Aluminum 1085: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 1085 is part of the 1xxx series of aluminum alloys and is classified as a commercially pure aluminum with a nominal minimum aluminum content of approximately 99.85%. As a member of the near-pure aluminium family, the alloy belongs to the 1000-series where impurity limits and trace alloying are used primarily to control properties such as grain structure and workability rather than to provide alloy-derived strengthening. The major alloying constituents are residual levels of iron and silicon with trace amounts of copper, manganese, magnesium, zinc, chromium and titanium typically controlled to very low limits.

1085 is not a heat‑treatable alloy; its mechanical strength is derived almost entirely from solid solution characteristics and from work hardening through cold deformation. Key traits include excellent electrical and thermal conductivity, superior formability in annealed tempers, and good corrosion resistance in atmospheric and mildly corrosive environments. Weldability is generally excellent for fusion processes when proper fillers and techniques are used, but mechanical strength in welded zones is governed by subsequent cold working rather than aging.

Typical industries using 1085 include electrical conductor manufacturing (bus bars, strips, and foils), heat-exchange and thermal management components, packaging and foil, and architectural applications where ductility and corrosion resistance are more important than peak strength. Design engineers select 1085 when conductivity and formability are prioritized over the higher strength available from alloyed or heat-treatable materials; its purity gives predictable corrosion behavior and stable dimensional performance in forming and joining operations.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, maximum ductility for deep drawing
H12	Low-Medium	Medium-High	Very Good	Excellent	Light strain hardening, retains good formability
H14	Medium	Medium	Good	Excellent	Common commercial strain-hardened temper for balance of strength and formability
H16	Medium-High	Medium-Low	Fair	Excellent	Higher strain hardening for added strength where moderate formability is acceptable
H18	High	Low	Limited	Excellent	Near full-hard, used for high-strength strip and foil applications
H19	Very High	Very Low	Poor	Excellent	Maximum commercially applied cold work for highest strength in non-heat-treatable alloys

Temper selection controls the balance between ductility and strength primarily via cold work. Annealed (O) temper maximizes elongation and formability for deep drawing, spinning, and severe bending operations; progressively higher H tempers increase yield and tensile strength by controlled cold deformation while progressively reducing elongation.

For fabricated parts that require post‑weld forming or severe cold deformation, O or light H tempers are specified prior to forming; final mechanical properties can often be achieved by selecting the appropriate degree of strain hardening in the chosen H temper rather than by thermal treatment.

Chemical Composition

Element	% Range	Notes
Si	0.05 max	Controlled low Si for reduced casting/impurity effects
Fe	0.25 max	Primary impurity; affects strength and grain structure
Mn	0.05 max	Often negligible; can influence grain stability if present
Mg	0.05 max	Kept minimal to avoid unintended precipitation strengthening
Cu	0.05 max	Controlled low to preserve corrosion resistance and conductivity
Zn	0.05 max	Low levels to avoid galvanic and strength effects
Cr	0.05 max	Trace control for grain refinement in some production routes
Ti	0.03 max	Used in small amounts for grain refinement in cast or wrought stock
Others	Individual 0.03 max; total 0.15 max	Each residual element limited to maintain high Al purity

1085 is essentially an aluminum balance alloy where Al content is about 99.85% minimum and the remainder comprises trace impurities. The low levels of Si and Fe primarily influence as-cast grain structure and formability, while strict control of Cu, Mg and Zn preserves electrical conductivity and corrosion resistance. Small additions or residuals of Ti and Cr are commonly used to refine grains during casting and rolling, improving surface quality and mechanical consistency without materially changing the alloy class behavior.

Mechanical Properties

As a near‑pure aluminum, 1085 exhibits low yield and tensile strengths in the fully annealed condition and shows significant increases in strength through cold working (H tempers). Tensile behavior is characterized by a low elastic limit and high ductility in O temper; yield and ultimate tensile strength rise with greater degrees of strain hardening but elongation falls concurrently. The lack of precipitation hardening means there are no heat treatment paths to significantly increase peak strength; mechanical performance is therefore process-dependent and repeatable via temper control.

Hardness values track closely with tensile strength and cold work; typical Brinell or Vickers hardness increases linearly with hardness induced by deformation processes. Fatigue performance of 1085 is moderate — good for many low-stress cyclic applications — but the fatigue limit is lower than alloyed structural aluminium grades; fatigue life benefits from smooth surface finishes and compressive surface treatments. Thickness effects are pronounced: thin foils and strips take higher cold work levels for strength and exhibit higher apparent hardness per unit strain, whereas thicker sections require more substantial deformation to reach comparable strength and can retain higher toughness in the core.

Property	O/Annealed	Key Temper (e.g., H14)	Notes
Tensile Strength	~60–90 MPa	~120–170 MPa	Values depend on thickness and exact cold work; H16/H18 higher
Yield Strength	~20–40 MPa	~80–140 MPa	Yield increases with H temper; low in annealed state
Elongation	~35–45%	~8–25%	Annealed grades are highly ductile; H tempers reduce elongation
Hardness	~15–25 HB	~30–50 HB	Brinell approximations; varies with cold work and thickness

Physical Properties

Property	Value	Notes
Density	2.71 g/cm³	Typical for aluminium alloys; affects mass-sensitive design
Melting Range	~660 °C	Near-pure aluminium melting point ~660.3 °C
Thermal Conductivity	~220–235 W/m·K	High thermal conductivity, useful for heat-sinks and exchangers
Electrical Conductivity	~60–65% IACS	Very good conductivity owing to high purity
Specific Heat	~900 J/kg·K	Approximate at room temperature; useful for thermal calculations
Thermal Expansion	~23.0 ×10^-6 /K	Typical linear expansion coefficient for aluminium alloys

1085's high thermal and electrical conductivities are among its most important engineering attributes, making it a preferred material for electrical and thermal management components. The relatively low density combined with good thermal properties offers excellent specific conductivity and specific thermal capacity for lightweight thermal systems. Designers must account for aluminum's relatively high thermal expansion in assemblies with dissimilar materials; appropriate allowances and joining strategies mitigate differential expansion issues.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2 mm – 6 mm	Thin sheets respond quickly to cold work	O, H12, H14, H16	Widely used for architectural facings, heat-exchange fins
Plate	>6 mm	Thicker plate requires more work for same hardness	O, H14, H16	Less common; used where higher stiffness and conductivity needed
Extrusion	Wall thickness varies	Extrusions can be supplied O or slightly strain-hardened	O, H12	Used for bus bars and profiles where high conductivity critical
Tube	Ø varies; wall 0.3–5 mm	Thin-walled tubing behaves like sheet in forming	O, H14	Heat exchanger tubing and cold-formed conduit
Bar/Rod	Diameter up to ~50 mm	Bars respond to drawing/rolling to increase strength	O, H16	Limited commercial use vs higher-strength alloys

Sheets and foils are the dominant product forms for 1085 due to its common uses in electrical conductors, foils, and heat exchangers; rolling to thin gauges is straightforward in the annealed condition. Extrusions and tubular products are produced when specific cross-sectional geometries are required for bus bars, fins, or conduit; these products typically leverage the alloy's conductivity and formability rather than structural capacity. Plate and bar are less common but available where large cross-sections with good conductivity and corrosion resistance are needed.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1085	USA	ASTM/AA designation for commercially pure Al (~99.85% Al)
EN AW	1085	Europe	EN numeric sometimes listed as "EN AW-1085" equivalent
JIS	A1085	Japan	JIS group equivalent for extra high-purity wrought Al
GB/T	Al99.85	China	Chinese standard often lists by nominal purity, Al≥99.85

Equivalent grades across standards primarily reflect the same high-purity chemistry and similar mechanical behavior; differences arise in impurity tolerances, certification test requirements and permitted trace elements for each standard body. Buyers should consult specific material specifications and mill certificates because allowable maxima for elements such as Fe and Si and the defined mechanical test methods may differ slightly between standards, affecting suitability for tightly specified electrical or corrosion-sensitive applications.

Corrosion Resistance

1085 demonstrates excellent general atmospheric corrosion resistance because of rapid formation of a thin, adherent aluminium oxide film that inhibits further attack. In marine environments the alloy performs acceptably in bulk and is commonly used for non-structural and moderately loaded components; periodic freshwater rinsing and coatings are used to mitigate chloride-induced pitting on exposed edges or machined surfaces. The low alloy content and absence of significant copper or zinc reduces susceptibility to localized corrosion compared with certain higher-strength alloys.

Stress corrosion cracking (SCC) susceptibility is low for 1085 when compared with high-strength Al-Zn-Mg or certain Cu-containing alloys, due in part to low residual tensile strengths and high ductility. Nevertheless, galvanic considerations are important: aluminium is anodic relative to most stainless steels and copper, so in assemblies with dissimilar metals, insulating layers or sacrificial design must be used to avoid accelerated corrosion where electrolyte continuity exists. Compared with 5xxx (Al-Mg) or 6xxx (Al-Mg-Si) families, 1085 trades lower structural strength for improved uniform corrosion behavior and better conductivity in electrical applications.

Fabrication Properties

Weldability

1085 is highly weldable by conventional fusion methods including TIG and MIG; the low alloying content limits hot-cracking tendencies. Recommended filler metals for structural or electrical joint integrity typically include commercially pure aluminium fillers (ER1100/ER1050 family) or Al-Si fillers (ER4043) when fluidity and reduced porosity are desired. Weld heat-affected zones do not benefit from precipitation hardening, so joint design and subsequent cold working determine final mechanical performance; care with oxide removal and gas shielding is critical to maintain low hydrogen pickup and porosity.

Machinability

Machining of 1085 is moderate to challenging due to its ductile, gummy nature compared with free‑cutting alloys. Tool materials of choice are sharp carbide or ceramic tooling with positive rake and high coolant application to evacuate chips and prevent smearing. Cutting speeds are often conservative relative to aluminium alloys containing silicon because 1085 lacks hard second‑phase particles that aid chip segmentation; feeds and depths of cut are adjusted to produce continuous chips and avoid work hardening at the cut face.

Formability

Formability is one of the principal strengths of 1085; in the O temper the alloy is excellent for deep drawing, bending, and spinning operations with tight bend radii possible. Typical minimum inside bend radii in O temper can approach 0.25–0.5× material thickness depending on tooling and surface condition, whereas H16/H18 tempers require larger radii or localized anneal. Cold work increases strength but reduces formability, so production forming is commonly done in annealed state with strain-hardening applied if required to meet end-use strength targets.

Heat Treatment Behavior

Because 1085 is essentially pure aluminium, it is not responsive to classic solution-treatment and artificial aging cycles used in heat‑treatable alloys. There is no practical T‑temper route to increase strength via precipitation hardening. Strength adjustments are achieved by work hardening (cold rolling, drawing, stretching) and by annealing to restore ductility. Full annealing (O) is accomplished by heating to temperatures typically in the 350–415 °C range depending on part geometry and then controlled cooling to produce maximum softness and ductility.

T temper transitions are not applicable; instead, manufacturers specify H tempers which define the amount and method of cold work and any stabilization treatment. Annealing cycles are used in production to remove work hardening prior to further forming or finishing; tight process control is required to prevent grain growth that can affect surface finish, especially for foil and thin-sheet applications.

High-Temperature Performance

1085 loses mechanical strength rapidly as temperature increases above ambient; significant reductions in yield and tensile strength occur above approximately 150–200 °C, making it unsuitable for high-temperature structural applications. Oxidation resistance remains good at moderate temperatures due to the formation of protective Al2O3, but prolonged exposure at elevated temperatures can cause grain growth and degrade mechanical and surface properties. In welded assemblies, the heat-affected zone does not gain strength and will soften only by localized annealing when exposed to high temperatures, which can influence load-bearing capacity in service.

For thermal management uses, 1085 maintains excellent conductivity at elevated temperatures relative to many alloys, but designers must consider creep and strength loss for sustained loads; practical continuous service temperatures for mechanical integrity are generally kept below 125–150 °C unless conservative design margins are applied.

Applications

Industry	Example Component	Why 1085 Is Used
Automotive	Thermal fins / heat exchanger fins	High thermal conductivity and formability for tight fin spacing
Marine	Architectural trim, conduits	Corrosion resistance and ease of fabrication in wet environments
Aerospace	Non-structural shrouds, EMI shields	High conductivity and low weight for shielding and thermal dissipation
Electronics	Bus bars, heat sinks, foils	Excellent electrical and thermal conductivity, easy forming
Packaging	Foil and flexible packaging	Purity and malleability for thin-gauge foil production

1085 is particularly well suited to components where conductivity and formability outweigh the need for high structural strength. The alloy’s combination of low density, high conductivity and excellent ductility enables efficient production of thin-gauge parts, fins and foil. Its predictable corrosion performance and weldability make it an economical choice for many service environments.

Selection Insights

Choose 1085 when electrical or thermal conductivity and deep-draw formability are primary design drivers and when only modest mechanical strength is required. The alloy offers better conductivity and slightly improved corrosion uniformity compared with 1100 but with similar forming behavior; it is selected when small gains in purity and conductivity are needed without moving to specialty alloys.

Compared with common work‑hardened alloys such as 3003 or 5052, 1085 trades lower structural strength for higher electrical conductivity and marginally better general corrosion resistance in some environments. Engineers select 1085 when conductivity or foil applications are prioritized and when strain-hardening (H tempers) can provide the needed strength without alloying additions.

When compared with heat-treatable alloys such as 6061 or 6063, 1085 is preferred for conductivity, forming and corrosion uniformity despite significantly lower peak strength. Use 1085 for thermal and electrical components, or where extreme formability is required; select 6xxx-series alloys when higher structural loads or specific strength-to-weight ratios are obligatory.

Closing Summary

Alloy 1085 remains a relevant material in modern engineering where very high aluminium purity, excellent electrical and thermal conductivities, and superior formability are required. Its predictable, work‑hardening based mechanical behavior and excellent corrosion resistance make it an economical and reliable choice for conductive, thermal-management, and thin-gauge formed components across multiple industries.