Aluminum 4047: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 4047 is a member of the 4xxx series of aluminum alloys, a family characterized by silicon as the primary alloying element. The 4xxx series is conventionally used for filler metals, welding, brazing and where silicon improves fluidity and reduces melting range. 4047 contains a relatively high silicon content (typically in the double-digit percent range), with small additions or residuals of iron, copper, manganese, titanium and other trace elements. This composition places 4047 in the class of Al-Si alloys that are not conventionally strengthened by precipitation heat treatment.

The principal strengthening mechanism for 4047 is not age hardening; instead, properties are controlled by microstructure (Si particle distribution), cast/extrusion structure and cold working when applicable. In annealed condition the alloy is relatively soft and highly formable; cold working (H-tempers) increases strength at the expense of ductility. Key traits are excellent fluidity and reduced hot-cracking tendency in welding or brazing, good corrosion resistance typical of Al-Si alloys, and reasonable machinability compared with higher-strength Al alloys.

Typical industries using 4047 include automotive (as filler for joining and in cast components), HVAC and refrigeration (heat exchangers and brazing), building and fenestration (welded or brazed frames), and electronics (solderable connections and some packaging). It is often chosen over other aluminum alloys when a low melting range, high fluidity filler, or a silicon-rich matrix is required to avoid weld hot-cracking or to improve filler flow in brazing operations. Designers select 4047 when welding compatibility, brazing performance, or filler-specific properties are the dominant requirement rather than maximum structural strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition; best for forming and brazing filler stock
H14	Medium	Low–Moderate	Fair	Excellent	Strain-hardened to a half-hard condition for increased stiffness
H18	Medium–High	Low	Limited	Very Good	Strain-hardened to full hard for maximum cold-worked strength
H32	Medium	Moderate	Good	Excellent	Strain-hardened and stabilized; balances strength and ductility
F	Variable	Variable	Variable	Excellent	As fabricated or cast; properties depend on processing
ER4047 (filler)	Designed for flow, not high strength	N/A	N/A	Excellent	Sold as filler wire/rod for welding and brazing applications

Temper dramatically modifies the mechanical behavior of 4047 because the alloy is not age-hardenable; work hardening and microstructural control are the primary levers. Annealed (O) material exhibits the highest ductility and formability and is preferred for forming operations and as a brazing filler; H-tempers raise yield and tensile strength through cold work while reducing elongation.

In practice, selection of temper is a tradeoff between formability and strength for each fabrication stage. For welded assemblies that require post-weld forming, O temper is often chosen, while structural non-heat-treated parts that need higher stiffness may be specified in H14 or H18.

Chemical Composition

Element	% Range	Notes
Si	11.0–13.5	Primary alloying element; lowers melting range and improves fluidity
Fe	≤ 0.95	Common impurity; forms intermetallics that can affect toughness
Mn	≤ 0.20	Minor addition; can refine grain and stabilize microstructure
Mg	≤ 0.05	Essentially absent; little contribution to strength via precipitation
Cu	≤ 0.30	Small amounts can marginally increase strength but lower corrosion resistance
Zn	≤ 0.10	Minor impurity; not a deliberate strengthening addition
Cr	≤ 0.05	Trace element; can inhibit grain growth in cast conditions
Ti	≤ 0.10	Grain refiner in cast/extruded stock
Others (each)	≤ 0.05	Residual elements; total others ≤ 0.15

The high silicon fraction defines the alloy’s performance envelope: silicon forms a dispersed second phase (eutectic and primary Si) that controls casting microstructure, fluidity and solidification characteristics. Iron and other residuals produce intermetallic particles which can act as crack initiation sites under cyclical loading or machining if not well controlled. Because magnesium and copper are low, 4047 gains minimal benefit from precipitation hardening, so designers must rely on work hardening and microstructural control to manipulate mechanical properties.

Mechanical Properties

Tensile behavior in 4047 is governed by silicon morphology and the degree of cold work rather than by classical precipitation strengthening. In annealed state the alloy displays moderate ultimate tensile strength and relatively high elongation, making it forgiving for forming operations and for use as filler metal in welded joints. Cold working significantly raises yield and tensile strength while reducing ductility; the highest practical strengths are achieved in fully cold-worked tempers where Si particle interactions and strain hardening dominate.

Yield strength in annealed 4047 is low compared with heat-treatable alloys; however, the alloy's fracture toughness in ductile conditions remains adequate for many joining and non-structural applications. Hardness correlates closely with temper: annealed material will be soft (low Brinell/HV), while H-tempers can exhibit notable hardness increases depending on degree of cold work. Fatigue performance is moderate; fatigue life is sensitive to surface condition, Si particle distribution and any casting defects or intermetallic clusters.

Thickness and section geometry influence measured strengths: thin sheet in O temper will show higher apparent ductility and lower absolute strength, while thicker cast or extruded sections may contain primary silicon particles and porosity that reduce ductility and fatigue life. Welding and brazing processes typically use ER4047 filler to produce joints with good toughness and minimized hot-cracking, though the local microstructure in the HAZ must be considered for cyclic or high-stress applications.

Property	O/Annealed	Key Temper (e.g., H14/H18)	Notes
Tensile Strength	~60–110 MPa	~120–170 MPa	Values depend on cold work and section; broad engineering ranges shown
Yield Strength	~25–50 MPa	~90–140 MPa	Yield rises markedly with strain-hardening tempers
Elongation	~10–25%	~2–8%	Ductility drops as temper increases; O temper is best for forming
Hardness	~20–35 HB	~35–70 HB	Hardness scales with cold work and Si dispersion

Physical Properties

Property	Value	Notes
Density	2.67 g/cm³	Typical for Al-Si alloys; slightly lower than many ferrous materials
Melting Range	Solidus ~555–565 °C; Liquidus ~615–625 °C	Silicon broadens the solidification range compared with pure Al
Thermal Conductivity	~120–160 W/m·K	Reduced from pure Al due to silicon and intermetallics; depends on temper
Electrical Conductivity	~30% IACS (≈17–18 MS/m)	Alloying reduces conductivity versus pure Al
Specific Heat	~900 J/kg·K	Typical for aluminum alloys at ambient temperature
Thermal Expansion	~21–24 µm/m·K	Coefficient similar to other Al alloys; varies slightly with Si content

4047’s density and specific heat are close to other aluminum alloys, which makes it attractive where weight and thermal capacity are design drivers. Thermal conductivity is reduced from pure aluminum but remains high compared to most structural metals, making 4047 useful in applications requiring heat transfer coupled with low melting range fillers.

The melted/solidification behavior is a defining characteristic: the lowered melting range and improved fluidity due to high silicon content are exploited in brazing and repair processes. Electrical conductivity is lower than for commercially pure aluminum but still acceptable when moderate conductivity is required alongside good joining performance.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Lower strength in O; H-tempers available	O, H14, H32	Widely used for brazing stock and light fabrication
Plate	>6 mm	Strength depends on work and section size	O, F	Thicker sections can develop primary Si and porosity in castings
Extrusion	Profiles up to several meters	Strength influenced by extrusion/aging history	O, H32, H14	Used where complex profiles and filler compatibility are needed
Tube	OD 6 mm–200 mm	Similar to sheet; wall thickness influences properties	O, H18	Tubing often supplied annealed for forming and bending
Bar/Rod	Diameters 1–25 mm	Often sold as filler wire or rod	F, O, ER4047	Common as welding/brazing wire (ER4047) with controlled Si for flow

Form affects microstructure and therefore mechanical response: cast components can contain primary silicon phases and intermetallics not present in wrought sheet and extrusion. Sheet and extruded forms are more uniform and can be strain-hardened to H-tempers for additional strength. Filler wire/rod forms (ER4047) are specially processed to ensure consistent chemistry and melting behavior for joining operations.

Selection of a product form depends on the balance of formability requirements, section thickness (which affects cooling and Si segregation), and whether the primary use is structural or as filler material in joining. Fabrication processes such as bending, punching and welding each have preferred starting tempers and thicknesses to minimize defects.

Equivalent Grades

Standard	Grade	Region	Notes
AA	4047	USA	Aluminum Association designation commonly used for filler and wrought stock
EN AW	4047	Europe	Often referenced as EN AW-4047 for wrought equivalents or filler designations
JIS	A4047 / A4047S	Japan	Filler/wire designations exist under JIS for brazing and welding consumables
GB/T	4047	China	Chinese standards provide similar alloy classification and typical chemistries

Differences between standards are usually subtle and relate to specified impurity limits, permitted lot-to-lot variations, and form-specific processing requirements. For welding and brazing consumables, regional standards may prescribe slightly different Si ranges or residual control to optimize flow and minimize porosity. Always verify the exact specification sheet (chemical limits, mechanical requirements and certification) when substituting between regional grades.

Corrosion Resistance

In atmospheric environments 4047 generally displays good corrosion resistance owing to the protective aluminum oxide layer and the presence of silicon which does not significantly promote pitting. The alloy performs well in moderate outdoor environments, and typical anodic behavior is similar to many aluminum alloys that are not heavily alloyed with Mg or Cu. Localized corrosion can occur at sites with intermetallic clusters or casting porosity but is less pronounced than in some high-copper alloys.

Marine behavior is acceptable for many applications but is not as robust as marine-grade 5xxx alloys (magnesium-containing), which are specifically optimized for saltwater service. For immersed or splash-zone applications, designers should consider sacrificial protection, coatings or use a different alloy if long-term exposure to seawater is expected. Galvanic interactions follow typical aluminum conventions: when coupled to more noble metals (stainless steel, copper), aluminum will corrode preferentially unless electrically isolated or protected.

Stress corrosion cracking susceptibility is low for silicon-rich, non-heat-treatable alloys like 4047 compared with high-strength Al-Zn-Mg alloys. However, residual stresses from welding, cold work and surface defects can affect long-term performance under tensile and corrosive conditions. Compared with common alloy families, 4047 offers better weldability and brazing performance but slightly lower pitting resistance in chloride environments than specially tailored marine alloys.

Fabrication Properties

Weldability

4047 is widely used as a filler alloy (ER4047) because its high silicon content lowers melting temperature and improves fluidity, which reduces the tendency for hot cracking in many aluminum base metals. It is especially suited as a filler for 6xxx series base metals where silicon-rich filler mitigates weld-solidification cracking. Common welding processes include TIG and MIG/GMAW using ER4047 wire, and brazing/soldering applications where a controlled melting range is required. Hot-cracking risk is lower than many other fillers, but excessive Si segregation or poor joint fit-up can still cause brittle phases or porosity; proper joint preparation and travel speeds are essential.

Machinability

Machinability of 4047 is moderate: the presence of hard silicon particles can increase tool wear compared with pure aluminum but improves chip breaking relative to some soft alloys. Carbide tooling and sharp geometry are recommended for high-feed or high-speed operations. Cutting speeds can be higher than for ferrous metals but should be modest relative to high-speed machining of wrought aluminum; coolant use and chip evacuation are important to avoid built-up edge and surface work-hardening. Cast or extruded forms with coarse primary silicon will be more abrasive and demand more frequent tool change than fine-grained wrought sheet.

Formability

Formability is excellent in annealed (O) condition, with good bendability and drawability for sheet and thin-walled sections. Minimum bend radii depend on temper and thickness; in O temper a rule of thumb is 2–3× material thickness for typical V-bending, whereas H-tempers will require larger radii and may crack at tight bends. Cold forming work hardens the material, so intermediate anneals are used for multiple forming operations. For applications requiring severe forming, choose O temper and control tooling radii and lubrication to avoid surface cracking around silicon particles.

Heat Treatment Behavior

4047 is classified as a non-heat-treatable alloy in the sense that conventional solution-and-age processes do not produce significant precipitation strengthening. Attempting a T6-type heat-treatment offers negligible benefit because there is insufficient alloying content (Mg, Cu) to form strengthening precipitates. Solution treatment and artificial aging do not appreciably change mechanical properties beyond possible microstructural homogenization and relief of casting segregation.

Annealing is the primary thermal processing route: full anneal is typically done at elevated temperatures (e.g., 350–420 °C depending on section and specification) followed by controlled cooling to restore ductility and soften strain-hardened tempers. Stabilization treatments (e.g., H32) may be used to minimize natural aging effects or to set a predictable balance between strength and ductility. For filler and welding applications, controlled heat input during joining is more important than post-weld heat treatment because the alloy’s properties are primarily determined by microstructure and work hardening.

High-Temperature Performance

At elevated temperatures 4047 experiences progressive strength reduction as with other aluminum alloys; significant losses in yield and tensile strength occur above roughly 150–200 °C. Creep resistance is limited compared with specialized high-temperature alloys, so 4047 is not recommended for sustained high-stress service at elevated temperatures. Oxidation is limited by formation of an aluminum oxide film, but prolonged exposure to high temperatures in oxidizing atmospheres can degrade surface appearance and joint integrity.

In welded assemblies, HAZ behavior is generally benign because the alloy is not precipitation-hardening, but softening and microstructural coarsening can occur with prolonged thermal exposure. For brazing and lower-temperature joining processes 4047 performs well, but designers should avoid operating near the alloy’s melting range or in environments where repeated thermal cycling could cause grain coarsening or embrittlement associated with silicon-rich phases.

Applications

Industry	Example Component	Why 4047 Is Used
Automotive	Brazed heat exchangers, filler for welding body components	Excellent filler fluidity and reduced hot-cracking for joining operations
HVAC / Refrigeration	Evaporators and condensers (brazed)	Low melting range and good flow for brazed joint manufacture
Building / Fenestration	Welded window and door frames	Good weldability and corrosion resistance for fabricated assemblies
Electronics	Solderable joints, some heat spreader components	Good thermal conductivity and filler properties for joining
General Manufacturing	Filler wire/rod for aluminum repair and fabrication	ER4047 widely available as filler with predictable melt behavior

4047 is particularly valuable where joining quality and filler behavior are the priority. The alloy’s combination of high silicon content, good flow, and low hot-cracking sensitivity make it a go-to choice for manufacturers of heat exchangers, brazed assemblies and for repair/welding shops that require reliable filler performance. Its use as a structural alloy is limited compared with heat-treatable alloys, so its role is often complementary in multi-material assemblies.

Selection Insights

Choose 4047 when joining or brazing performance and flowability are primary requirements rather than peak structural strength. It is the default filler choice when welding 6xxx series base metals to reduce hot-cracking or when a silicon-rich filler improves joint quality.

Compared with commercially pure aluminum (e.g., 1100), 4047 trades some electrical conductivity and basic formability for improved fluidity during melting and superior filler behavior for brazing and welding operations. Compared with work-hardened alloys such as 3003 or 5052, 4047 offers similar or slightly lower structural strength but better weld/braze compatibility and lower hot-crack susceptibility. Against common heat-treatable alloys like 6061/6063, 4047 will not reach their peak strengths but is preferred when a low melting range filler or a silicon-rich alloy is required to ensure joint integrity and flow.

Closing Summary

Aluminum 4047 remains relevant as a specialty Al-Si alloy that excels as a filler and brazing material and in applications where silicon-enhanced fluidity and low hot-cracking tendency are critical. Its non-heat-treatable nature directs its use toward joining, repair, and specific wrought or cast forms rather than high-strength structural roles, making it a practical, widely available solution for many manufacturing joining challenges.