ER4643 Aerospace Aluminium Welding Wire
4643 is an aluminium-silicon filler with a small magnesium addition, made for aerospace orders to SAE AMS 4189 and classified ER4643 in AWS A5.10. It is designed for 6061, 6082 and similar alloys that are welded and then solution heat-treated and aged, where it gives higher weld strength than 4043. Metline supplies ER4643 MIG wire and TIG rod worldwide.
- Alloy
- 4643 (Al-4Si-0.2Mg)
- Specs
- AMS 4189 · AWS A5.10 ER4643
- Base metals
- 6061, 6082, 6063, 6005
- Best for
- Post-weld heat-treated joints
The problem 4643 solves
6xxx alloys get their strength from Mg2Si precipitates. A weld made with 4043 contains almost no magnesium, so even if the whole assembly is solution treated and aged afterwards, the weld metal stays soft while the parent metal regains T6 strength.
4643 is essentially 4043 with less silicon and 0.10 – 0.30 % magnesium. The magnesium lets the weld metal form Mg2Si during ageing, so after a full post-weld heat treatment the weld reaches far higher strength than a 4043 weld treated the same way. The lower silicon also improves ductility, while there is still enough silicon to resist hot cracking in crack-sensitive 6xxx joints.
In aerospace and defence work, 4643 is used for welded 6061 assemblies that are re-heat-treated to T6: tanks, frames, housings, electronic enclosures, ducts and ground-equipment structures. It also gives better fillet shear strength than 4043 in many as-welded joints, although 5356 is usually chosen when as-welded shear strength is the only goal.
4643 chemical composition (wt %)
| Element | Limit |
|---|---|
| Silicon (Si) | 3.6 – 4.6 |
| Magnesium (Mg) | 0.10 – 0.30 |
| Iron (Fe) | 0.8 max |
| Copper (Cu) | 0.10 max |
| Manganese (Mn) | 0.05 max |
| Zinc (Zn) | 0.10 max |
| Titanium (Ti) | 0.15 max |
| Beryllium (Be) | 0.0008 max |
| Others, each / total | 0.05 / 0.15 |
| Aluminium (Al) | Remainder |
Physical properties (typical)
- Density
- about 2.69 g/cm³
- Melting range
- about 574 – 635 °C
- Heat-treat response
- Yes, through Mg2Si precipitation
How 4643 compares in heat-treated joints
| Filler | Si % | Mg % | After post-weld solution treatment and ageing | As welded |
|---|---|---|---|---|
| 4043 | 4.5 – 6.0 | 0.05 max | Weld stays relatively soft | Good crack resistance; moderate shear |
| 4643 | 3.6 – 4.6 | 0.10 – 0.30 | Weld hardens; much higher strength than 4043 | Similar to 4043, slightly better ductility |
| 4008 | 6.5 – 7.5 | 0.30 – 0.45 | Matches A356 castings | For castings, not wrought 6xxx |
| 5356 | 0.25 max | 4.5 – 5.5 | Not used for heat-treated 6xxx assemblies | Highest fillet shear of the group |
Exact joint strengths depend on the base alloy, section thickness, joint design, dilution and the heat-treatment cycle, so aerospace procedures qualify the complete sequence. The table shows the direction of the difference, which is what drives filler selection.
Specifications
| Document | Designation | Note |
|---|---|---|
| SAE AMS 4189 | Aluminium alloy welding wire, 4.1Si-0.20Mg (4643) | Aerospace purchasing specification |
| AWS A5.10 | ER4643 / R4643 | Commercial classification |
| ISO 18273 | S Al 4643 (AlSi4Mg) | International classification |
| UNS | A94643 |
Sizes, packing and storage
ER4643 wire supply range
- MIG (GMAW) wire
- Layer-wound spools, typically 0.8, 1.0, 1.2 and 1.6 mm diameter; 100, 200 and 300 mm spools and larger drums
- TIG (GTAW) rod
- Straight cut lengths, typically 1.6, 2.0, 2.4, 3.2, 4.0 and 5.0 mm diameter, about 914 or 1000 mm long
- Condition
- Hard-drawn (H18 / H19-type) for feeding; softer tempers for other wire uses on request
- Surface
- Shaved or cleaned, free of drawing lubricant, oxide and moisture
- Packing
- Sealed bags or cans with desiccant, cartons on pallets; tube packs for TIG rod
- Documents
- EN 10204 3.1 certificate or certificate of conformity with chemical analysis per lot
Diameter tolerance, cast and helix of spooled wire follow AWS A5.10 or the AMS document named on the order.
- Storage: keep wire sealed in its original packing in a dry, heated store; aluminium oxide hydrates and causes weld porosity
- Open spools: return part-used spools to a sealed bag with desiccant, or to a wire cabinet
- Cleaning base metal: degrease, then remove the oxide with a dedicated stainless-steel brush shortly before welding
- Feeding: use U-groove drive rolls, a PTFE or nylon liner and contact tips sized for aluminium
- Traceability: record the lot number from the label on the weld record, so the certificate links to the joint
Welding and heat-treating 6xxx assemblies with 4643
- Plan the sequenceWeld in T4 or O where possible, then solution treat, quench and age the complete assembly to T6.
- PrepareDegrease and brush the joint; remove the oxide just before welding.
- WeldMIG or AC TIG with normal 6xxx parameters; 4643 fluidity is slightly lower than 4043, so allow for bead profile.
- Fixture for heat treatmentSupport the assembly against quench distortion; straighten in the as-quenched state if needed.
- VerifyHardness, tensile coupons and radiography as the procedure requires.
Typical aerospace and defence uses
- Heat-treated weldments: 6061 frames, racks and housings re-aged to T6
- Tanks and pressure parts: 6061 tanks and manifolds heat-treated after welding
- Electronic enclosures: welded and re-heat-treated chassis and boxes
- Ground support equipment: 6xxx structures needing full strength at the weld
- Extrusion assemblies: 6082 and 6005 extrusions joined before final ageing
4643 is not a high-temperature filler and is not used for jet or rocket engine hot sections; those claims in older listings are not correct.
How to order ER4643
- SpecifyAlloy and temper, diameter, spool size or rod length, quantity and the governing specification with its revision (AMS 4189 or AWS A5.10 ER4643).
- ConfirmWe confirm the specification can be met, the tolerance class, test requirements and delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions and surface condition; any extra tests named on the order are carried out or arranged.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 showing chemistry and mechanical results, traceable to the cast or lot number.
- Pack and shipExport packing in sealed, moisture-protected cases or on pallets, shipped by sea or air to your port or door.
References and standards
- SAE AMS 4189 – Aluminum Alloy, Welding Wire, 4.1Si-0.20Mg (4643)
- AWS A5.10/A5.10M – Welding Consumables: Wires and Rods for Aluminum and Aluminum-Alloys, Classification
- ISO 18273 – Welding consumables: wire electrodes, wires and rods for welding of aluminium and aluminium alloys
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
ER4643 aerospace aluminium (aluminum) wire: questions
When should I use 4643 instead of 4043?
When a 6xxx weldment will be solution heat-treated and aged after welding. The magnesium in 4643 lets the weld harden; 4043 welds stay relatively soft.
Is 4643 a good choice for as-welded 6061?
It works, with crack resistance close to 4043. If as-welded fillet shear strength is the priority and anodised colour matters, 5356 is often preferred.
What specification covers 4643 wire?
SAE AMS 4189 for aerospace orders, AWS A5.10 ER4643 for commercial orders, and ISO 18273 S Al 4643.
Can 4643 be used on 5083?
No. Al-Si fillers are not used on high-magnesium 5xxx alloys; use 5356, 5183 or 5556.
Do you supply ER4643 internationally?
Yes. Metline ships ER4643 wire and rod from Mumbai worldwide with lot certificates.
Need ER4643 for heat-treated 6xxx weldments?
Send diameter, form, quantity and specification. We will confirm availability and documents.
