Aluminum 713: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 713 is positioned within the high-strength, heat-treatable family of aluminum alloys and is most closely aligned with the 7xxx series chemistry and performance envelope. It is primarily alloyed with zinc as the major strengthening element, alloyed with magnesium and copper to produce a precipitation-hardening microstructure.

The primary strengthening mechanism for 713 is age hardening via solution treatment followed by controlled quench and artificial aging; it exhibits pronounced strengthening through the formation of coherent and semi-coherent MgZn2 (eta) phase precipitates. Key traits include high tensile and yield strength for its density, moderate to poor intrinsic corrosion resistance compared with 5xxx/6xxx alloys, and limited but workable formability in softer tempers; weldability requires care to avoid HAZ softening and cracking.

Typical industries for alloy 713 are aerospace structural fittings, high-performance automotive components, defense hardware and some marine or sports equipment where strength-to-weight ratio is critical. The alloy is selected over lower-strength alloys when peak static and fatigue strength, stiffness and damage tolerance per weight are higher design priorities than absolute corrosion resistance or ease of welding.

Designers choose 713 when the application demands maximum strength from an aluminum solution-treatable alloy with relatively predictable aging response, and where post-weld mechanical restoration or corrosion mitigation (coatings, anodizing, sacrificial alloys) can be applied.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (12–20%)	Excellent	Excellent	Fully annealed, best for forming and drawing
H14	Medium	Moderate (8–12%)	Good	Fair	Strain-hardened, limited additional strengthening
T5	Medium-High	Moderate (6–10%)	Moderate	Fair	Cooled from hot working and artificially aged
T6	High	Lower (6–10%)	Fair to poor	Limited	Solution treated + artificial aging; peak strength
T651	High	Lower (6–10%)	Fair to poor	Limited	T6 with stress relief by stretching to stabilize properties
H112	Variable	Variable	Variable	Variable	As-fabricated temper; vendor-controlled condition

Temper strongly controls the mechanical envelope of 713: annealed O tempers maximize ductility and formability at the cost of strength, while T6/T651 deliver peak yield and tensile strengths with concomitant reductions in elongation and bendability. Selection of temper is an engineering compromise between required forming operations, final service strength and susceptibility to phenomena such as stress-corrosion cracking and HAZ softening after welding.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.40	Impurity; affects casting fluidity and hardenability marginally
Fe	≤ 0.50	Fe-rich intermetallics can reduce toughness and fatigue life
Mn	≤ 0.30	Minor grain-structure modifier; limited solid solution strengthening
Mg	2.0–2.9	Key component for MgZn2 precipitates; controls aging kinetics
Cu	1.2–1.8	Raises strength and hardness, can reduce corrosion resistance
Zn	5.1–6.5	Principal strength alloying element forming Mg-Zn precipitates
Cr	0.10–0.30	Controls recrystallization and grain structure, improves toughness
Ti	≤ 0.10	Grain refiner during casting or primary processing
Others (each)	≤ 0.05–0.15	Trace additions and residual elements; balance Al

The nominal chemistry of 713 is tuned for precipitation hardening: zinc and magnesium combine to form the dominant strengthening phases during aging, while copper increases peak strength and contributes to hardness at the expense of some corrosion resistance. Chromium and trace titanium act as microstructure stabilizers to refine grains and reduce susceptibility to recrystallization during thermomechanical processing.

Mechanical Properties

In tensile behavior, 713 exhibits a strong dependence on temper and section thickness. In peak-aged T6/T651 conditions the alloy develops high ultimate tensile strength and significant yield strength with modest elongation, whereas annealed material has much lower strength but superior ductility and toughness. The stress-strain curve typically shows limited uniform plasticity before localized necking in high-strength tempers but retains reasonable modulus and elastic behavior comparable to other aluminum grades.

Yield strength and tensile strength are sensitive to aging parameters and section thickness; thicker sections cool more slowly during quench, which can reduce achievable peak hardness and shift aging kinetics. Hardness is commonly used as a shop-floor proxy for temper and tensile level, with Brinell or Vickers indentation correlating to tensile data. Fatigue performance is competitive for the class when surface finish and residual stress state are well controlled, but fatigue life is strongly affected by corrosion, notches and cold-working history.

Property	O/Annealed	Key Temper (e.g., T6 / T651)	Notes
Tensile Strength (UTS)	240–320 MPa	520–590 MPa	T6/T651 peak-aged values depend on thickness and aging schedule
Yield Strength (0.2% offset)	110–200 MPa	450–540 MPa	Yield increases dramatically from O to T6; HAZ can drop yield locally
Elongation (in 50 mm)	12–20%	6–12%	Elongation reduced by aging and cold work; measurement method matters
Hardness (HB)	60–80 HB	140–170 HB	Brinell ranges approximate; hardness correlates with tensile properties

Physical Properties

Property	Value	Notes
Density	2.80 g/cm³	Typical for high-strength Al-Zn-Mg-Cu alloys; excellent specific strength
Melting Range	~500–635 °C (solidus to liquidus)	Alloying depresses liquidus slightly below pure Al; casting margin important
Thermal Conductivity	~120–140 W/m·K	Lower than 6xxx and pure Al but still good for heat spreading
Electrical Conductivity	~30–35% IACS	Reduced by alloying; typical for 7xxx-class alloys
Specific Heat	~0.88 J/g·K	Comparable to other wrought aluminum alloys
Thermal Expansion	~23.2 µm/m·K	Near typical aluminum values; design for thermal strain is required

The physical property set places 713 as a lightweight, thermally conductive structural metal with predictable expansion and heat capacity for thermal management roles. Reduced electrical conductivity relative to purer aluminum limits its use in high-current conductors, but thermal conductivity remains adequate for many heat-sink applications when mechanical strength is required alongside thermal performance.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Uniform thin-section strengths; favorable for cold-forming in O/H tempers	O, H14, T5, T6	Widely used for panels and skin components
Plate	6–200+ mm	Thickness effects significant; thicker plates may not reach full T6 strength without specialized quench	O, T6, T651	Structural applications require careful quench control
Extrusion	Cross-sections up to several hundred mm	Mechanical properties vary with TMT and aging; directional anisotropy possible	T5, T6, H112	Long profiles for frames and stiffeners
Tube	Ø10–200 mm	Properties sensitive to manufacturing (seamless vs welded) and subsequent heat treat	T6, T651	Hydraulic, structural and transport tubing
Bar/Rod	Ø5–100 mm	Typically produced in T6 or O; response to aging predictable	O, T6	Fasteners, fittings, machined components

Sheets and thin gauges are generally easy to form and achieve consistent mechanical performance, whereas plates and thick extrusions require attention to quench rates and distortion during solution treatment. Extrusions and bars are often aged downstream (T5/T6) to optimize strength, whereas welded tubes and structural members need post-weld heat treatment or design allowances for HAZ softening.

Equivalent Grades

Standard	Grade	Region	Notes
AA	713	USA	Designation used for this proprietary/industry grade; closely aligned with 7xxx class behavior
EN AW	—	Europe	No exact EN equivalent; nearest common comparators are EN AW-7075 and EN AW-7050
JIS	—	Japan	No direct JIS equivalent; comparison often made to A7075 alloys for mechanical behavior
GB/T	—	China	No direct GB/T equivalent; Chinese 7xxx-series alloys show similar chemistry and performance

There is no single global standard that maps one-to-one with 713; instead engineers typically reference established 7xxx family alloys (7075, 7050) to infer behavior for design, procurement and certification. Small differences in limits for copper, zinc and magnesium and the presence of micro-alloying elements (Cr, Zr, Ti) create meaningful distinctions in aging response, toughness and SCC susceptibility that must be confirmed with supplier material certifications.

Corrosion Resistance

In atmospheric environments alloy 713 performs reasonably when protected by coatings, paints or anodic films, but bare metal exposure tends to show pitting and exfoliation more readily than 5xxx and 6xxx series alloys. The Cu content and high-strength precipitate structure increase susceptibility to localized corrosion and intergranular attack particularly in cyclic wet/dry or chloride-bearing atmospheres.

Marine exposure requires caution: with suitable surface protection and cathodic/anodic isolation the alloy can be used in mildly aggressive environments, but in continuous immersion or splash zones stainless steel or 5xxx alloys are often preferred. Stress corrosion cracking is a real concern for high-strength tempers (T6/T651), especially under tensile residual stresses and elevated chloride concentration; design mitigation includes reducing tensile stresses, using lower-strength tempers, or applying protective systems.

Galvanic coupling with more noble materials (stainless steels, copper alloys) can accelerate localized corrosion of 713; sacrificial coatings or insulating barriers are recommended for mixed-metal assemblies. Compared to 3xxx/5xxx families, 713 trades superior mechanical properties for lower innate corrosion resistance and requires system-level corrosion engineering.

Fabrication Properties

Weldability

Welding of 713 is challenging in high-strength tempers. Standard fusion welding processes (TIG/MIG) result in significant HAZ softening and loss of peak properties near the weld, and the alloy is prone to hot cracking unless filler selection and joint design are optimized. Use of low-strength filler alloys (e.g., 5356 or 4043 equivalents for aluminum) reduces cracking risk but produces joints with a strength lower than the base metal; post-weld heat treatment and mechanical restoration techniques are necessary for structural recovery when feasible.

Machinability

Machining 713 in T6/H tempers is generally good compared with many high-strength steels but requires robust tooling and coating due to high strength and work-hardening tendency at the cut face. Carbide tools with positive rake and controlled chip-breakers are effective, with moderate cutting speeds and higher feed to avoid built-up edge. Surface finishes achievable are excellent; however, clamping and workholding must control distortion to maintain dimensional tolerances.

Formability

Forming is most effective in O or soft H tempers; bend radii should be governed by temper and thickness with R/t ratios typically larger in T6 states. Cold formability deteriorates rapidly with aging and Cu content, so designers commonly form in soft tempers and then perform final solution/aging sequences when geometry and residual stresses permit. Hydroforming and stretch-forming are practical for complex shapes when using annealed material and controlled strain paths.

Heat Treatment Behavior

Alloy 713 is a heat-treatable alloy exhibiting classical T-temper transitions: solution heat treatment dissolves soluble phases and prepares a supersaturated solid solution, quenching preserves that state, and artificial aging precipitates strengthening phases. Typical solution treatment temperatures are in the 470–490 °C range followed by rapid quench to room temperature to minimize coarse precipitate formation.

Artificial aging schedules for peak T6 strength commonly use 120–180 °C for several hours; variations produce T5-like or underaged conditions for improved toughness and reduced SCC susceptibility at some strength loss. The T651 variant includes a controlled stretch to relieve residual stresses after quenching and before aging, stabilizing dimensions for structural applications.

If annealing is required, a full softening heat treatment (O) is performed at temperatures near 340–400 °C with slow cooling to recrystallize and restore ductility; work hardening via cold deformation provides alternative non-heat-treatment paths for moderate strength increases when thermal treatments are impractical.

High-Temperature Performance

Strength of 713 begins to degrade noticeably above approximately 120–150 °C as precipitate stability changes and coarsening of strengthening phases reduces yield and UTS. Continuous service temperatures above ~150 °C are generally avoided for load-bearing components unless specific high-temperature tempers are developed. Oxidation in air is limited due to natural alumina formation, but higher temperatures accelerate surface scale formation and may alter fatigue crack initiation behavior.

HAZ behavior under localized high heat inputs (welding) can produce soft bands and precipitate dissolution which require post-process heat treatments to recover properties for critical components. Creep resistance at elevated temperature is limited; for long-term thermal loading designers often choose heat-resistant aluminum alloys or alternate materials for components that must retain substantial strength above ambient temperatures.

Applications

Industry	Example Component	Why 713 Is Used
Automotive	High-performance suspension arms, structural cross-members	High specific strength and stiffness for lightweighting
Marine	Rudder stocks, high-strength brackets	Strength-to-weight and reasonable corrosion resistance with coatings
Aerospace	Fittings, flap tracks, landing gear components (non-primary)	High static and fatigue strength, good machinability
Electronics	Heat spreaders and structural chassis	Good thermal conductivity combined with higher strength

Across these sectors 713 is chosen where stiffness and strength per unit mass drive design decisions and where surface protection strategies can be implemented to manage corrosion risks. The alloy is particularly useful where machining and secondary processing are required to produce complex, load-bearing parts.

Selection Insights

Select alloy 713 when the design prioritizes peak specific strength and when age-hardening processes and controlled thermal treatments can be integrated into manufacturing. Specify softer tempers for forming operations and plan final aging to achieve the needed mechanical performance.

Compared with commercially pure aluminum (1100), 713 trades higher strength and stiffness for reduced electrical conductivity and diminished formability in peak tempers. Compared with common work-hardened alloys like 3003 or 5052, 713 achieves much higher strength and fatigue resistance but has lower inherent corrosion resistance and requires thermal processing. Compared with heat-treatable alloys such as 6061 or 6063, 713 reaches higher peak strength at similar densities but often at the expense of toughness, weldability and SCC susceptibility; choose 713 when strength-to-weight outweighs these trade-offs.

Closing Summary

Alloy 713 remains a valuable high-strength, heat-treatable aluminum choice where maximum mechanical performance per unit mass is required and manufacturing processes can control heat treatment, surface protection and residual stresses. Its engineered chemistry provides designers with a powerful balance of tensile strength, machinability and thermal performance when system-level corrosion and joining strategies are incorporated.