aluminum matrix + trace impurities; balance is remainder to 100%

The Zn–Mg combination promotes formation of fine metastable MgZn2 precipitates during artificial aging, producing high tensile and yield strengths. Minor elements like Cr and Mn act as grain refiners and recrystallization inhibitors, which improve toughness and fatigue resistance, while controlled Cu levels are used to limit SCC and improve atmospheric durability.

Mechanical Properties

EN AW-7020 exhibits a distinct change in tensile and yield properties between annealed and peak-aged conditions, reflecting its heat-treatable nature. In annealed (O) condition, the alloy shows modest tensile strength and high elongation suitable for forming, whereas in T6/T651 the alloy achieves substantially higher yield and tensile strengths with reduced ductility. Fatigue behavior is favorable compared with many 6xxx alloys due to precipitate-stabilized microstructure and tighter control of impurities.

Yield-to-tensile ratios typically fall in the moderate range and elongation in peak tempers is sufficient for structural fasteners and fittings but not for severe stretch forming. Hardness increases markedly with solution treatment and aging; Brinell or Vickers hardness correlates well with observed tensile properties and is commonly used for incoming inspection. Thickness affects achievable properties because solution heat treatment and quench rates vary; thin sections reach near-peak properties after standard heat treatment while thick sections may show reduced aging response and lower strength.

Fatigue crack initiation is sensitive to surface finish, residual stresses, and microstructural heterogeneity, so post-processing such as shot-peening and controlled aging are standard for high-cycle applications. Fracture toughness in T6 is good for the strength level, aided by limited Cu content and controlled Fe/Mn impurity levels which reduce cleavage propensity.

Property	O/Annealed	Key Temper (T6 / T651)	Notes
Tensile Strength	~210–260 MPa	~380–440 MPa	T6/T651 are solution-treated and artificially aged to reach peak strength; values vary with section thickness
Yield Strength	~110–160 MPa	~320–380 MPa	Significant increase after aging; yield plateau influenced by ageing schedule
Elongation	~15–25%	~8–12%	Elongation decreases as strength increases; values depend on sample gauge and temper
Hardness	~60–80 HB	~120–150 HB	Brinell hardness correlates to temper; used for QA on batches and sections

Physical Properties

Property	Value	Notes
Density	~2.78 g/cm³	Typical for Al-Zn-Mg alloys; lower than many steels for high specific strength
Melting Range	~480–635 °C	Alloying widens solidus/liquidus range; watch for hot-cracking in castings
Thermal Conductivity	~130–150 W/m·K	Moderately high; slightly lower than 1xxx and 6xxx series due to alloying
Electrical Conductivity	~30–40 % IACS	Lower conductivity than pure Al; trades conductivity for strength
Specific Heat	~880–910 J/kg·K	Typical for aluminum alloys in ambient temperature range
Thermal Expansion	~23–24 µm/m·K (20–100°C)	Similar to other Al alloys; important for multi-material assemblies

The relatively high thermal conductivity and low density make EN AW-7020 attractive where heat dissipation and weight reduction are design drivers. Thermal expansion is typical of aluminum alloys and must be considered where the alloy interfaces with materials of different CTEs.

Melting and heat-treatment temperatures must be managed carefully in fabrication to avoid over-aging or incipient melting, especially for components with thin webs or thick sections where temperature gradients are significant.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6 mm	Thin sections reach full temper after standard aging	O, T5, T6, T651	Used for panels, extruded sections, and stamped parts
Plate	6–100+ mm	Thick plates may show reduced T6 response due to quench limitations	O, T6 (limited)	Heavy structural components; quench and aging must be tailored
Extrusion	Profiles up to several meters	Excellent uniformity in cross-section; responds well to T5/T6	T5, T6, T651	Common for structural profiles, rails and frames
Tube	Diameters varied; wall thickness 1–15 mm	Welded or seamless tubes can be aged to high strength	O, T6	Used in applications requiring lightweight structural members
Bar/Rod	Diameters up to 200 mm	Solid sections need controlled heat treatment for uniform properties	O, T6	Fasteners, fittings, and machined components

Sheets and extrusions are the most common product forms for EN AW-7020, benefiting from good extrudability and surface finish for anodizing. Plate and large cross-section products require bespoke heat-treatment cycles and aggressive quench controls to achieve uniform mechanical properties across the section.

The choice of product form affects processing routes: extrusions can be aged in-line to T5, while critical aerospace fittings often require solution heat treatment, quench and stretch followed by T6/T651 aging to minimize residual stresses and maintain dimensional accuracy.

Equivalent Grades

Standard	Grade	Region	Notes
AA	7020	USA	Common U.S. Aluminum Association designation for the alloy family
EN AW	7020	Europe	EN naming convention; often followed by temper codes such as T6 or T651
JIS	A7020	Japan	Localized standards reference similar composition and tempers
GB/T	7020	China	Chinese standard frequently uses same numerical designation with localized tolerances

Equivalents across standards are generally direct for wrought alloys like 7020, but procurement must account for regional specification nuances such as maximum impurity limits, tempering procedures, and required testing protocols. Small differences in guaranteed composition or heat-treatment acceptance criteria can lead to measurable differences in fatigue life and SCC performance.

When sourcing cross-border, specify the governing standard, temper, required mechanical properties, and any post-processing (e.g., stretching, anodizing) to ensure interchangeability and performance consistency.

Corrosion Resistance

EN AW-7020 offers better atmospheric corrosion resistance than many high-copper 7xxx alloys because its copper content is limited, reducing susceptibility to localized corrosion in normal environments. The alloy responds well to surface treatments such as anodizing and chromate conversion coatings which further enhance barrier protection and paint adhesion. In industrial atmospheres, moderate protection and periodic maintenance result in long service life for structural parts.

In marine environments the alloy performs acceptably but is not as robust as 5xxx magnesium-rich alloys or properly treated 6xxx series for long-term immersion service. Chloride-induced pitting and intergranular corrosion are mitigated by careful control of quench and aging and by use of protective coatings. Stress corrosion cracking (SCC) potential exists for 7xxx alloys under tensile residual stress and corrosive environments, but 7020’s lower Cu and controlled impurity profile reduce but do not eliminate SCC risk.

Galvanic interactions follow standard aluminum behavior: pairing with nobler materials such as stainless steels or copper can accelerate local corrosion if electrical continuity and electrolyte presence occur. Use of insulating barriers, sacrificial anodes, or selective coatings is recommended where dissimilar metals are joined. Compared with 6xxx alloys, 7020 trades a modest reduction in corrosion resistance for higher strength and improved fatigue performance.

Fabrication Properties

Weldability

EN AW-7020 can be welded by TIG and MIG processes, but the alloy is sensitive to hot cracking and HAZ softening; therefore, welding is commonly performed in softer tempers and followed by local or full re-aging where practical. Recommended filler alloys are those that provide adequate ductility and corrosion resistance, typically Al-Mg (e.g., 5356) or Al-Si fillers for specific joint types; filler selection affects post-weld strength and SCC resistance. For aerospace or high-strength structural applications, welding is often avoided in favor of mechanical joining due to loss of temper in the HAZ.

Machinability

Machinability of EN AW-7020 is rated as moderate to good in annealed condition and somewhat reduced in T6 tempers due to higher hardness and strength. Carbide tooling with positive rake geometry and controlled feeds provide best life; high-speed steel can be used for softer tempers. Chip control is generally good but can be affected by section changes and heat treatment; coolant and rigid fixturing improve surface finish and tool life.

Formability

Cold formability is excellent in the O temper and decreases as the alloy is aged to higher-strength states; for complex bends and deep draws, O or H-series tempers are preferred. Minimum bend radii depend on thickness and temper but typically require larger radii in T6 to avoid cracking; pre-heating or warm-forming can improve ductility for moderate forming. Springback is more pronounced at higher strength levels and must be compensated for in tool design.

Heat Treatment Behavior

As a heat-treatable alloy, EN AW-7020 responds to solution heat treatment, quenching, and artificial aging to develop its peak-strength precipitate microstructure. Typical solution treatment temperatures are in the range of 470–480 °C with time adjusted by section thickness to enable dissolution of soluble phases. Rapid quenching (water quench or similar) from solution temperature is necessary to retain solute in supersaturated solid solution prior to aging.

Artificial aging for T6 temper is commonly performed at 120–160 °C for times ranging from 8 to 24 hours depending on desired strength-toughness balance. T5 temper denotes air/water-cooled from hot working and directly artificially aged. T651 indicates T6 followed by a controlled stretching operation to reduce residual stresses and improve dimensional stability. Improper heat treatment or slow quench rates lead to coarse precipitates, lower strength and poorer fracture and fatigue behavior.

For non-heat-treatment operations, work-hardening provides only limited strength increases compared with full precipitation hardening, and annealing (O temper) is used to restore ductility prior to forming or machining.

High-Temperature Performance

Elevated temperature exposure progressively reduces the precipitate-strengthened hardness and yield strength of EN AW-7020, with significant strength loss occurring above approximately 120–150 °C. Service at temperatures above typical artificial aging ranges can cause over-aging, coarsening of strengthening precipitates and consequent reductions in mechanical properties and fatigue resistance. For components exposed to sustained elevated temperatures, selection of alternative alloys or protective design measures is recommended.

Oxidation is minimal in normal atmospheric conditions due to aluminum’s passive oxide, but prolonged high-temperature exposure can alter surface finish and reduce corrosion protection, especially in chloride-containing environments. The HAZ produced by welding can exhibit localized softening and reduced high-temperature performance; post-weld heat treatment may partially restore properties but is sometimes impractical for large assemblies.

Creep resistance is limited at elevated temperatures compared with steels and nickel alloys; design must account for long-term dimensional changes if operating near the upper temperature capability of the alloy.

Applications

Industry	Example Component	Why EN AW-7020 Is Used
Automotive	Structural extruded rails and crash management parts	High strength-to-weight and good extrudability for complex profiles
Marine	Superstructure components and fittings	Balanced strength and improved atmospheric corrosion resistance vs 7xxx with higher Cu
Aerospace	Fittings, lugs, and secondary structural elements	High specific strength with good fatigue properties and capacity for precision heat treatment
Electronics	Chassis and heat spreaders	Good thermal conductivity combined with stiffness for lightweight housings

EN AW-7020 is selected for components that require higher strength than 6xxx alloys while still needing reasonable corrosion behaviour and good extrudability. Its use in extruded structural profiles and machined fittings leverages the alloy’s ability to reach high strength in T6/T651 tempers while maintaining serviceable toughness and fatigue life.

Selection Insights

Choose EN AW-7020 when you need a heat-treatable aluminum with higher strength than 6xxx series alloys but with better corrosion resistance than high-copper 7xxx alloys. It is a solid choice for extrusions and machined fittings where T6/T651 strength and fatigue resistance are prioritized over maximum weldability.

Compared with 1100 (commercially pure Al), EN AW-7020 trades electrical and thermal conductivity and superior formability for much higher strength and stiffness. Against work-hardened alloys like 3003 or 5052, 7020 offers significantly higher strength at the cost of reduced forming ease and somewhat greater susceptibility to SCC. Versus common heat-treatable 6061/6063, 7020 delivers higher peak strength and fatigue performance for structural applications, although 6061 may be preferred where weldability and corrosion resistance in marine environments are more critical.

Specifiers should weigh strength, corrosion environment, weldability needs, and post-processing capability (heat treatment and machining) when selecting 7020; it is particularly advantageous where extrusion geometry and T6/T651 strength-to-weight are decisive.

Closing Summary

EN AW-7020 remains a relevant engineering alloy by offering a balanced combination of high specific strength, good fatigue resistance, and acceptable corrosion performance for structural applications where manufacturability via extrusion or machining is critical. Its controlled composition and heat-treatment response make it a practical alternative to higher-copper 7xxx alloys and to lower-strength 6xxx series materials in demanding lightweight structural designs.