Aluminum 1070: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

1070 is a member of the 1xxx series of wrought aluminum alloys and is classified as commercially pure aluminum with a nominal aluminum content of 99.7% by mass. Its designation indicates extremely low concentrations of alloying elements, making it part of the pure, non-heat-treatable family that relies primarily on cold work for strength increases.

The major alloying constituents are trace amounts of iron and silicon with minute levels of copper, manganese, magnesium, zinc, chromium and titanium present as residuals or controlled impurities. The alloy is strengthened predominantly through work-hardening (strain hardening) rather than precipitation hardening, and annealing is used to restore ductility and recrystallize the microstructure.

Key traits of 1070 include top-tier electrical and thermal conductivity among structural aluminum grades, very good corrosion resistance in many environments, excellent formability in the annealed condition, and straightforward weldability. These characteristics make it attractive to industries such as electrical and power distribution, chemical processing, reflectors and lighting, architectural components, and certain thermal management applications where conductivity is prioritized over strength.

Engineers choose 1070 over higher-strength alloys when maximum conductivity, superior formability and corrosion resistance outweigh the need for elevated mechanical strength. It is selected where complex forming, brazing or joining of thin sections is required and where the service environment benefits from the stable oxide film and minimal galvanic activity relative to other alloy groups.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed recrystallized condition for maximum ductility
H12	Medium-Low	Moderate	Good	Excellent	Light strain-hardened, common for drawing and light forming
H14	Medium	Reduced	Good	Excellent	Half-hard temper with balanced strength and stretch formability
H16	Medium-High	Low-Moderate	Fair-Good	Excellent	Three-quarter hard, used for higher stiffness in thin sections
H18	High	Low	Limited	Excellent	Full hard, maximized strength from cold work, limited forming
H22/H24	Variable	Variable	Variable	Excellent	Stabilized tempers combining solution/strain and light anneal control

Temper has a primary effect on the strength/ductility balance for 1070 because the alloy is non-heat-treatable; increased cold work drives strength up while reducing elongation and formability. Selection of temper is therefore a direct trade-off between the required in-service mechanical stiffness and the amount of forming or drawing operations the part must undergo.

Weldability remains excellent across tempers because there are no strengthening precipitates to dissolve, but post-weld softening from local annealing of cold-worked regions can alter local mechanical performance and must be accounted for in design and processing.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.20	Primary residual impurity; controlled to limit strength and maintain conductivity
Fe	≤ 0.40	Common impurity that forms intermetallics and affects mechanical properties
Mn	≤ 0.03	Typically very low; can slightly influence grain structure if present
Mg	≤ 0.03	Minimal; low levels do not produce precipitation hardening in 1070
Cu	≤ 0.05	Kept very low to preserve corrosion resistance and conductivity
Zn	≤ 0.03	Residual level; higher Zn would be used in different alloy families
Cr	≤ 0.03	Trace amounts can influence recrystallization behavior at very low levels
Ti	≤ 0.03	Often present as a grain refiner in small intentional additions
Others (each)	≤ 0.05	Combined other elements kept low to preserve high Al purity; Al balance

Aluminum is the balance of the composition (≈99.7%), and the low total of alloying elements is the defining characteristic of 1070. Trace elements and impurities influence grain size, forming behavior and the stability of the natural oxide film; tight control of these elements ensures high conductivity and predictable cold-work response.

Mechanical Properties

Tensile behavior for 1070 is characterized by low yield strength and moderate ultimate tensile strength in the annealed condition, with significant increases possible through cold working. Yield strength is relatively low compared with alloyed series, so design must accommodate higher deformations before yield, and elongation in the annealed state is typically high which benefits forming and deep drawing operations.

Hardness in annealed 1070 is low (soft, compliant) and increases progressively with cold work; hardness correlates with tensile values and is useful for process control during coining, bending and stretch-forming operations. Fatigue performance is influenced by surface condition and cold work: surface defects and notches dominate fatigue life in thin gauge products, while cold work can improve fatigue strength at the expense of ductility.

Thickness has a substantial effect on mechanical metrics because gauge-dependent grain structures and processing histories alter yield and elongation; thin sheets often show better formability and elongation values, whereas thicker plates may retain lower elongation and slightly higher strength depending on rolling schedules.

Property	O/Annealed	Key Temper (e.g., H14/H16)	Notes
Tensile Strength	~60–95 MPa	~110–180 MPa	Strong dependence on cold work and thickness; ranges are typical for rolled material
Yield Strength	~20–45 MPa	~80–160 MPa	0.2% offset yield varies with temper and prior deformation history
Elongation	~15–35%	~1–10%	Annealed condition provides deep drawability; cold working reduces ductility markedly
Hardness (HB)	~15–35 HB	~30–65 HB	Brinell hardness approximate; cold work increases hardness in proportion to strength gains

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for aluminum alloys, useful for mass and stiffness calculations
Melting Range	660–660.5 °C	Solidus-liquidus range is narrow for high-purity aluminum
Thermal Conductivity	220–240 W/(m·K)	Excellent thermal conductor; among the best of structural aluminum alloys
Electrical Conductivity	~60–64 % IACS	High electrical conductivity for distribution and busbar applications
Specific Heat	~0.90 J/(g·K)	High specific heat supports heat-sink and thermal buffering uses
Thermal Expansion	~23.6 µm/(m·K)	Typical coefficient for aluminum; important for thermal mismatch design

The combination of low density and high thermal/electrical conductivities makes 1070 valuable where mass, heat transfer, or current carrying capacity dominate material selection. Thermal expansion and conductivity data are critical during joined assemblies to manage CTE mismatch and thermal cycling stresses in electronics and architectural applications.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Strength increases with cold rolling	O, H12, H14, H16	Widely used for reflectors, packaging, facing panels
Plate	>6.0 mm	Limited; heavy-gauge plates are less common	O, H18	Available but less typical due to low alloy strength
Extrusion	Profiles up to large cross-sections	Strength tied to subsequent cold work	O, H14	Extruded shapes for busbars, frame components, and heat sinks
Tube	Thin- to thick-walled tubes	Cold work and drawing control mechanicals	O, H14	Used in chemical and architectural systems, easy to weld/braze
Bar/Rod	Diameters mm to large	Increased by cold drawing	O, H12/H14	Conductive rods, fastener stock, and specialty formed parts

Sheet and thin-gauge products are the most common product forms of 1070, optimized for forming and thermal/electrical applications; heavy plate is less frequent because higher-strength alloys are usually preferred for structural load-bearing. Extrusion and bar forms are used when profile geometry and conductivity are required, and their mechanical properties are primarily established later through cold working and temper selection.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1070	USA	Designation under Aluminum Association system for commercially pure Al
EN AW	1070	Europe	EN AW-1070 corresponds to similar compositional limits in European standards
JIS	A1070	Japan	Japanese Industrial Standard grade aligning with commercial-purity aluminum
GB/T	1070	China	Chinese standard grade with comparable impurity limits and applications

Equivalency tables reflect broadly similar chemical limits but can differ in maximum impurity concentrations, permitted trace elements, and specified mechanical property testing methods. These subtle differences influence procurement and quality control, and for critical electrical or formability applications engineers should verify certificate test data against the applicable regional standard.

Corrosion Resistance

1070 exhibits excellent general atmospheric corrosion resistance because of the continuous, tenacious aluminum oxide film that rapidly forms on exposure to air. In neutral and mildly corrosive industrial environments the alloy performs well, and the lack of aggressive alloying elements reduces susceptibility to galvanic-driven localized corrosion in many assemblies.

In marine environments 1070 shows reasonable resistance, but chloride-induced pitting can occur on contaminated surfaces or crevices; proper surface cleaning, protective coatings or anodizing are common mitigations for long-term offshore use. Stress corrosion cracking is not a significant concern for 1070 compared with high-strength heat-treatable aluminum alloys because of its low strength and absence of precipitate-hardened phases that can embrittle under tensile stress and corrosive environments.

Galvanic interactions must still be considered when 1070 is paired with nobler metals such as copper or stainless steel; although it is less active than zinc, when used as a conductor in contact with dissimilar metals, insulating layers, coatings or sacrificial protection should be used as needed. Compared with 3xxx and 5xxx series alloys 1070 often demonstrates better electrical and thermal properties but can be similar or slightly superior in corrosive resistance due to its high purity and stable oxide film.

Fabrication Properties

Weldability
1070 is readily welded by common fusion processes such as TIG and MIG because there are no hardening precipitates to dissolve during the thermal cycle, and weld metal properties are dominated by filler selection and fusion practices. Common filler wires include high-purity aluminum fillers (ER1100) or aluminum-silicon (ER4043) for improved fluidity; ER5356 (Al-Mg) is used when enhanced weld strength is necessary, though matching filler chemistry affects conductivity and corrosion behavior.

Hot-cracking risk is low for homogeneous, clean 1070 but can increase with contamination, improper joint design or aggressive travel speeds; control of heat input and filler metallurgy mitigates porosity and cracking. The heat-affected zone will typically anneal cold-worked regions, producing local softening and necessitating consideration of post-weld mechanical property gradients in design.

Machinability
Machining of 1070 is straightforward but requires attention to high ductility and tendency for the material to form long, continuous chips that can entangle tooling and workpieces. Recommended tooling includes sharp carbide or high-speed steel cutters with positive rake for chip control, moderate to high cutting speeds and ample coolant to avoid built-up edge and smearing on the surface. Machinability index is generally better than many alloyed aluminum grades but less than free-machining modified alloys; processes such as peck drilling and chip breakers are commonly applied.

Tool wear rates are low compared with steels, but surface finish and dimensional control demand rigid setups due to the material's softness and tendency to deform ahead of the cutting edge.

Formability
Formability is one of the strongest attributes of 1070, especially in the O temper where deep drawing, stretch forming and significant bending radii are achievable without fracture. Recommended minimum bend radii are typically small multiples of thickness in annealed sheet (e.g., 0.5–1× thickness for air bending in O), while half- and three-quarter hard tempers require larger radii and careful springback control. Cold work increases strength rapidly but reduces the allowable forming strain, so process planners usually form in O followed by light strain-hardening if higher stiffness is required in-service.

Heat Treatment Behavior

As a member of the commercially pure 1xxx series, 1070 is non-heat-treatable and does not respond to solution treatment or age hardening in the way Al-Mg-Si or Al-Cu alloys do. Strength is introduced and controlled by plastic deformation (work hardening) during processing; the various H tempers reflect the degree of strain hardening and any subsequent stabilization anneals.

Annealing or full softening (temper O) is achieved by heating to temperatures sufficient to recrystallize the structure and dissolve deformation-induced dislocation networks, typically followed by controlled cooling. Because there are no strengthening precipitates, there is no artificial aging or T6-like sequence; thermal exposure primarily results in softening and loss of cold-worked strength rather than the development of new strengthening mechanisms.

High-Temperature Performance

1070 retains moderate strength at slightly elevated temperatures but experiences significant softening above approximately 150–200 °C as recovery and recrystallization processes reduce dislocation density. For sustained service at higher temperatures, alloys specifically designed for elevated temperature use or mechanically stabilized designs are preferred, since 1070 lacks precipitate-strengthening mechanisms to maintain strength.

Oxidation resistance is generally good due to the stable oxide film on aluminum, but creep resistance is poor relative to alloyed aluminum and most engineering metals, limiting 1070 to low- to moderate-temperature applications where thermal conductivity and low density are the primary requirements. Welded joints in service at elevated temperatures should be evaluated for HAZ softening and changes in mechanical performance over time.

Applications

Industry	Example Component	Why 1070 Is Used
Electrical / Power	Busbars, conductor strips	High electrical conductivity and formability for complex shapes
Thermal Management / Electronics	Heat sinks, thermal spreaders	Excellent thermal conductivity and low weight for cooling
Lighting / Reflectors	Lamp reflectors, mirror substrates	High reflectivity, ease of polishing and forming
Chemical Processing	Tanks, piping liners	Corrosion resistance and easy fabrication for low-pressure systems
Architecture	Cladding, decorative panels	Formability, surface finish, and corrosion resistance

1070 is selected in these applications because its combination of high conductivity, excellent formability and corrosion resistance outweighs its low intrinsic strength for many component classes. Designers exploit its ability to be formed into thin, intricate shapes while maintaining consistent thermal and electrical performance.

Selection Insights

Select 1070 when electrical or thermal conductivity, excellent formability and superior corrosion resistance are higher priorities than yield strength or structural stiffness. Use the annealed O temper for deep drawing and complex shapes, and choose a light H temper when modest increases in strength are needed without sacrificing weldability.

Compared with commercially pure aluminum such as 1100, 1070 typically offers slightly higher nominal purity and conductivity at a comparable or slightly improved formability profile while trading off minimal gains in strength. Against work-hardened alloys such as 3003 or 5052, 1070 provides higher electrical and thermal conductivity and comparable corrosion resistance, but lower peak strength; it is chosen when conductivity is more critical than mechanical toughness.

When compared with heat-treatable alloys like 6061 or 6063, 1070 is selected for applications demanding higher conductivity and easier forming despite having substantially lower peak strength; 1070 is preferred in thermal or electrical components where the material is not required to carry heavy structural loads.

Closing Summary

1070 remains a relevant engineering aluminum because it uniquely balances high electrical and thermal conductivities with exceptional formability and corrosion resistance, making it the material of choice for non-structural components where these properties dominate design priorities.