Aluminum 1145: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 1145 belongs to the 1xxx series of aluminum alloys, which are designated as commercially pure aluminum grades with a minimum aluminum content substantially greater than 99%. The 1xxx series emphasizes high electrical and thermal conductivity together with excellent corrosion resistance and formability rather than high strength. The major alloying elements in 1145 are present only as residuals and trace additions: typical controlled impurities include silicon, iron and copper at very low concentrations; the aluminum content is normally specified ≥99.45% (balance).

Strengthening in 1145 is achieved almost exclusively through strain hardening (work-hardening) since the alloy is essentially non-heat-treatable; permanent increases in strength are accomplished by cold working (H tempers), while softening and recovery are achieved by annealing to the O temper. Key traits include excellent electrical and thermal conductivity, outstanding corrosion resistance in atmospheric and many chemical environments, excellent ductility and formability in annealed conditions, and very good weldability with limited concern for cracking associated with metallurgical phases. Typical industries using 1145 include electrical conductors and busbars, chemical and food processing, architectural trim, and heat-exchange components where conductivity and corrosion resistance are prioritized over peak mechanical strength.

Engineers select 1145 when high conductivity and corrosion resistance are critical and when forming operations or welding must be performed easily. It is chosen over higher-strength, alloyed aluminum grades when maximized conductivity, excellent surface finish, and deep draw/formability at low cost are required. Conversely, where high static strength or hardness is required, alloy families like the 5xxx or 6xxx series are preferred; 1145 occupies the design space favoring purity and serviceability rather than structural load-bearing performance.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–40%)	Excellent	Excellent	Fully annealed, maximum ductility for forming and drawing
H12	Low–Moderate	Moderate	Very good	Excellent	Light cold work, retains high formability
H14	Moderate	Moderate (10–25%)	Good	Excellent	Common cold-worked temper for moderate strength increases
H16	Moderate–High	Lower	Fair	Excellent	Higher cold work, reduced ductility, used for some structural applications
H18	High	Low (2–10%)	Limited	Excellent	Heavily cold-worked, maximum strain-hardened strength for 1xxx series
H24	Moderate	Moderate	Good	Excellent	Solution treated and partial re-aging or stabilized, used where some tensile recovery is desired

Cold-working tempers (H-series) are the only routine methods for increasing strength in 1145; T-temper designations are not applicable because 1145 is not age-hardenable. Annealing to O returns the microstructure to a low-strength, high-ductility state useful for deep drawing and spinning operations. The choice of H12–H18 allows designers to trade formability for increased yield and tensile strength while maintaining the base alloy’s high conductivity and corrosion performance.

Chemical Composition

Element	% Range	Notes
Al	≥99.45	Balance; primary constituent providing conductivity and corrosion resistance
Si	≤0.25	Residual; higher Si lowers ductility slightly and increases strength marginally
Fe	≤0.60	Common impurity; increases strength but can reduce conductivity and formability
Mn	≤0.03	Trace levels only; minimal effect in 1145
Mg	≤0.05	Typically very low; minimal contribution to strength or age hardening
Cu	≤0.05	Kept low to preserve corrosion resistance and conductivity
Zn	≤0.05	Controlled low level to limit effects on electrical properties
Cr	≤0.05	May be present as trace impurity; little effect at these concentrations
Ti	≤0.03	Often used in minute amounts for grain refinement during casting/processing
Others	≤0.10 total	Sum of other impurities; tightly controlled to maintain high purity

The composition of 1145 is dominated by aluminum with intentionally low concentrations of alloying elements and impurities. The low levels of Fe and Si are the principal contributors to any strengthening beyond pure aluminum, but they are kept minimal to preserve electrical and thermal conductivities and to maximize corrosion resistance. Trace additions (Ti, small Mn) are used primarily for metallurgical control such as grain refinement during casting and processing rather than to create strengthening phases.

Mechanical Properties

Tensile behavior of 1145 is characteristic of commercially pure aluminum: low to moderate tensile strength in annealed condition with very high ductility, and increased strength but reduced elongation after cold working. The alloy shows a fairly linear elastic region transitioning to plasticity with considerable uniform elongation in O temper; strain-hardened tempers reduce uniform elongation and increase yield ratios. Hardness is low in O condition and rises predictably with the degree of cold work; Brinell or Vickers values remain low compared with alloyed aluminum grades.

Yield and tensile values are highly dependent on temper and thickness; thin-gauge cold-worked sheet attains higher yields for a given temper than thick plate due to work-hardening and processing histories. Fatigue performance for 1145 is moderate and strongly influenced by surface condition and residual stresses; polished, defect-free surfaces and controlled forming steps give better life than rough-rolled finishes. Thickness effects are important during forming and welding: thicker sections retain more of the cold-worked strength, and thermal exposure in welding can locally soften cold-worked regions through recovery.

Property	O/Annealed	Key Temper (e.g., H14/H18)	Notes
Tensile Strength	~70–120 MPa (typical range)	~120–170 MPa (varies with cold work)	Values depend on sheet thickness, processing and exact temper
Yield Strength	~15–60 MPa	~80–140 MPa	Yield rises significantly with degree of cold work; low in annealed O
Elongation	~25–40%	~2–20%	Elongation decreases as temper moves from O to H18; gauge and prep matter
Hardness	~20–40 HB	~30–60 HB	Hardness increases with strain hardening; still low vs alloyed Al grades

Physical Properties

Property	Value	Notes
Density	2.71 g/cm³	Typical for high-purity aluminum, useful for lightweight design calculations
Melting Range	~655–660 °C	Narrow solidus-liquidus interval characteristic of nearly pure Al
Thermal Conductivity	~220–235 W/m·K	High conductivity; slightly lower than pure Al when trace impurities are present
Electrical Conductivity	~58–63 %IACS	Excellent electrical conductor among commercial aluminum alloys
Specific Heat	~0.90 J/g·K (900 J/kg·K)	Good heat capacity for thermal management applications
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Typical isotropic thermal expansion for aluminum metals

The high thermal and electrical conductivities are among the defining properties of 1145 and guide its selection for heat sinks, busbars and conductor applications. Density and specific heat are effectively identical to other high-purity aluminums and factor into thermal mass and transient thermal response calculations. Thermal expansion must be accommodated in multi-material assemblies because differential expansion between 1145 and common steels or composites can lead to stress concentrations.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Strength influenced by cold rolling; thinner gauges can be strain-hardened more uniformly	O, H12, H14	Widely used for deep drawing, foil conversion and heat-sink stamping
Plate	>6.0 mm	Lower uniform work-hardening due to thickness; may be delivered softer	O, H18	Used where thicker sections with good corrosion resistance are needed
Extrusion	Cross-sections up to several hundred mm²	Extruded properties depend on billet temper and subsequent drawing	O, H14	Limited alloying makes extrusion straightforward; complex profiles possible
Tube	Diameters from mm to several hundred mm wall thickness variable	Wall thickness and cold-work determine final strength	O, H14, H18	Used for conduits, heat-exchange tubing and low-pressure service
Bar/Rod	Ø 2–100 mm	Cold drawing can increase strength; isotropic properties in long lengths	O, H14	Used for conductor rods, pins and machined parts requiring high conductivity

Processing routes differ substantially between sheet/plate and extrusions. Sheet and plate are commonly produced by rolling with controlled annealing cycles to achieve target tempers, while extrusions begin with high-purity billets and are followed by straightening and possible light cold working. Applications exploit the excellent formability of O-temper sheet for deep drawing and the increased yield of H tempers for parts requiring dimensional stability after forming or light machining.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1145	USA	Aluminum Association designation for the alloy typically used in North America
EN AW	1145	Europe	Harmonized EN AW-1145 is used commonly in European specifications and suppliers
JIS	A1050 / A1145 (approx.)	Japan	JIS has grades for high-purity aluminum; direct mapping may be to the Al99.5 family
GB/T	Al99.45 / 1145	China	Chinese standards reference high-purity aluminum grades similar to 1145

Equivalences across standards are often close but not always identical because different bodies control maximum impurity limits and acceptable mechanical property test methods. In procurement and design, engineers should request the exact standard (AA, EN, JIS, GB/T) and review the mill certificate to confirm impurity limits, tempering definitions and permitted processing variations. For electrical or corrosion-critical components, small differences in permitted Fe or Si can influence performance and should be reconciled between suppliers.

Corrosion Resistance

1145 forms a thin, adherent oxide film that provides excellent atmospheric corrosion resistance in neutral and mildly corrosive environments. It resists uniform corrosion well and performs satisfactorily in many industrial atmospheres; however, chloride-rich marine environments increase susceptibility to localized pitting and crevice corrosion if protective coatings or design measures are not employed. The high purity and lack of active alloying elements reduce galvanic corrosion risk relative to more highly alloyed aluminum grades, but 1145 can still act as an anode when coupled to cathodic materials like stainless steel or copper in electrolyte exposure.

Stress corrosion cracking is rare in the 1xxx series because there are no precipitate-forming strengthening phases and because residual tensile strengths are relatively low compared with susceptible heat-treatable Al alloys. Nonetheless, welded and cold-worked zones should be evaluated for residual stresses and surface defects that can promote localized degradation under sustained tensile loading in aggressive solutions. Compared with 5xxx or 6xxx series alloys, 1145 trades higher conductivity and slightly better pure corrosion resistance for considerably lower mechanical strength; compared with pure copper, 1145 is much more corrosion-resistant in atmospheric and many aqueous environments while being far lighter.

Fabrication Properties

Weldability

1145 is easily welded by common fusion processes such as TIG and MIG because it contains no hardening precipitates that promote hot cracking. Welds typically exhibit good ductility and acceptable electrical continuity, although the heat-affected zone (HAZ) will experience recovery and softening of any prior work-hardened temper. For applications where electrical conductivity across the joint is important, use low-resistance joint designs and consider filler wires of high-purity aluminum or matching 1xxx-series filler alloys to minimize conductivity loss and galvanic potential differences.

Machinability

As a soft, ductile alloy, 1145 is generally easy to machine but can work-harden rapidly under severe cutting conditions. Machinability indices are lower than those of free-machining alloys; therefore, tooling choices favor sharp carbide or high-speed steel tools with positive rake angles, effective chip breaking strategies and controlled feed rates. Surface finish and dimensional accuracy are readily achievable with appropriate speeds—moderate spindle speeds, higher feeds, and careful control of tool engagement help avoid built-up edge and minimize chatter.

Formability

Formability in annealed O temper is excellent with very low springback, allowing tight bend radii and extensive deep drawing with low risk of cracking. Recommended minimum bend radii depend on gauge and temper but can be as small as one to two times material thickness in O temper for many geometries; cold-worked tempers require larger radii to avoid edge cracking. The alloy responds predictably to incremental forming operations and is well-suited to stamping, spinning, and hydroforming when starting in O or light H tempers.

Heat Treatment Behavior

1145 is classified as non-heat-treatable; significant strength changes via solution treatment and aging are not applicable. Thermal cycles such as annealing (furnace or batch anneal) are used to remove work hardening and recover ductility—typical anneal cycles may be in the range of 300–400 °C followed by controlled cooling to reach O temper. Because it lacks age-hardening elements, artificial aging (T-temper) will not produce strengthening precipitates; as a result, designers must rely on cold working for strength increases.

Work hardening through cold rolling, drawing or bending is the standard route to increase mechanical properties; temper transitions within the H-series are achieved by varying the degree of plastic deformation and by controlled annealing heat treatments to stabilize properties. Careful control of processing history is required to ensure consistent yield and tensile values because mechanical properties in 1145 are highly process-dependent rather than compositionally controlled.

High-Temperature Performance

At elevated temperatures, 1145 loses strength rapidly compared with alloyed aluminum grades; significant softening occurs above approximately 150–200 °C due to recovery and accelerated diffusion processes. Prolonged exposure to temperatures near the melting range (≥300 °C) will lead to significant loss of mechanical integrity and is outside typical service limits for structural use. Oxidation is minimal for aluminum at moderate temperatures due to the protective oxide, but scaling and increased surface roughness can occur in aggressive high-temperature oxidizing environments.

Weld heat-affected zones can be particularly susceptible to localized softening when 1145 is welded or thermally cycled; design should avoid relying on residual cold-worked strength in the immediate vicinity of welds. For thermal management or transient heat applications (heat sinks, busbars), 1145 remains useful up to moderate temperatures due to retained conductivity, but mechanical loading at elevated temperature must be carefully accounted for in design analyses.

Applications

Industry	Example Component	Why 1145 Is Used
Electrical	Busbars, conductor strips	High electrical conductivity and good weldability
Heat Transfer	Heat sinks, fins	High thermal conductivity and light weight
Chemical/Food Processing	Tanks, piping linings, trays	Excellent corrosion resistance and clean surface finish
Architecture	Trim, flashing, panels	Formability, finishability and corrosion resistance
Consumer/Appliances	Foil, cans, reflective elements	Deep drawability and surface quality

1145 is favored in components where conductivity, corrosion resistance and formability outweigh the need for high strength. Its role in electrical conductors and thermal management hardware is particularly prominent due to the combination of low density, excellent conductivity and ease of fabrication. The alloy’s simplicity of metallurgy yields predictable behavior across forming, joining and finishing operations which supports reliable production and long-term deployment.

Selection Insights

Choose 1145 when electrical and thermal conductivity, excellent corrosion resistance and maximum formability are the primary requirements and when the application tolerates lower structural strength. Use O-temper 1145 for severe forming operations and H-series tempers where some dimensional stability or higher yield is required after forming.

Compared with commercially pure 1100, 1145 typically offers slightly higher controlled purity and conductivity at a similar or modestly improved strength; designers accept small trade-offs in specific impurity limits for better electrical performance. Compared with work-hardened alloys such as 3003 or 5052, 1145 provides superior conductivity and comparable corrosion resistance but lower peak strength and less ability for structural loading; it is preferred where forming and conductivity are prioritized. Compared with heat-treatable alloys like 6061 or 6063, 1145 is chosen when conductivity, corrosion resistance and low cost are needed despite substantially lower achievable peak strength; 1145 remains attractive for non-structural electrical/thermal applications where aging response and high alloy strength are unnecessary.

Closing Summary

Alloy 1145 remains a highly relevant material for modern engineering tasks that demand high conductivity, outstanding corrosion resistance, and excellent formability at low cost. Its simple metallurgical character provides predictable fabrication behavior and long-term serviceability in electrical, thermal and chemically exposed applications where peak strength is not the primary design driver.