Aluminum 7034: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

7034 is a 7xxx-series aluminum alloy, placed in the high-strength Al-Zn-Mg(-Cu) family where zinc is the primary alloying addition. Its designation indicates a Zn–Mg–Cu precipitation-hardenable system that is engineered to deliver elevated yield and tensile strength compared with 1xxx–6xxx families while retaining a favorable strength-to-weight ratio.

Strengthening in 7034 is achieved principally through solution heat treatment, rapid quenching and artificial aging to form fine η (MgZn2)-type precipitates; this T-type heat-treatable mechanism yields high specific strength but introduces sensitivity to thermal cycles and localized corrosion. Typical traits include high static strength in peak tempers, moderate-to-poor as-welded retention of mechanical properties, variable formability depending on temper, and mid-range corrosion resistance that can be improved by over-aging and microalloy additions.

Industries that commonly use alloys like 7034 include aerospace airframe fittings and forgings, high-performance automotive substructures and suspension components, defense hardware, and specialized sporting equipment where high static strength and stiffness are prioritized. The alloy is selected over lower-strength series (3000/5000/6000) where design requires reduced cross-section, weight saving, or higher allowable stresses, and over 7075-like alloys where slight trade-offs in peak strength are accepted for better toughness or SCC resistance.

7034 is chosen when engineers need a heat-treatable aluminum that can be processed to high static strengths with controlled over-aging options to reduce susceptibility to stress-corrosion cracking; it occupies a practical niche between maximum-strength 7xxx alloys and more corrosion-resistant or formable families.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for forming and machining
H14	Moderate	Moderate	Good	Good	Work-hardened and partially annealed for formed parts
T4	Moderate	Moderate	Good	Good	Naturally aged after solution treatment; intermediate strength
T6	High	Low–Moderate	Fair	Poor	Solution treated and artificially aged to peak strength
T651	High	Low–Moderate	Fair	Poor	T6 with stress-relief by stretching; common for structural parts
T73	Moderate–High	Moderate	Fair	Poor	Over-aged to improve corrosion and SCC resistance
T76	Moderate	Moderate	Fair	Poor	Stabilized temper for improved stress-corrosion performance

Tempers in 7034 exert strong control over the precipitate state, which directly determines yield strength, toughness and SCC resistance. Peak-aged tempers such as T6 and T651 maximize tensile properties but reduce ductility and formability and increase susceptibility to localized corrosion and stress-corrosion cracking.

Over-aged tempers like T73/T76 trade some peak strength for improved resistance to stress-corrosion cracking and better long-term stability; annealed and work-hardened tempers (O, Hxx) provide the best formability and machinability at the expense of specific strength.

Chemical Composition

Element	% Range	Notes
Si	0.00–0.50	Typical impurity; controls casting/filtration behavior
Fe	0.00–0.50	Impurity, affects intermetallic particle content and toughness
Mn	0.00–0.20	Minor effect in 7xxx alloys; may aid grain structure slightly
Mg	1.40–2.20	Primary strengthening partner with Zn (forms MgZn2)
Cu	1.00–1.80	Raises strength and hardness; increases SCC sensitivity if high
Zn	4.50–5.50	Principal strengthening element in 7xxx family
Cr	0.05–0.25	Controls recrystallization and grain structure; improves toughness
Ti	0.00–0.15	Grain refiner in cast/ingot metallurgy
Others (incl. Zr)	0.00–0.30	Zr often used to control grain growth and improve toughness

The high Zn and Mg content establishes the precipitation-hardening potential through η-phase formation; Cu is used to tailor peak-strength levels and precipitate morphology but must be balanced because elevated Cu increases susceptibility to intergranular corrosion and SCC. Chromium and zirconium additions are intentionally kept low to pin recrystallization, refine grain structure and provide more uniform mechanical behavior across gauges and processing routes. Impurity levels of Si and Fe are controlled to limit coarse intermetallic particles that degrade toughness and fatigue performance.

Mechanical Properties

In tensile behavior 7034 exhibits a marked difference between annealed and peak-aged tempers: the alloy shows pronounced increases in both tensile and yield strength after solution heat treatment and artificial aging, with a concurrent reduction in uniform elongation. Yield-to-ultimate ratios are typical of precipitation-hardened alloys, with relatively low ductility in T6/T651 conditions and modest to good toughness in over-aged tempers like T73.

Hardness follows the same trend, with annealed material being soft and easy to machine/form, and T6 reaching substantially higher HB values; fatigue strength benefits from fine, evenly distributed precipitates but is negatively affected by coarse intermetallics and surface defects. Thickness and section size influence attainable properties due to quench sensitivity—thicker sections cool more slowly, producing coarser precipitates and lower as-quenched strength unless special quench strategies or microalloying are used.

Temper and processing strongly dictate notch sensitivity and fatigue crack initiation behavior; careful control of surface finish, shot-peening, and post-heat-treatment stress-relief are commonly applied to optimize fatigue life for critical components.

Property	O/Annealed	Key Temper (T6/T651)	Notes
Tensile Strength (MPa)	120–260	480–540	T6 range depends on section and exact chemistry
Yield Strength (MPa)	80–220	415–480	Yield is high in peak tempers, work hardening increases YS
Elongation (%)	20–30	6–12	Ductility falls as strength increases
Hardness (HB)	35–60	140–165	Hardness correlates with aging condition and precipitate state

Physical Properties

Property	Value	Notes
Density	2.78 g/cm³	Typical for high-strength Al alloys; good specific strength
Melting Range	477–635 °C	Solidus/liquidus span influenced by alloying additions
Thermal Conductivity	~120–140 W/m·K	Lower than pure Al; adequate for many thermal applications
Electrical Conductivity	~28–36 %IACS	Reduced compared with pure Al due to alloying elements
Specific Heat	~0.88 J/g·K	Near-aluminum base values at room temperature
Thermal Expansion	~23–24 ×10^-6 /K	Typical linear expansion near other Al alloys

The physical property set confirms 7034 as a low-density structural metal with reasonable thermal transport capability and moderate electrical conductivity; these traits favor weight-sensitive designs that may also require heat dissipation. Thermal conductivity and electrical conductivity are reduced relative to commercially-pure aluminum because of solute scattering and second-phase particles, and these reductions must be considered in thermal management and electrical applications.

The melting range indicates standard aluminum processing temperatures for melting and casting, while forming and heat-treatment windows follow typical Al-Zn-Mg-Cu processing guidelines with solution treatment near the solidus limit but below incipient melting.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–8 mm	Sensitive to rolling and quench; good uniformity in thin gauges	O, T4, T6, T651	Widely used for structural panels; thin gauges achieve T6 well
Plate	8–200+ mm	Strength reduced in very thick sections due to quench	O, T6, T73	Thicker plate requires controlled quenching or over-aging
Extrusion	Cross-sections up to several 100 mm	Less common than 6xxx; quench sensitivity limits large profiles	T6 (limited), O	Large-section extrusions are challenging due to hot cracking
Tube	OD from small to large	Behavior similar to extrusions; welding often used for fabrication	O, T6 (welded)	Seamless tubes possible but limited by alloy formability
Bar/Rod	Diameters up to 150 mm	Good for forgings and machined components	O, T6, T651	Used for high-strength forgings and machined fittings

Different product forms impose distinct constraints on achievable properties and processing routes; sheet and thin plate cool rapidly and can achieve near-peak T6 properties, while thicker plate and extrusions are limited by quench rate and often require over-aging or thermomechanical control to stabilize properties. Forging and cold-forming routes are used to refine microstructure and improve fatigue life, but these operations must be coordinated with subsequent solution treatment and aging to avoid unwanted softening or distortion.

Welding and joining routes are often chosen to minimize HAZ softening; when welding is unavoidable, design and filler selection are critical to preserve structural integrity while accepting local reductions in mechanical properties.

Equivalent Grades

Standard	Grade	Region	Notes
AA	7034	USA	Primary designation for this alloy in Aluminum Association listings
EN AW	7034	Europe	Generally equivalent chemistry designation under EN standards
JIS	A7075 (approx)	Japan	A7075 is not identical but is a common reference for high-strength 7xxx families
GB/T	7A04 / 7A09 (approx)	China	Similar 7xxx-series grades used in China; direct equivalence must be verified

Exact cross-reference between standards is complicated by differences in permitted impurity levels, microalloying elements and typical processing routes; while EN AW-7034 will be chemically similar, JIS and GB/T grades listed are approximate functional analogues rather than strict chemical equivalents. Engineers should confirm specific supplier certification and chemical analysis for interchangeability, and be aware that processing history (e.g., ingot metallurgy, thermo-mechanical treatment) can create performance differences even when nominal chemistry matches.

Corrosion Resistance

Atmospheric corrosion resistance for 7034 is moderate; painted or coated surfaces perform well in urban and industrial atmospheres but bare alloy will exhibit pitting and intergranular corrosion more readily than Al-Mg (5xxx) alloys. The intermetallic-rich grain boundaries typical of high-Zn alloys can form anodic sites under corrosive exposure, so surface protection and design to avoid crevices are standard practice.

In marine or chloride-laden environments 7034 is more vulnerable than 5000-series alloys; susceptibility may be mitigated by specifying over-aged tempers (T73, T76) and strict surface finishing protocols. Cathodic protection and polymeric barriers are common for long-term performance of critical parts in marine service.

Stress corrosion cracking (SCC) is a key concern for high-strength 7xxx alloys: peak-aged conditions show the highest susceptibility, while controlled over-aging, lowered Cu content and microalloy additions (Cr, Zr) substantially reduce the SCC risk. Galvanic interactions with dissimilar metals (e.g., steel, copper) are significant—galvanic separations or insulating layers are required to prevent accelerated anodic dissolution of the aluminum alloy.

Fabrication Properties

Weldability
Welding 7034 is challenging because the heat input creates a softened HAZ and introduces hot-cracking risk in fusion welds; filler choice and pre/post treatments are critical to minimize these effects. TIG and MIG welding are possible with 5xxx or specially formulated 7xxx-compatible fillers, but designers should expect a significant reduction in local mechanical properties and potentially increased susceptibility to localized corrosion.

Machinability
Machinability of 7034 in annealed and H-tempers is good to very good; in T6 the alloy machines well with appropriate carbide tooling and rigid setups but tool wear increases with hardness. Recommended practices include positive rake carbide inserts, high-pressure coolant, moderate to high surface speeds and chip breakers to control serrated chips typical of precipitation-hardened alloys.

Formability
Forming is best performed in O or T4 conditions—cold-forming T6 material results in cracking or springback and is generally not recommended unless significant over-design is provided. Typical minimum bend radii for sheet in T4/O are on the order of 1–3× material thickness depending on edge condition, whereas T6 may require radii of 4–6× thickness or annealing prior to forming.

Heat Treatment Behavior

As a heat-treatable alloy, 7034 follows standard solution treatment, quench and artificial aging sequences to develop peak properties. Solution treatment is typically conducted near 470–485 °C to dissolve soluble phases, followed by rapid quenching to trap solute in supersaturation; the rate of quench is critical, particularly for thicker sections, to avoid coarse precipitate formation and retain hardenability.

Artificial aging schedules vary: a common T6-like aging is 120–125 °C for 18–24 hours to achieve near-peak hardness and strength, whereas T73/T76 over-aging cycles use elevated aging temperatures or extended times to create a coarser, more stable precipitate population that reduces SCC susceptibility. T651 designations indicate a stress-relief stretching step after quench prior to aging to minimize residual distortion.

High-Temperature Performance

7034 retains useful mechanical properties up to moderate elevated temperatures but experiences significant strength loss above approximately 150–175 °C as precipitates coarsen and dissolve. For continuous service at elevated temperatures designers should consider alloys specifically designed for thermal stability or apply protective surface treatments to reduce oxidation and creep.

Oxidation resistance at service temperatures is typical of aluminum alloys due to a stable Al2O3 film, but long-term exposure to high temperatures accelerates microstructural changes in the precipitation system and can cause permanent softening; HAZ regions adjacent to welds suffer pronounced property degradation when exposed to thermal cycles.

Applications

Industry	Example Component	Why 7034 Is Used
Aerospace	Fittings and forgings	High static strength-to-weight and good fatigue performance in optimized tempers
Automotive	Suspension components and chassis parts	High strength for reduced section thickness and improved NVH when fatigue-treated
Marine	Structural brackets and outriggers	Good strength with proper over-aging and surface protection
Electronics	Structural panels and housings	Balance of thermal conductivity and rigidity for lightweight enclosures

7034 is commonly selected for applications requiring high static strength, tight dimensional stability and good fatigue performance after appropriate heat treatment and surface finishing. The ability to tailor properties through temper choice (peak aging vs over-aging) allows designers to prioritize either maximum strength or improved corrosion/SCC resistance depending on service demands.

Selection Insights

Choose 7034 when the design driver is high specific strength combined with the ability to tailor long-term corrosion resistance through temper control; it is especially useful when weight reduction will provide system-level benefits. Consider cost and availability trade-offs—7034 can be more expensive and less available in large extrusions compared with 6xxx-series alloys, and welding or repair welding will require special procedures.

Compared with commercially pure aluminum (1100), 7034 trades much higher strength and stiffness for