Aluminum A1100: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A1100 is a 1000-series aluminum alloy, classified as commercially pure aluminum with minimum aluminum content typically around 99.0%. It belongs to the "11xx" family characterized by very low alloying content and minimal intentional additions beyond trace elements.

The major alloying elements are present only in small quantities and include silicon, iron, copper, manganese, magnesium, zinc, chromium, and titanium as residuals. These trace additions influence impurity control, grain structure, and mechanical consistency without turning the material into a heat-treatable alloy.

A1100 is a non-heat-treatable alloy that derives strength almost entirely from work hardening (cold working) and selected thermal annealing operations. Key traits are high electrical and thermal conductivity, excellent formability and corrosion resistance, and generally low mechanical strength compared with alloyed grades.

Typical industries that use A1100 include chemical process equipment, electrical and electronics (busbars, foils, and heat sinks), reflectors and architectural elements, packaging and food contact applications, and general sheet metal fabrication. Engineers choose A1100 when maximum ductility, surface finish, conductivity, and corrosion resistance are required while sacrificing peak strength and stiffness compared to 3xxx, 5xxx, or 6xxx alloys.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, maximum ductility
H12	Low-Mid	High-Mid	Very Good	Excellent	Quarter-hard, modest strength increase
H14	Mid	Moderate	Good	Excellent	Half-hard, common for moderate forming
H16	Mid-High	Moderate-Low	Fair	Excellent	Three-quarter hard, increased strength
H18	High	Low	Limited	Excellent	Full-hard, highest as-rolled strength
H22/H24	Low-Mid	Good	Very Good	Excellent	Strain-hardened then stabilized; retains formability

Temper selection for A1100 is dominated by strain-hardening levels rather than precipitation treatments because the alloy is not age-hardenable. Annealed O-temper offers the best formability and highest ductility for deep drawing and spinning operations. Work-hardened (H‑series) tempers trade ductility for strength and are chosen when forming is limited or when additional stiffness is required without resorting to alloyed materials.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.25	Usually present as residual; minor effect on castability
Fe	≤ 0.95	Main impurity; affects strength and surface appearance
Mn	≤ 0.05	Minimal; negligible strengthening
Mg	≤ 0.05	Very low; no significant solid-solution strengthening
Cu	≤ 0.05	Kept low to preserve corrosion resistance and conductivity
Zn	≤ 0.10	Residual; limited effect on mechanical properties
Cr	≤ 0.05	Trace amounts only; used to control grain structure
Ti	≤ 0.03	Grain refiner in cast and wrought processing
Others	≤ 0.15 total	Other residuals kept low to meet purity spec

A1100’s performance is dominated by its high aluminum fraction; trace impurities and minor intentional additions are controlled to preserve electrical and thermal conductivity and corrosion resistance. Iron is the principal residual that can influence anisotropy and surface finish, while trace titanium is important for grain refinement during casting and primary processing.

Mechanical Properties

Tensile behavior of A1100 is characterized by relatively low ultimate tensile strength and very good elongation in annealed condition. Yield strength is low in the O temper and increases proportionally with cold work in H tempers; the alloy does not display age hardening response. Elongation in O temper is high and falls off as the H-number increases, making H18 or full-hard unsuitable for deep drawing but appropriate for stiff components.

Hardness follows the same trend as tensile properties and correlates closely with cold-work level; Rockwell and Vickers numbers are modest in O temper and rise with H tempers. Fatigue performance is typical of low-strength aluminum alloys: fatigue limit is not sharply defined but fatigue endurance increases with surface finish, cold working, and reduction of stress concentrators. Thickness has a strong effect on mechanical values; thinner gauges are easier to cold work and can show higher apparent strength after rolling and cut-edge strain hardening.

Property	O/Annealed	Key Temper (H14 / H18)	Notes
Tensile Strength	~65–110 MPa	~110–180 MPa	Wide range depending on temper and thickness; H18 approaches upper values
Yield Strength	~10–35 MPa	~40–150 MPa	Yield increases markedly with work hardening; O-temper yield is very low
Elongation	~35–45%	~3–20%	High ductility in O; reduced in harder tempers depending on strain level
Hardness	~20–35 HB	~40–60 HB	Hardness rises with cold work; values depend on measurement scale and tempers

Physical Properties

Property	Value	Notes
Density	2.71 g/cm³	Typical for commercially pure aluminum
Melting Range	~660 °C (solidus/liquidus near 660 °C)	Behaves like near-pure aluminum; narrow melting interval
Thermal Conductivity	~220–235 W/m·K	High among structural metals; decreases slightly with impurity content
Electrical Conductivity	~45–65 % IACS	High conductivity; depends on impurity level and cold work
Specific Heat	~0.897 J/g·K (897 J/kg·K)	Typical specific heat at ambient temperature
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Moderate thermal expansion for metal design

High thermal and electrical conductivities make A1100 attractive for thermal management and conductor applications where formability is required. The modest density combined with excellent thermal diffusivity provides a favorable strength-to-weight trade-off for non-structural components. Thermal expansion must be considered in assemblies with dissimilar materials to avoid stress build-up during temperature cycling.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Low to medium after cold work	O, H14, H16, H18	Widely used for cladding, reflectors, and general fabrication
Plate	>6.0 mm	Low; difficult to harden by cold work at large thickness	O, H22	Used less commonly; machining and forming limited
Extrusion	Wall thicknesses variable	Low; extrusions can be strain-hardened	O, H12/H14	Limited compared with 6xxx alloys; used when purity and conductivity are priorities
Tube	Thin to medium gauge	Low; can be welded and drawn	O, H14	Common for heat exchanger fins and conduits
Bar/Rod	Diameters small to medium	Low; machinability is fair	O, H14	Used for rods and pins where corrosion resistance and conductivity matter

Sheets and foils are the most common forms for A1100, especially in packaging, cladding, and heat transfer applications because rolling produces excellent surface finish and thin gauges. Extrusions and bars are produced when the alloy’s conductivity and corrosion resistance are advantageous, but for high-strength structural extrusions other alloys like 6061 or 6063 are preferred. Plate and thick sections are rarely specified when strength is a design driver due to low yield.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A1100	USA	Primary designation for commercially pure 99% Al
EN AW	1100 / 1050A*	Europe	EN equivalents are approximate; AW-1050A and AW-1100 are often used interchangeably in practice
JIS	A1050 / A1100*	Japan	JIS uses A1050 and A1100 families for high-purity aluminum; chemical compositions overlap
GB/T	1100	China	GB/T designations align closely with AA A1100 in composition and intended use

Equivalency between standards is approximate because different regions set slightly different impurity limits and allowable minor elements. When cross-referencing, engineers should verify actual chemical spec sheets and mechanical property tables rather than relying solely on grade names. For critical electrical, thermal, or food-contact applications, request mill certificates to confirm compositional and temper details.

Corrosion Resistance

A1100 exhibits excellent general atmospheric corrosion resistance because it forms a self-healing oxide film that protects the surface. It resists many chemical environments and is commonly used in chemical process equipment and food contact applications for this reason. In marine environments A1100 performs reasonably well in atmospheric exposure but is less resistant than higher-magnesium alloys like 5xxx series in seawater immersion; localized pitting can be an issue if chloride concentrations are high.

The alloy has low susceptibility to stress corrosion cracking due to low strength levels and absence of high-strength microstructural phases that promote SCC. Galvanic interactions must be managed: A1100 is anodic relative to many stainless steels and copper alloys and will corrode preferentially when electrically coupled in an electrolyte. Designers often use coatings, isolation materials, or sacrificial anodes to mitigate galvanic attack in dissimilar-metal assemblies.

Fabrication Properties

Weldability

A1100 welds exceptionally well using common processes such as TIG (GTAW), MIG (GMAW), and resistance welding because of its high purity and low alloy content. Recommended filler alloys include 1100, 4043, or 5356 depending on joint requirements and service conditions; filler choice affects post-weld corrosion resistance and ductility. Hot cracking is rare in A1100 but weld HAZ softening is not a concern because the alloy is not heat-treatable; joints generally retain the ductile behavior of the base metal.

Machinability

Machinability of A1100 is rated as fair to good; the material’s low strength reduces cutting forces but its high ductility can produce long, continuous chips that need control. Carbide tooling and sharp geometry are preferred for interrupted cuts, while high-speed steel can be used for light work. Typical practice is to use moderate cutting speeds, positive rake angles, and chip-breakers or pecking strategies to avoid built-up edge and ensure dimensional stability.

Formability

A1100 is among the most formable aluminum alloys, particularly in O temper where deep drawing, spinning, and complex bending are routine. Minimum bend radii can be very small in annealed sheet; typical rule of thumb for O-temper sheet is an inside bend radius equal to 0.5–1.0 times the material thickness for many processes. Cold-worked H tempers have reduced elongation and require larger bend radii or incremental forming strategies; warm forming and intermediate anneals are used to restore ductility in complex fabrication sequences.

Heat Treatment Behavior

A1100 is non-heat-treatable; it does not respond to solution treatment and artificial aging to achieve precipitation strengthening. The principal strengthening mechanism available is plastic deformation (cold work) which increases dislocation density and yields elevated strength in H tempers. Annealing (O temper) softens the alloy by driving recovery and recrystallization to restore ductility and relieve residual stresses from forming or welding.

Typical processing sequences involve anneal → cold work → stabilization (for some H2x tempers) rather than solutionizing or aging cycles. Stabilized H22/H24 tempers use a mild thermal treatment to reduce strain-aging effects and set dimensional stability without precipitate hardening. For applications requiring higher strength, selection of a strain-hardened temper or a shift to alloyed, heat-treatable materials is necessary.

High-Temperature Performance

A1100 experiences significant strength loss as temperature rises, with practical service limits generally below 150 °C for load-bearing applications. Above these temperatures recovery processes reduce the work-hardened strength and can lead to softening even without deliberate annealing. Oxidation in air is minimal compared with ferrous alloys due to the protective oxide, but prolonged high-temperature exposure can degrade surface finish and slightly reduce thermal and electrical conductivities.

Weld heat-affected zones do not suffer from precipitate dissolution as in age-hardenable alloys, but local softening from thermal exposure is possible if the region exceeds recrystallization thresholds. For applications with elevated temperature or cyclic thermal loads, designers must account for creep, dimensional drift, and loss of residual strength when relying on work-hardened conditions.

Applications

Industry	Example Component	Why A1100 Is Used
Automotive	Inner panels, reflectors	Excellent formability and surface finish for visible parts
Marine	Ducting, fittings	Good corrosion resistance in atmospheric marine exposures
Aerospace	Non-structural fittings, shrouds	High conductivity and corrosion resistance with low weight
Electronics	Heat sinks, busbars, foil	High thermal and electrical conductivity with good formability

A1100 remains a go-to alloy where electrical and thermal conductivity, surface finish, and formability outweigh the need for high structural strength. Its ease of fabrication and consistent performance across common forming and joining processes make it a cost-effective choice for many non-critical load-bearing components.

Selection Insights

Choose A1100 when maximum ductility, conductivity, and corrosion resistance are primary requirements and the design can tolerate low yield and tensile strengths. It is typically the go-to for foil, cladding, heat sinks, and chemically sensitive environments where alloying additions would be detrimental.

Compared with higher-purity commercial variants (e.g., 1050 or 1060), A1100 offers similar conductivity and formability but may contain slightly higher allowable impurities that can influence surface finish and mechanical consistency. Compared with work-hardened commercial alloys like 3003 or 5052, A1100 provides superior conductivity and occasionally better corrosion resistance at the expense of substantially lower strength and fatigue resistance. Compared with heat-treatable alloys such as 6061 or 6063, A1100 is selected when formability, cost, and conductivity matter more than elevated structural strength and when the component is non-critical for stiffness or high-load service.

Closing Summary

A1100 endures as a practical alloy where purity, ductility, formability, and conductivity are prioritized over peak mechanical properties. Its low-cost processing, predictable cold-work response, and broad compatibility with common fabrication techniques make it a durable choice for thermal, electrical, and corrosion-sensitive applications in modern engineering.