4043 Aluminum

Representative aluminum raw/semi-finished material photo; exact grade not verified

4043 Aluminum (AA 4043) is a registered wrought aluminum–silicon alloy best known as a welding wire and rod filler metal. Its 4.5–6.0% silicon content lowers the melting range relative to many base aluminum alloys, promotes fluid weld-pool behavior, and helps reduce solidification-cracking tendency. It is widely selected for welding 6xxx-series aluminum and cast aluminum components where color match after anodizing is not critical. Published mechanical data must be interpreted by product form: wire, deposited weld metal, and wrought stock can have substantially different properties.

Chemical Composition (wt.%)
Chemical Composition wt.%
Element	Min	Max
Silicon	4.5	6.0
Iron	—	0.8
Copper	—	0.30
Manganese	—	0.05
Magnesium	—	0.05
Zinc	—	0.10
Titanium	—	0.20
Others, each	—	0.05
Others, total	—	0.15
Aluminum	Remainder

Composition notes

Others, each: Unspecified elements.
Others, total: Total of unspecified elements.

Registered wrought-alloy composition limits, in mass percent. Aluminum is the remainder. The listed “Others” limits apply as 0.05% maximum for each unspecified element and 0.15% maximum total.

Values below are published for 4043 alloy or 4043 welding product as identified by the respective source. Mechanical values are not universal design allowables for 4043 filler metal or for a particular welded joint.

Use the button to switch between Metric and US Customary units.

Table of 4043 Aluminum Properties

Table of 4043 Aluminum Properties
Physical Properties	Metric
Density	2.69 g/cm³2.69 g/cm³
Mechanical Properties	Metric
Tensile Strength	145 MPa
Yield Strength (12.7 mm diameter)	70 MPa
Elongation at Break (12.7 mm diameter)	22 %
Shear Strength	90 MPa
Brinell Hardness	39 HB
Poisson’s Ratio	0.34
Thermal Properties	Metric
Mean Coefficient of Thermal Expansion (20–100°C) (20–100°C)	22.1 µm/m·°C
Thermal Conductivity	163 W/m·K
Melting Range	574–632 °C
Electrical Properties	Metric
Electrical Conductivity (-O)	42 % IACS

Test conditions & data notes

Density: Calculated nominal density for active wrought alloy 4043.
Tensile Strength: Published 4043 alloy value; product form and temper not stated in the cited table.
Yield Strength (12.7 mm diameter): At 12.7 mm (0.500 in) diameter; temper not stated.
Elongation at Break (12.7 mm diameter): At 12.7 mm (0.500 in) diameter; temper not stated.
Shear Strength: Temper and product form not stated.
Brinell Hardness: Published with 500 kg load and 10.0 mm thickness; temper not stated.
Poisson’s Ratio: Temper and product form not stated.
Mean Coefficient of Thermal Expansion (20–100°C) (20–100°C): Average over (68–212°F).
Thermal Conductivity: Temperature and product condition not stated.
Electrical Conductivity (-O): 4043 welding-product listing; -O condition.
Melting Range: 4043 welding-product listing.

Material Conditions & Tempers

4043 is commonly supplied as bare welding wire or rod, including annealed (-O) product. Its designation does not include a temper. Select wire diameter, spool/rod form, surface condition, shielding gas, and the required deposited-weld-metal performance from the applicable filler-metal specification and supplier documentation. Do not apply mechanical-property values from a generic wrought product directly to a welded assembly.

Condition	Description	Notes
-O	Annealed condition commonly cited for 4043 welding product electrical-conductivity data.	The supplied source reports conductivity for -O, but does not provide a complete strength set for this condition.
As-supplied welding wire or rod	Commercial filler-metal product condition used for GTAW and GMAW applications.	Weld-joint and deposited-metal properties depend on base metal, dilution, joint design, and welding procedure.

Advantages & Limitations

Advantages	Limitations
The 4.5–6.0% silicon range gives a comparatively fluid weld pool and a lower melting range than many aluminum base alloys. 4043 is a long-established general-purpose filler for many 6xxx-series and aluminum casting welding jobs. Low magnesium content makes it distinct from 5xxx-series fillers and can be advantageous where a silicon-bearing filler is specified. The alloy has a calculated nominal density of 2.69 g/cm³, retaining aluminum’s favorable mass efficiency. It is also used where smooth bead appearance and reduced hot-cracking sensitivity are more important than maximum weld-metal strength.	4043 weld metal may anodize gray or dark relative to the surrounding base metal; it is not preferred when a close decorative anodized color match is required. It is not a substitute for higher-strength Mg-containing filler metals when the application requires their specific joint-strength or service characteristics. Welded-joint performance is governed by base alloy, dilution, heat input, filler size, shielding gas, and post-weld condition; generic 4043 tensile values are not joint design allowables. For elevated-temperature, fatigue-critical, corrosive, or code-controlled service, qualify the filler and welding procedure for the actual joint and environment.

Advantages

Limitations

The 4.5–6.0% silicon range gives a comparatively fluid weld pool and a lower melting range than many aluminum base alloys.
4043 is a long-established general-purpose filler for many 6xxx-series and aluminum casting welding jobs.
Low magnesium content makes it distinct from 5xxx-series fillers and can be advantageous where a silicon-bearing filler is specified.
The alloy has a calculated nominal density of 2.69 g/cm³, retaining aluminum’s favorable mass efficiency.
It is also used where smooth bead appearance and reduced hot-cracking sensitivity are more important than maximum weld-metal strength.

4043 weld metal may anodize gray or dark relative to the surrounding base metal; it is not preferred when a close decorative anodized color match is required.
It is not a substitute for higher-strength Mg-containing filler metals when the application requires their specific joint-strength or service characteristics.
Welded-joint performance is governed by base alloy, dilution, heat input, filler size, shielding gas, and post-weld condition; generic 4043 tensile values are not joint design allowables.
For elevated-temperature, fatigue-critical, corrosive, or code-controlled service, qualify the filler and welding procedure for the actual joint and environment.

Processing & Fabrication

Process	Description
GTAW and GMAW welding	4043 is commonly supplied as rod or continuous wire for gas-tungsten-arc and gas-metal-arc welding. Clean oxide, moisture, oil, and shop contamination from the joint because aluminum oxide and hydrogen contamination can impair weld quality.
Filler-metal selection	Use 4043 particularly for compatible 6xxx-series and cast-aluminum welding applications where its silicon-rich chemistry, fluidity, and crack-resistance characteristics suit the joint. Confirm compatibility with the base-material specification and required post-weld finish.
Weld procedure control	Control heat input, joint fit-up, shielding coverage, and interpass practice to obtain consistent penetration and bead profile. Actual deposited composition changes with base-metal dilution, especially when joining dissimilar alloys.
Anodizing and finishing	Plan finish trials when appearance matters. Silicon-containing 4043 deposits can contrast visibly with adjacent base metal after anodizing; mechanical finishing alone may not eliminate this color difference.

Applications

4043 is principally a consumable alloy rather than a general structural sheet grade. Its use is driven by weldability, bead fluidity, and compatibility with common aluminum fabrication alloys and castings.

6xxx-series aluminum fabrication: Provides a silicon-rich filler option for welded frames, extrusions, and fabricated components where crack-resistant welding behavior is required.
Aluminum castings repair and joining: Its fluid weld pool is useful for many cast-aluminum repair, build-up, and joining operations, subject to evaluation of the casting chemistry and contamination.
Automotive and transportation components: Used for production or repair welding of compatible aluminum parts where a conventional 4043 wire specification is called out.
General aluminum maintenance welding: Available as wire and rod for versatile GTAW/GMAW repair work when base-metal and service requirements permit 4043.

Standards & Designations

Designation	Value	Description
Aluminum Association registered wrought designation	4043	Active registered wrought aluminum-alloy designation; composition limits are listed in the Aluminum Association Teal Sheets.
ISO former designation / Declaration of Accord cross reference	AlSi5	The Teal Sheets cross-reference table identifies 4043 with former ISO designation AlSi5.
ANSI/AWS	A5.10 ER4043 / R4043	Listed by a 4043 welding-product supplier as a specification met or exceeded; confirm the current specification revision and product qualification.
SAE AMS	AMS 4190	Listed by a 4043 welding-product supplier; verify the applicable revision and product-form scope before procurement.

Frequently Asked Questions

What is the difference between 4043 and 4043A aluminum?

They are separate registered wrought-alloy designations. Both have 4.5–6.0% silicon, but their registered impurity and minor-element limits differ. For example, the supplied Aluminum Association record lists 4043 with maxima of 0.8% Fe, 0.05% Mn, and 0.05% Mg, whereas 4043A has different listed limits. Do not substitute them solely on the basis of their similar names.

Why is 4043 frequently used as an aluminum welding filler?

Its silicon content lowers the melting range and improves weld-pool fluidity. These characteristics make 4043 a common filler choice for many compatible 6xxx-series aluminum and cast-aluminum welding applications, particularly when reduced solidification-cracking tendency is desired.

Can 4043 welds be anodized to match the base aluminum?

They can be anodized, but a close color match should not be assumed. Silicon-bearing 4043 weld deposits commonly appear gray or dark compared with adjacent base metal after anodizing. Make representative welding and finishing trials when cosmetic anodized appearance is a requirement.

References & Data Notes

(n.d.). The Aluminum Association — International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys (Teal Sheets, December 2025). https://www.aluminum.org/sites/default/files/2026-01/Teal%20Sheets%20December%202025.pdf
(n.d.). AZoM — Aluminum 4043 Alloy (UNS A94043). https://www.azom.com/article.aspx?ArticleID=8685
(n.d.). ASM Digital Library — ALUMINUM 4043 Welding Wire, Alloy Digest. https://dl.asminternational.org/alloy-digest/article/18/2/Al-184/1622/ALUMINUM-4043Welding-Wire
(n.d.). Aufhauser — Aluminum 4043. https://www.brazing.com/products/Welding_alloys/alloy4043.aspx

Composition limits and calculated nominal density are from the Aluminum Association registered wrought-alloy record. Other numerical properties are source-reported 4043 values and must be used only with their stated or available product-condition qualifications. In particular, welding wire, deposited weld metal, and finished welded joints are different material states.