Aluminum 1199: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 1199 is a member of the 1xxx series of aluminum, classed among the commercially pure and ultra-high-purity aluminums. It is characterized by an aluminum balance typically above 99.9% (often specified as 99.99% Al for semiconductor- and electrical-grade material), with trace levels of Si, Fe, Cu, Mn, Mg, Zn and other elements present at parts-per-million to low hundred ppm levels.

Strength in 1199 is derived primarily from its purity and from cold work; it is a non-heat-treatable alloy where mechanical processing (work-hardening) and grain structure control set mechanical performance. Key traits include excellent electrical and thermal conductivity, superior corrosion resistance in many environments, exceptional formability in the annealed (O) condition, and very good weldability for thin gauges. Typical industries include electrical and electronics (busbars, conductors, foil), chemical and food processing (corrosion-sensitive equipment), aerospace and cryogenic applications where purity and conductivity matter, and specialty architectural elements.

Engineers select 1199 when electrical/thermal conductivity and corrosion performance are primary requirements while moderate mechanical strength suffices. It is chosen over stronger heat-treatable alloys when joining, forming, or electrical continuity are critical, and it is preferred over lower-purity 1xxx variants when marginal gains in conductivity or cleanliness are necessary for downstream processing or service in aggressive environments.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (35–50%)	Excellent	Excellent	Fully annealed, maximum ductility and conductivity
H12	Low-Medium	Medium-High (25–40%)	Very Good	Very Good	Light strain hardening, retains good formability
H14	Medium	Medium (15–30%)	Good	Good	Typical cold-worked commercial temper for increased strength
H16	Medium-High	Medium-Low (10–25%)	Fair	Good	Higher cold work, used for modest strength gains
H18	High (for 1xxx)	Lower (8–18%)	Limited	Fair	Heavily cold-worked, bending and forming limited
T5 / T6 / T651	Not typical / Not applicable	N/A	N/A	N/A	1199 is non-heat-treatable; artificial aging tempers are generally not used

Temper directly controls the trade-off between ductility and strength in 1199 because the alloy does not respond to precipitation hardening. Cold work increases yield and tensile strength by dislocation accumulation and work hardening while reducing elongation and forming ease. Selecting an intermediate temper (H12–H14) is common when some strengthening is required without severely compromising formability or conductivity.

Chemical Composition

Element	% Range	Notes
Si	≤0.005	Typical impurity; minimizes effects on conductivity and casting behavior
Fe	≤0.01	Iron is the dominant impurity in 1xxx alloys; kept very low to maintain conductivity
Mn	≤0.002	Kept minimal; higher levels would affect strength and corrosion resistance
Mg	≤0.005	Controlled to avoid unintended solid-solution strengthening
Cu	≤0.001	Copper is minimized to preserve corrosion resistance and conductivity
Zn	≤0.005	Low zinc avoids embrittlement and galvanic effects
Cr	≤0.001	Trace levels only; contributes little to strength
Ti	≤0.002	Used rarely as grain refiner in casting or extrusion variants
Others	≤0.01 (total)	Includes Ni, V, Bi, Pb, Sn; kept very low for purity-sensitive applications

The composition of 1199 emphasizes aluminum balance with extremely low impurity levels to maximize electrical and thermal conductivity and to reduce intermetallic precipitates that would reduce ductility or corrosion resistance. Trace elements at ppm levels can nevertheless alter grain structure, recrystallization behavior, and small shifts in mechanical properties, so chemical control is critical for specialty applications.

Mechanical Properties

In the annealed (O) condition, 1199 exhibits low yield and tensile strengths typical of high-purity aluminum, combined with very high elongation and excellent bendability. Tensile behavior is ductile with a shallow strain-hardening response; the stress–strain curve is dominated by long uniform elongation and low proof stress. Hardness values in the O temper are low and correlate with the low dislocation density and minimal precipitate content.

Cold working increases yield and tensile strength significantly relative to the O condition, but at the expense of elongation and formability. Fatigue performance is moderate: unnotched fatigue lives are reasonable because of the ductility, but surface defects, cold work level and thickness have strong influence. Thickness effects are seen primarily in fatigue and bend performance—thin gauges form easily and retain conductivity, while thicker sections can display slightly higher strength but reduced bendability.

Property	O/Annealed	Key Temper (e.g., H14)	Notes
Tensile Strength	30–65 MPa	80–140 MPa	Values vary with gauge and degree of cold work
Yield Strength	10–30 MPa	60–120 MPa	0.2% offset yield depends strongly on temper
Elongation	35–50%	10–30%	Annealed material highly ductile; cold work reduces uniform elongation
Hardness	15–30 HB	30–70 HB	Low hardness in O; rises with work hardening

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Same as other commercial aluminums, used for mass and stiffness calculations
Melting Range	660–660.5 °C	Narrow melting interval of pure Al; useful for soldering and brazing considerations
Thermal Conductivity	220–240 W/m·K	Very high—advantageous for heat-sinking and thermal management applications
Electrical Conductivity	~60–65 %IACS (~35–38 MS/m)	Among the highest of commercial alloys due to ultra-low impurity content
Specific Heat	~900 J/kg·K	Typical for aluminum, relevant for thermal mass calculations
Thermal Expansion	23.0–24.0 µm/m·K	Similar to other Al alloys; important for thermal strain and joint design

High purity in 1199 maximizes thermal and electrical transport properties and yields physical behavior very close to theoretical pure aluminum. These properties make 1199 particularly attractive for heat-sink, busbar, and cryogenic applications where thermal conduction and low density are critical. Designers must account for high thermal expansion when joining to lower-expansion materials to prevent thermal stress.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.1–6.0 mm	Low to medium (depends on temper)	O, H12, H14	Widely used for electrical strip, foil precursors, and formed panels
Plate	6–25 mm	Lower relative strength per thickness due to purity; limited large-plate availability	O	Specialized thicker sections are less common and used where purity matters
Extrusion	Wall thicknesses 0.8–12 mm	Strength depends on cold work; good ductility for complex profiles	O, H14	Grain control and surface finish important for electrical parts
Tube	OD 6–150 mm	Good collapse and forming resistance in O; cold-worked for added stiffness	O, H16	Used for fluid handling and specialty conductive tubing
Bar/Rod	Diameters 3–50 mm	Low-to-moderate strength; responds to cold drawing	O, H14	Used for machining into connectors, rivets and fasteners where conductivity is needed

Sheets and thin-gauge forms dominate commercial use of 1199 because the high-purity advantage is most valuable where conductivity, surface quality, and formability are required. Extrusions and bars are produced when complex shapes or machined components are needed, but tight chemistry control through processing is essential to maintain high conductivity and low inclusion content.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1199	USA	Designation for ultra-high-purity aluminum in the Aluminum Association system
EN AW	No direct equivalent	Europe	No exact EN AW counterpart; closest commercial-purity grades are EN AW-1050/1060
JIS	No direct equivalent	Japan	Closest comparative material is JIS A1050 or A1070 in terms of purity
GB/T	No direct equivalent	China	Chinese standards offer high-purity grades but direct one-to-one mapping is not common

There are typically no exact cross-references to 1199 in some international standards because 1199 targets specialty, ultra-high-purity chemistries and applications. In practice, designers use 1100, 1050, 1060 family grades as functional equivalents for general-purpose applications, but those grades usually permit higher impurity levels and slightly lower conductivity. When strict purity or documented elemental ceilings are required, specifying AA 1199 or a manufacturer-specific high-purity grade is necessary.

Corrosion Resistance

Alloy 1199 demonstrates excellent general atmospheric corrosion resistance owing to its high aluminum content and minimal alloying elements that might form active intermetallics. In most non-aggressive environments it forms a stable, protective alumina film that limits uniform corrosion rates and provides long service life with minimal maintenance. Surface finish, impurities and cold work can influence localized corrosion tendencies, so processing controls and surface treatments are important for critical applications.

In marine or chloride-containing environments 1199 outperforms many alloyed aluminum grades because of the low levels of copper and other elements that promote pitting or crevice corrosion. Nevertheless, in severe chloride exposure galvanic interactions with more noble metals (e.g., copper, stainless steel) must be considered; use of insulating barriers or sacrificial anodes is common practice. Stress-corrosion cracking is rare in 1199 due to the absence of significant solute atoms that promote SCC, but high tensile residual stresses from forming or welding should be managed to avoid unexpected failures.

Compared to 5xxx and 6xxx families, 1199 has superior general corrosion resistance and conductivity but lower mechanical strength. Compared to other 1xxx family alloys, 1199 often offers marginally improved behavior due to its tighter impurity control; this makes it attractive for chemical processing, sanitary and electrical applications where corrosion and contamination potential must be minimized.

Fabrication Properties

Weldability

1199 is readily welded by common fusion processes such as TIG and MIG because the alloy is essentially pure aluminum and presents low hot-cracking susceptibility in thin gauges. Filler choices include commercially pure aluminum fillers (e.g., Al 1100) for conductivity matching or 4043/5356 when improved mechanical properties are desired; selection depends on service requirements and post-weld conductivity acceptance. Care is required to control heat input to minimize grain growth and localized softening in the heat-affected zone; pre- and post-weld mechanical treatments are used when strength or formability must be preserved.

Machinability

As a very soft, ductile metal, 1199 machines easily but can be prone to built-up edge and poor surface finish if tooling and speeds are not optimized. High positive-rake carbide or ceramic tooling and sharp geometries reduce rubbing and promote continuous chip formation; use of appropriate lubricants or flood cooling aids chip evacuation and tool life. Machining parameters should favor higher feed rates and controlled spindle speeds to avoid smearing, and finishing passes benefit from light cuts to achieve low surface roughness and preserve conductivity.

Formability

1199 is highly formable in the annealed condition and can support aggressive forming operations such as deep drawing, roll forming and tight-radius bending that would fracture stronger alloys. Recommended minimum inside bend radii in the O condition are often in the range of 0.5–1.0× material thickness for mild operations, with larger radii recommended for thicker sections or complex draws. Cold-work response is predictable and controllable; intermediate tempers (H12–H14) allow incremental strength gains without fully sacrificing forming capability.

Heat Treatment Behavior

Because 1199 is essentially pure aluminum, it is non-heat-treatable in the precipitation-hardening sense. There is no beneficial age-hardening through solution treatment and artificial aging as seen in 2xxx, 6xxx or 7xxx series alloys. Thermal treatments are thus confined to annealing cycles: full anneal (O) at temperatures near 350–415 °C (followed by slow cooling depending on section) to relieve cold work and maximize ductility, and control of recrystallization to tune grain size.

Work hardening by cold deformation is the primary method to increase strength and modify properties. Repeated cycles of cold work followed by partial anneal or recovery treatments allow control of mechanical properties for stamping or forming sequences. For fabrication involving welding, localized annealing and post-weld mechanical operations can be used to restore ductility in the HAZ or to calibrate final temper.

High-Temperature Performance

1199 shows relatively rapid loss of mechanical strength as temperature increases above ambient because the alloying content that might stabilize strength at elevated temperature is minimal. Practical upper service temperatures are typically limited to about 150–200 °C for load-bearing applications; above these ranges significant softening and creep may occur. Oxidation is limited to the formation of a thin, protective alumina scale that prevents progressive surface degradation except in highly oxidizing molten or fuming environments.

Thermal stability of electrical and thermal conductivity remains acceptable to moderately elevated temperatures, but careful attention to thermal expansion mismatch and mechanical relaxation under sustained load is required for assemblies. The heat-affected zone adjacent to welds can exhibit grain coarsening and softening; design and fabrication procedures should minimize prolonged exposure to high temperature where mechanical performance is needed.

Applications

Industry	Example Component	Why 1199 Is Used
Electrical & Power	Busbars, connectors, foil	High electrical conductivity and good formability for stamped/bent parts
Electronics & Thermal Management	Heat sinks, thermal straps	Exceptional thermal conductivity combined with low density
Chemical / Food Processing	Corrosion-resistant tanks, liners	High purity and corrosion resistance reduce contamination risk
Aerospace / Cryogenics	Cryogenic vessels, fittings	Low impurity content and ductility at low temperatures
Architecture / Art	Decorative panels, formed facades	Excellent surface finish, formability, and corrosion resistance

1199 is selected where its combination of high conductivity, formability and corrosion resistance delivers functional benefits that outweigh its modest mechanical strength. It is often deployed in thin-gauge components and specialty parts where purity and transport properties are prioritized over structural load-carrying performance.

Selection Insights

For engineers choosing between 1199 and other aluminum options, consider the required balance of conductivity, formability and strength. Compared with commercially pure aluminum grades such as 1100, 1199 offers tighter impurity control and slightly higher conductivity and cleanliness, at comparable or slightly lower mechanical strength in certain processing routes. Compared with common work-hardened alloys like 3003 or 5052, 1199 trades off some strength for superior electrical and thermal conductivity and, in many environments, improved corrosion resistance; choose 1199 when conductivity or contamination sensitivity is decisive.

Against heat-treatable alloys such as 6061 or 6063, 1199 provides much higher conductivity and often better formability but lower peak strength. Use 1199 when joining quality, conductivity, or forming complexity outweigh the need for high, age-hardened strength. In procurement, weigh cost and availability—1199 is specialized and may carry a premium or lead time relative to more common 1xxx or 5xxx alloys, so reserve its use for applications that directly leverage its unique properties.

Closing Summary

Alloy 1199 remains relevant where ultra-high aluminum purity, excellent electrical and thermal conductivity, and superior corrosion resistance are required together with superior formability and weldability. Its role is complementary to stronger, alloyed aluminums: engineers choose 1199 when performance drivers favor transport properties, cleanliness and ductile forming over maximum structural strength.