Aluminum 443: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 443 is classified within the 4xxx series of aluminium alloys, a family dominated by silicon as the principal alloying element. The 4xxx series is typically characterized by moderate silicon contents that lower the melting range and improve wear and brazability; 443 follows this pattern while incorporating controlled additions of iron, manganese and trace elements to tune strength and processing behavior.

The major alloying elements in 443 are silicon (Si), iron (Fe) and small amounts of manganese (Mn), with minor additions of copper (Cu), magnesium (Mg), chromium (Cr) and titanium (Ti) used to refine grain structure and control strength. The alloy is principally non-heat-treatable and derives its usable strength from solid-solution effects and strain hardening introduced by cold working. Small microalloying additions and silicon-rich phases confer elevated stiffness and dimensional stability compared with near-pure aluminium.

Key traits of 443 include moderate to good strength for an aluminium alloy (higher than commercially pure grades), good thermal conductivity, favorable machinability and reasonable corrosion resistance in typical atmospheric environments. Weldability is generally good for common fusion processes but requires attention to filler selection to avoid local galvanic effects and porosity. Typical industries using 443 include automotive body panels and structural sections, marine fittings, consumer electronics enclosures and components where a balance of formability, weldability and higher strength than pure Al is required.

Engineers select 443 when a cost-effective, silicon-bearing aluminium is required that offers improved strength and thermal behavior over 1xxx and 3xxx family members, while being simpler to fabricate and more economical than high-strength heat-treatable alloys. Its lowered melting range and silicon content also make it attractive where brazing or localized melting processes are present, and where thermal conductivity plus dimensional stability during heating cycles is important.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–35%)	Excellent	Excellent	Fully annealed condition, best formability
H12	Low-Medium	Medium (10–18%)	Very Good	Very Good	Light strain hardened, retains reasonable ductility
H14	Medium	Lower (6–12%)	Good	Very Good	Moderate strain hardening for panel applications
H16	Medium-High	Low (4–10%)	Fair	Good	Heavier cold work for higher yield
H18	High	Low (2–6%)	Poor	Good	Heavily strain-hardened for maximum as-processed strength
T4 (if stabilized)	Low-Medium	Medium-High	Very Good	Good	Stress-relief / natural stabilization after forming

Temper has a primary influence on the balance between strength and ductility in 443; O temper gives maximum elongation and ease of forming while H-tempers trade ductility for yield and tensile strength via controlled cold work. For fabrication, selecting a temper is a function of the end part geometry and process flow: form in O or H12, then spring to a higher H-temper by cold working as required.

Chemical Composition

Element	% Range	Notes
Si	0.8 – 2.0	Primary alloying element; lowers melting point and forms silicon-rich phases
Fe	0.4 – 1.2	Impurity-stabilizing intermetallics; affects strength and toughness
Mn	0.05 – 0.6	Grain structure control; improves strength and corrosion resistance
Mg	0.02 – 0.20	Minor; can slightly increase strength via solid solution
Cu	0.01 – 0.20	Small additions for strength but reduces corrosion resistance if high
Zn	0.02 – 0.25	Trace; limited solid solution strengthening
Cr	0.01 – 0.15	Controls recrystallization and grain growth during processing
Ti	0.01 – 0.10	Grain refiner for cast or wrought products
Others (including balance Al)	Balance	Includes low-level residuals (Ni, V, Zr) depending on mill practice

The composition of 443 is tuned to keep silicon as the dominant alloying constituent while controlling iron and manganese to balance toughness, extrudability and precipitation behavior. Silicon provides wear resistance and thermal performance while iron and manganese form intermetallic phases that strengthen the alloy but can reduce ductility if present in excess. Trace elements such as chromium and titanium are intentionally kept low to refine grain size and stabilize properties during forming and welding.

Mechanical Properties

443 exhibits tensile behavior typical of non-heat-treatable silicon-bearing aluminium grades: a relatively linear elastic region followed by moderate plasticity and good energy absorption in annealed forms. Yield and ultimate tensile strength increase substantially with cold work; however, ductility and fracture toughness decrease commensurately. The alloy responds predictably to thickness-dependent forming strains, with thinner gauges achieving higher cold-work-induced strength because of strain localization.

Hardness trends track directly with temper and cold work. In annealed condition hardness is low, enabling easy machining and forming, while H18 or similar tempers deliver marked hardness increases useful for stiff components. Fatigue performance for 443 is adequate for moderate endurance applications; fatigue resistance is improved with proper surface finish and avoidance of aggressive notches or weld-induced discontinuities. Thickness effects are significant: thicker sections can retain slightly lower apparent strength in bending due to residual microstructural heterogeneity, and cooling rates during fabrication influence local precipitate distribution.

Property	O/Annealed	Key Temper (H14/H18)	Notes
Tensile Strength	80 – 130 MPa	180 – 260 MPa	Strength increases with cold work; values depend on exact Si content and working
Yield Strength	30 – 70 MPa	110 – 170 MPa	Yield rises markedly with strain-hardening; often the design-limiting value
Elongation	20 – 35%	2 – 12%	Ductility decreases as strength increases; annealed condition best for forming
Hardness (HB)	30 – 50	60 – 95	Brinell values approximate; hardness correlates with temper level

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical aluminium alloy density; excellent strength-to-weight ratio
Melting Range	~570 – 640 °C	Silicon lowers solidus compared with pure Al; range depends on Si fraction
Thermal Conductivity	120 – 160 W/m·K	Good thermal conduction for heat-sinking and thermal management
Electrical Conductivity	30 – 45 % IACS	Reduced from pure aluminium due to alloying; still reasonable for conductors
Specific Heat	~0.90 J/g·K	Near that of pure aluminium; useful for thermal mass calculations
Thermal Expansion	22 – 24 µm/m·K	Coefficient of thermal expansion typical for most Al alloys

443 combines relatively low density with good thermal conductivity, making it attractive where heat dissipation and weight control are both important. The reduced melting range aids localized joining and brazing but requires careful temperature control to prevent melting or segregation of silicon-rich phases. Electrical conductivity is compromised compared with high-purity aluminium but remains useful for many non-critical conductive applications.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3 – 6.0 mm	Sensitive to cold work; thin gauges gain strength quickly	O, H12, H14	Common for body panels and heat sinks; excellent formability in O
Plate	6 – 25 mm	Less cold-worked; retains annealed properties unless processed	O, H16	Used for structural components where thickness provides stiffness
Extrusion	Profiles up to 200 mm	Can be extruded then cold-drawn for higher strength	O, H14, H16	Good dimensional stability for rails and frames
Tube	Ø 6 – 150 mm	Wall thickness affects collapse strength and bending	O, H12, H14	Common in lightweight structural tubing and heat-exchanger cores
Bar/Rod	Ø 3 – 50 mm	Can be cold-worked to higher strength	O, H14, H18	Used for fasteners, shafts, and machined components

Form and section thickness significantly influence processing routes and final properties for 443. Sheets and thin extrusions are normally supplied annealed for forming and then work-hardened to target strength, while thicker plates are often specified in softer tempers to avoid cracking during forming. Extrusion practices require careful control of billet chemistry and thermal profile to prevent silicon segregation and to achieve consistent dimensional tolerances.

Equivalent Grades

Standard	Grade	Region	Notes
AA	443	USA	Primary numerical designation used commercially in North America
EN AW	No direct standard equivalent	Europe	No single EN AW number maps directly; nearest are AlSi-Mn family alloys
JIS	No direct equivalent	Japan	Regional variants available with similar Si/Fe/Mn balances
GB/T	No direct equivalent	China	Chinese standards may list closely related Al-Si wrought grades

There is no universal one-to-one equivalent to AA 443 across all international standards; instead, engineers should compare detailed chemistry and mechanical property tables when substituting grades. Regional mills sometimes produce proprietary 443 variants with slightly different impurity limits or processing histories, so specification of composition tolerances, tempers and process routes is critical when procuring international material.

Corrosion Resistance

In atmospheric environments 443 shows moderate corrosion resistance typical of silicon-bearing aluminium alloys, forming a protective aluminium oxide film that limits uniform corrosion. The presence of silicon and modest iron levels tends to reduce susceptibility to general corrosion compared with copper-bearing 2xxx alloys, but may lower performance relative to higher-magnesium 5xxx series in some environments.

Marine exposure is serviceable for 443 in unstressed components, but careful design is required where chloride attack and crevice corrosion are possible. Pitting resistance is not as high as 5xxx or clad 6xxx alloys specifically optimized for marine use; sacrificial protection, isolating coatings or cathodic design considerations are commonly applied for long service life.

Stress corrosion cracking (SCC) susceptibility is low compared with high-strength heat-treatable alloys, yet welded or highly cold-worked zones can exhibit localized degradation under tensile loading in aggressive environments. Galvanic interactions with cathodic metals (e.g., stainless steel or copper) must be managed by avoiding direct contact or isolating with coatings and sealants, since 443 will be anodic relative to many engineering metals. Overall, 443 offers a balanced package of corrosion resistance versus formability and cost, but is not chosen for highly aggressive chloride-dominated seawater structures without protective measures.

Fabrication Properties

Weldability

443 welds well with common fusion processes such as TIG and MIG when appropriate filler alloys are selected; silicon-bearing fillers matched to the base composition minimize hot-cracking and provide good bead appearance. Care must be taken to control weld heat input and interpass temperature because localized melting of silicon-rich phases and HAZ softening can occur, leading to reduced local strength. Pre- and post-weld treatments are rarely required for strength restoration, but stress relief and proper joint design help avoid distortion and porosity.

Machinability

Machinability of 443 is generally good compared with higher-strength aluminium alloys because of its moderate strength and silicon content which provides a predictable chip formation tendency. Carbide tooling at moderate speeds with rigid fixturing yields good surface finish; recommended feeds and speeds should be tuned to cutting diameter and depth to avoid built-up edge. Coolant use improves tool life and part temperature control; chip breaking aids are useful for long-turning operations due to ductile chip tendency in softer tempers.

Formability

Formability is excellent in annealed (O) condition, with tight bend radii achievable depending on gauge and tooling; recommended minimum inside bend radii are typically 1–2× the material thickness for moderate-strength tempers. The alloy responds well to common cold-forming operations including deep drawing and roll forming when in O or H12 tempers, with limited springback due to its silicon content. For severe forming, temporary annealing or warm-forming techniques reduce cracking risk and improve surface finish.

Heat Treatment Behavior

443 is effectively non-heat-treatable in the precipitation-hardening sense; bulk strengthening by T6-style artificial aging is not effective because silicon-dominated phases do not provide the same precipitate spectrum as Al-Mg-Si alloys. Attempts to apply solution treatment and aging cycles result primarily in modest microstructural coarsening rather than substantial increases in peak strength.

Work hardening and controlled annealing are the primary ways to tailor 443’s properties. Full anneal (O) recrystallizes the structure and returns maximum ductility, whereas partial anneals and controlled cold work give predictable increases in yield and tensile strength. Stabilizing treatments such as a low-temperature bake or natural aging (T4-like stabilization) are sometimes used to reduce dimensional change after forming but do not produce large strength gains.

Heat exposure can cause local softening through recovery and grain growth, so components that undergo subsequent thermal cycles (e.g., welding, localized brazing) should be assessed for property loss in the heat-affected zone. Where remedial strength is needed after thermal cycles, mechanical cold work or shot-peening may be employed rather than conventional precipitation hardening.

High-Temperature Performance

Like most aluminium alloys, 443 experiences significant strength loss as temperature rises above ambient; measurable reductions in yield occur by 100–150 °C and more substantial softening by 200–300 °C. Long-term exposure at elevated temperatures will promote creep and stress relaxation phenomena, limiting the alloy's use in sustained high-temperature load-bearing applications. Designers should assume conservative reduction factors for strength at temperature unless component testing under service conditions is undertaken.

Oxidation of aluminium alloys at elevated temperature is generally limited to surface oxide growth; 443 maintains a protective oxide layer but prolonged exposure in oxidizing atmospheres combined with mechanical loading can accelerate degradation. Thermal expansion should be accounted for in assemblies to avoid thermally induced stresses that could exacerbate fatigue or cracking at joints, especially in dissimilar metal assemblies where differential expansion is significant.

Welded regions and heat-affected zones are particularly susceptible to local property changes under high thermal exposures; grain coarsening and precipitate dissolution in these areas can lower fatigue endurance and yield strength. For intermittent elevated-temperature service, design allowances and periodic inspection are recommended.

Applications

Industry	Example Component	Why 443 Is Used
Automotive	Body panels, inner structural elements	Good formability in O temper, increased strength after cold working, cost-effective
Marine	Brackets, non-critical structural fittings	Reasonable corrosion resistance and good weldability for assembly
Aerospace (non-primary)	Interior fittings, housings	Favorable strength-to-weight and thermal stability for secondary structures
Electronics	Heat sinks, chassis	Thermal conductivity combined with good machinability
Consumer Goods	Appliance panels, trims	Balance of finishability, formability and cost

443 finds its niche in components that need a compromise between formability, thermal performance and higher strength than commercially pure aluminium. Its ease of fabrication and thermal conductivity make it a frequent choice for enclosures, heat-dissipating parts and formed structural panels where extreme strength is not the primary requirement.

Selection Insights

Select 443 when you need better strength and thermal performance than 1xxx series alloys while keeping fabrication costs and complexity low. The alloy trades some electrical conductivity and ultimate ductility relative to pure aluminium for improved stiffness, machinability and resistance to thermal distortion.

Compared with commercially pure aluminium (1100), 443 gives higher strength and stiffness but a modest reduction in electrical conductivity and stretch formability. Against common work-hardened alloys such as 3003 or 5052, 443 typically offers comparable or slightly higher strength with similar formability but slightly different corrosion behavior: 5052 will outperform 443 in highly marine environments, whereas 443 may be easier to machine and braze. Versus heat-treatable alloys like 6061 or 6063, 443 will not reach the same peak strengths achievable with T6 treatments but can be preferred where weldability, brazability, dimensional stability during heating and cost are more important than maximum tensile strength.

Use 443 when manufacturing workflows involve extensive forming followed by localized strengthening through cold working or when thermal processes such as brazing are required. Specify tight chemistry and temper control when substituting for other alloys to ensure predictable performance across suppliers.

Closing Summary

Aluminium alloy 443 remains a relevant, pragmatic choice for engineering components that need a balanced combination of formability, moderate strength, good thermal conductivity and economical fabrication. Its silicon-dominant chemistry and work-hardening response make it particularly useful in automotive, marine and thermal-management applications where processability and dimensional stability matter more than absolute peak strength.