Wrought aluminum alloys in the 1xxx–7xxx series and casting alloys such as LM25 (A356) cover the overwhelming majority of general fabrication work, with selection driven by the trade between formability, weldability, strength, and corrosion resistance rather than by alloy chemistry alone [S1][S2].
The decision framework matters because pure aluminum is soft and reactive, so the alloying partner defines the usable property envelope; downstream operations (forming, machining, welding, anodizing) each gate specific grades, and getting the series wrong at the PO stage costs the whole job [S1].
How the Wrought Series Map to Fabrication Tasks
The 1xxx series (≥99.0% Al) is the softest and most corrosion-resistant wrought family, used where formability and conductivity matter more than strength — chemical tanks, foil, nameplates, and electrical busbars are typical call-outs [S1]. The 3xxx series (Mn-stabilized, e.g. 3003) sits in the middle: ~20% stronger than 1100, weldable, and the workhorse for HVAC ductwork, cookware, and general sheet metal where 5052 is overkill [S1].
For structural sheet and plate, 5052 (Al-Mg, ~2.5% Mg) and 5083 (Al-Mg-Mn, ~4.5% Mg) are the marine-grade defaults: 5052 is weldable and formable for panels and cabinets, while 5083 carries higher strength for hulls and pressure vessels but is not heat-treatable [S1]. The 6xxx series (Al-Mg-Si, e.g. 6061-T6, 6063-T5) dominates extrusions and machined parts because the Mg2Si precipitation response gives 200–310 MPa ultimate tensile strength after T6 aging while keeping extrudability reasonable [S1].
When strength is the only constraint, 7075-T6 (Al-Zn-Mg-Cu) approaches low-alloy steel at ~570 MPa UTS but is poorly welded and more corrosion-sensitive, so it stays in jigs, tooling plates, and aerospace fittings rather than general sheet work [S1]. The 2xxx series (Al-Cu, e.g. 2024) and 7xxx are generally the wrong answer for general fabrication: 2024 is essentially unweldable and the 7xxx family requires special weld procedures.
Castings: LM25/A356 as the Default
LM25 (equivalent to A356) is an aluminum alloy whose stir-cast hybrid composites have been reported as good replacements for automobile components like cylinder heads, cylinder blocks, and wheels, with mechanical properties including hardness, yield stress, ultimate tensile strength, and percentage of elongation [S2].
Published work on LM25 (A356) reinforced with hexagonal boron nitride (h-BN) and boron carbide (B4C) particles — stir-cast then characterized for hardness, yield stress, UTS, and % elongation — confirms the alloy's response to heat treatment and reinforcement loading, and validates it as a base for cylinder heads, blocks, and wheel components where weight and thermal conductivity matter [S2]. Where higher strength is needed in cast form, A357-T6 and A201 raise the ceiling, but most general fabricators should not leave the A356 / LM25 envelope without a specific reason.
Formability, Weldability, and Corrosion Trade-off Matrix
Across the 1xxx, 3xxx, 5xxx, and 6xxx families, four criteria govern most general-fabrication decisions and the matrix looks like this: 1100/3003 win on formability and weldability but bottom out at ~110–150 MPa UTS; 5052/5083 give the best corrosion/weldability balance at 195–290 MPa UTS but are not heat-treatable — strength is from work-hardening only; 6061-T6 jumps to 310 MPa UTS and machines cleanly, but hot-crack susceptibility in welds means GTAW with 5356 or 4043 filler is mandatory; 7075-T6 is essentially not welded in production [S1].
Corrosion resistance follows a simple rule: pure aluminum and Al-Mg alloys (5xxx) are the most resistant and can last decades in atmospheric exposure, while Al-Cu (2xxx) and Al-Zn-Mg-Cu (7xxx) are the least resistant and almost always need a clad (alclad) layer or a coating in service [S1]. For exterior architectural and marine fabrication, 5052/5083 plus a compatible 5xxx filler wire is the conservative default; for indoor structural and machined brackets, 6061-T6 is the default; for chassis and high-stress tooling, 7075 is the upgrade.
Selection Criteria in Order of Weight
For a general fabrication shop, the decision order should run: (1) forming process — deep-drawing sheet points to 3003 or 5052, while extrusion-heavy work points to 6063 for complex profiles or 6061 for higher strength; (2) joining — if production welding is required, eliminate 2xxx and most 7xxx immediately and choose 5xxx for sheet or 6061 with a controlled filler; (3) finishing — anodizing quality is best on 5xxx and 6xxx, while 1xxx gives the brightest decorative finish but at low strength; (4) strength — only escalate to 7075-T6 when the 6xxx ceiling is genuinely binding [S1].
The non-obvious point is that 6063 is often mistaken for 6061 with a slight chemistry nudge. In practice 6063 is the extrusion-grade alloy for architectural shapes, window frames, and irrigation tubing where surface finish and extrudability dominate, while 6061 is the structural extrusion grade for load-bearing parts, truck frames, and machined components where the T6 mechanical properties are required. For an overview of how the construction sector narrows this down further, see the related construction spec map; for thinner-gauge electronics enclosures and heat sinks, the electronics spec map handles a different corner of the same series. The base chemistry and tempering behaviour behind all of this are covered in the aluminum alloy reference, while the aluminum window and door page covers the dominant 6063-T5 extrusion use case in building products.
Limits, Failure Modes, and Common Mis-Selections
The most expensive mis-selection in general fabrication is specifying 6061-T6 for a welded assembly without locking down the filler and procedure: hot-cracking in the HAZ drops joint efficiency well below the 310 MPa parent-metal UTS and the failure often shows up only under fatigue. A second common error is choosing 7075 for a marine or coastal part — its stress-corrosion cracking resistance in the short-transverse direction is poor and even alclad 7075 is a band-aid, not a fix. [S2]
For castings, the boundary condition is section thickness: LM25/A356 tolerates 3–25 mm walls in sand and permanent-mold casting but below ~3 mm the melt becomes hard to feed and porosity rises. Die casters looking for thinner walls should be in the Al-Si hypoeutectic family (A383, A384) or pressure die-casting alloys rather than A356. The die casting machine encyclopedia covers the process-side constraints when thinner castings are unavoidable.
Sourcing and Standards to Lock at the PO
Every general-fabrication PO should reference the temper designation (O, H32, H34, T4, T5, T6) alongside the alloy, because the same 6061-O and 6061-T6 differ by a factor of three in yield strength and the mill cert — not the alloy code — is the legal proof of compliance. For BS-aligned castings, BS 1490:1988 specifies LM25 chemistry and mechanical-property ranges and remains the cited standard in published LM25 experimental work [S2].
For wrought products, ASTM B209 (sheet/plate), B221 (extruded bar/rod/wire), and B308 (structural 6061-T6) are the call-outs most specifiers will land on, and the aluminum veneer panel entry is a useful worked example of how 3003 and 5052 are paired with coating systems in architectural skin applications. For the upstream melt side, gas aluminum melting furnace pages detail the holding-furnace side of casting-alloy production, and the aluminum ladder entry is a clean worked example of 6061-T6 / 6063-T5 mixing in a fabricated consumer product where both strength and extrudability are required.
The next signal worth watching is the 2026 revision track on ASTM B209 and the harmonization of BS 1490 LM25 with the older A356.0 / A356.2 chemistry limits — published mechanical-property tables on stir-cast LM25/A356 hybrid composites in 2022 (h-BN and B4C reinforcements) already show a credible path to higher hardness and UTS without leaving the A356 envelope [S2], so any shop buying castings should plan to retest its incoming spec against the latest ASTM/BS tables before Q4 2026 rather than rely on data older than 2020.