Aluminum 1100: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

1100 is part of the 1xxx series of aluminum alloys, classified as commercially pure aluminum with a minimum aluminum content of about 99%. The 1xxx series is defined by very low alloying additions and is recognized for its excellent chemical purity relative to other series such as 3xxx or 6xxx.

Major alloying elements in 1100 are present only as controlled impurities: silicon, iron, copper, manganese, magnesium, and zinc all appear at trace to tenths of a percent levels. Because the alloy contains no significant strengthening additions, its mechanical strengthening is achieved almost exclusively through work hardening (cold working) rather than precipitation heat treatment.

Key traits of 1100 include excellent formability, very good corrosion resistance in atmospheric and many chemical environments, and outstanding thermal and electrical conductivity compared with more heavily alloyed grades. Weldability is generally excellent in the annealed temper because the alloy is ductile and does not require post-weld heat treatment, but mechanical strength is low compared with work-hardened and heat-treatable alloys.

Typical industries that use 1100 are chemical processing, food handling, signage, architectural trim, electronics (heat sinks), and applications needing high formability and corrosion resistance at low cost. Engineers choose 1100 when maximum ductility, conductivity, and corrosion performance per unit cost are more important than achieving high static strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–40%)	Excellent	Excellent	Fully annealed commercial-purity condition for maximum ductility
H12	Moderate	Moderate (10–20%)	Very Good	Very Good	Partial strain hardening with limited ductility reduction
H14	Moderate-High	Low-Moderate (8–15%)	Good	Very Good	Common cold-worked temper balancing strength and formability
H16	High	Low (6–12%)	Fair-Good	Good	Heavier cold work for higher strength but reduced forming capability
H18	Very High	Low (4–10%)	Limited	Good	Near-maximum commercially achievable strength through cold working
H24	Moderate (stable)	Moderate	Good	Very Good	Strain-hardened and stabilized by partial anneal/passivation

Temper has a first-order effect on 1100 properties because the alloy is non-heat-treatable. Cold working increases yield and tensile strength while reducing elongation and forming range. Selecting the right H-temper is a trade-off between forming steps and final part strength; many fabricators choose O for deep drawing and H14/H16 for lightweight structural sheet components.

Chemical Composition

Element	% Range	Notes
Al	Balance (≥ 99.0%)	Principal constituent; typically >99% by weight in commercial 1100
Si	≤ 0.95	Common impurity; slightly reduces conductivity and improves castability in small amounts
Fe	≤ 0.95	Impurity that forms intermetallics affecting strength and surface finish
Mn	≤ 0.05	Minor impurity; little strengthening effect at these levels
Mg	≤ 0.05	Negligible in 1100; not a source of precipitation strengthening
Cu	≤ 0.05	Kept very low to preserve corrosion resistance and conductivity
Zn	≤ 0.10	Trace levels; higher Zn would reduce ductility and corrosion resistance
Ti	≤ 0.15	Often present from grain refiners; small additions improve microstructure control
Others	≤ 0.05 each, total ≤ 0.15	Trace elements present in commercial production limits

The essentially-pure aluminum matrix dominates performance: electrical and thermal conductivity scale inversely with the concentration of alloying impurities, while mechanical strength is strongly influenced by cold work and the presence of intermetallic particles composed of Si and Fe. Control of minor elements like Ti is used primarily for grain structure control during casting/rolling rather than bulk strengthening.

Mechanical Properties

Tensile behavior of 1100 is characteristic of a low-strength, highly ductile, face-centered cubic metal. In the annealed O temper the alloy exhibits low yield and ultimate strengths with elongations typically in the tens of percent, enabling extensive plastic deformation without fracturing. Cold working increases dislocation density and yields significant strength gains but at the expense of ductility and formability.

Yield and tensile strength depend strongly on temper and thickness; thinner gauges that are cold rolled can achieve higher strengths due to greater strain accumulation during processing. Hardness correlates with temper and is commonly used as a quick production control for work-hardened sheets; Brinell hardness values are low in O and increase predictably with H-tempers. Fatigue behavior is generally limited by the low static strength and surface condition; polishing and shot-peening can improve fatigue life but the alloy remains inferior to higher-strength series for cyclic-loaded parts.

Thickness has a practical effect because thicker plate is less readily cold worked to high hardness levels and may retain more of the annealed properties; designers must consider temper/thickness interactions when specifying strength or forming performance.

Property	O/Annealed	Key Temper (e.g., H14)	Notes
Tensile Strength (UTS)	~55–115 MPa (typical)	~110–180 MPa (typical)	Wide ranges depending on thickness and exact strain hardening; values are approximate
Yield Strength	~30–70 MPa (typical)	~90–150 MPa (typical)	Yield increases markedly with cold work; no precipitation hardening available
Elongation	~30–40%	~8–18%	Ductility falls as temper moves from O to higher H numbers
Hardness (Brinell)	~20–30 HB	~30–60 HB	Hardness scales with dislocation density from work hardening

Physical Properties

Property	Value	Notes
Density	2.71 g/cm³	Typical for aluminum and close to other low-alloy aluminum grades
Melting Range	~660 °C (solidus ≈ 657–660 °C)	As a nearly pure alloy, melting point is close to elemental Al
Thermal Conductivity	~200–230 W/m·K	High thermal conductivity; slightly lower than pure Al as impurities increase
Electrical Conductivity	~53–60 % IACS (typical)	Very good electrical conductivity for non-pure alloys; depends on impurity level
Specific Heat	~0.9 J/g·K	Typical value near that of pure aluminum at ambient temperatures
Thermal Expansion	~23–24 µm/m·K	Coefficient of thermal expansion typical of aluminum alloys

1100’s high thermal and electrical conductivity derive from the low concentration of alloying elements; these properties make it attractive for heat-spreading and conductor applications. The relatively high coefficient of thermal expansion must be accounted for in assemblies with dissimilar materials to avoid thermal-stress-induced distortion or sealing issues.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2 mm – 6 mm	Strength increases with cold rolling	O, H12, H14, H16	Widely available; used for deep drawing and decorative applications
Plate	>6 mm – 50+ mm	Lower achievable cold-worked strength in thick plate	O, H18	Thick stock is usually annealed; limited cold working post-rolling
Extrusion	Complex cross-sections up to large profiles	Strength depends on subsequent cold drawing/aging	O, H12, H14	Extrusions often used where formability and corrosion resistance matter
Tube	Diameters from small to large	Mechanical properties influenced by forming method	O, H14	Common in architectural and chemical handling tubing
Bar/Rod	Diameters up to 300 mm	Typically lower work-hardening unless cold-drawn	O, H16, H18	Used for machining or further forming into components

Processing routes influence the microstructure and mechanical behavior: rolling and cold drawing introduce strain hardening that raises strength, while annealing resets the microstructure for forming. Product selection should reflect the required forming sequence; sheet in O temper is preferred for deep drawing and spinning, while H-tempers are selected for parts that require added stiffness and strength without heat treatment.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1100	USA	Primary American Alloy designation for commercially pure Al
EN AW	1050A / 1100 (closest)	Europe	EN designations for commercially pure alloys overlap; 1050A is often the closest in practice
JIS	A1050 / A1100 (closest)	Japan	JIS has similar commercially pure categories; direct equivalence varies with impurity limits
GB/T	1060 / 1100 (similar)	China	Chinese standards offer comparable commercially pure grades with slightly different limits

There is no always-exact one-to-one mapping between standards because allowable impurity ceilings and classification conventions differ regionally. When substituting across standards, check specific chemical limits, temper definitions, and mechanical property guarantees rather than relying solely on nominal series numbers.

Corrosion Resistance

1100 exhibits excellent general-purpose corrosion resistance because the high aluminum content rapidly forms a thin, protective alumina (Al2O3) film. In atmospheric and mildly corrosive industrial environments 1100 performs well and typically resists pitting better than many higher-alloyed materials due to the absence of aggressive alloying elements.

In marine and chloride-containing environments 1100 resists uniform corrosion but is susceptible to localized attack where crevices and cathodic coupling occur; anodizing and protective coatings extend service life in severe saline exposures. Stress corrosion cracking is not a major concern for 1100 because it lacks the high-strength microstructures and alloying chemistry that promote SCC; nevertheless, high stresses in certain chloride-rich conditions can still initiate cracking.

Galvanic interactions are typical for aluminium: 1100 will be anodic when coupled to more noble metals such as stainless steels or copper, and designers must use insulating barriers or compatible fasteners to limit accelerated galvanic corrosion. Compared with other families, 1100 trades off some mechanical robustness for corrosion resistance and conductivity when contrasted with 5xxx or 6xxx series alloys that are stronger but may suffer different localized corrosion behaviors.

Fabrication Properties

Weldability

1100 is readily welded by TIG, MIG (GMAW), and resistance methods with very low risk of hot cracking provided good practices are followed. Common filler wires include ER1100, ER4043, and ER5356 depending on service requirements; ER1100 preserves conductivity and ductility while 4043/5356 can improve joint appearance and mechanical properties. Heat-affected zone (HAZ) softening is not a primary concern because the alloy does not gain properties from precipitation; however localized strength variations occur due to loss of cold work in weld-adjacent regions.

Machinability

Machinability of 1100 is rated as poor-to-moderate compared with free-machining aluminum alloys since it is soft and gummy, with a tendency to form long, continuous chips. Carbide tooling, high spindle speeds, light depths of cut, and generous lubrication/coolant help to control built-up edge and improve surface finish. Abrasive wear of tools is low but chip control and workholding require attention to avoid chatter and galling.

Formability

Formability in the O temper is excellent and permits extreme bending, deep drawing, and spinning operations. Minimum bend radii can often approach 1–2× material thickness in O temper for many sheet operations; H-tempers require larger radii and incremental forming. Cold forming increases strength via strain hardening and is the recommended method for parts where heat treatment is not an option.

Heat Treatment Behavior

As a non-heat-treatable alloy, 1100 does not respond to solution-and-aging cycles for precipitation strengthening. Attempts to apply T-type heat treatments will not produce the same gains seen in 6xxx or 7xxx series alloys. Typical thermal processing consists of annealing to restore ductility after cold working: full anneal (O) is achieved at temperatures that permit recrystallization and stress relief without melting.

Work hardening is the primary method of property enhancement; controlled sequences of cold work and stress relief or stabilization (H24, for example) are used to balance strength and dimensional stability. Thermal stabilization treatments should be selected carefully to avoid undesired grain growth or distortion, and parts that require mechanical property consistency after welding should be designed with expected HAZ softening in mind.

High-Temperature Performance

1100 loses strength rapidly with increasing temperature because the dislocation mechanisms and low alloy content offer little retention of strength above ambient ranges. For sustained mechanical loads designers commonly limit service temperatures to below about 100–150 °C to preserve mechanical integrity; short exposures up to 200 °C are tolerated but with measurable softening. Oxidation is limited because the protective alumina scale reforms quickly, but some embrittlement of surface oxides can affect forming operations at elevated temperatures.

Weld zone behavior and residual stress relaxation occur at elevated temperatures; elements used for galvanic protection can change anodic/cathodic relationships when temperatures produce microstructural changes. For high-temperature structural requirements select heat-treatable or high-temperature alloys rather than 1100.

Applications

Industry	Example Component	Why 1100 Is Used
Automotive	Interior trim, heat shields	Excellent formability and corrosion resistance for non-structural components
Marine	Architectural trim, chemical tanks	High corrosion resistance and ease of fabrication in corrosive environments
Aerospace	Fittings, chemical processing lines	Good combination of formability, corrosion resistance, and light weight for secondary structures
Electronics	Heat sinks, EMI shields	High thermal and electrical conductivity and good surface finish for thermal management
Food & Beverage	Countertops, tanks, utensils	Non-toxic oxide layer, cleanability, and corrosion resistance in many process fluids

1100’s combination of formability, conductivity, and corrosion resistance at low material cost makes it a go-to choice for many secondary structural and functional components. When the part does not require high static strength but does require forming or conductivity, 1100 often represents the most efficient material choice.

Selection Insights

Choose 1100 when maximum ductility, corrosion resistance, and thermal/electrical conductivity are primary project drivers and when mechanical loads are modest. For deep drawing, spinning, or complex formed parts 1100-O is usually the most economical and technically appropriate selection.

Compared with other commercially pure alloys (e.g., 1050), 1100 trades very slightly different impurity ceilings and may offer marginally different conductivity or surface finish; selection is often driven by available stock and supplier certification rather than performance jumps. Compared with common work-hardened alloys such as 3003 or 5052, 1100 generally has lower strength but better electrical/thermal conductivity and often superior formability; choose 3003/5052 when higher strength or strain hardening response is required. Compared with heat-treatable alloys like 6061 or 6063, 1100 is chosen when conductivity, formability, or corrosion resistance are more valuable than peak strength; 6061 remains preferable where higher structural strength or age-hardening is required.

Closing Summary

1100 remains a broadly used, low-cost aluminum alloy because it uniquely combines excellent formability, corrosion resistance, and high thermal and electrical conductivity in a commercially pure matrix. For parts that prioritize fabricability and service durability over peak strength, 1100 continues to be the pragmatic engineering choice.