aluminum-alloys

name	aluminum-alloys
description	Aluminum alloy designation, tempers, properties table (2xxx, 5xxx, 6xxx, 7xxx), weldability, formability, corrosion resistance, selection guide, casting alloys.
metadata	{"priority":7,"promptSignals":{"phrases":["aluminum alloy","aluminium alloy","6061","7075","2024","Al alloy","aluminum temper"],"minScore":3}}

Aluminum Alloys — Complete Skill

Designation System (AA/ANSI)

4-digit wrought: XXXX 1st digit = major alloying element: 1=pure Al, 2=Cu, 3=Mn, 4=Si, 5=Mg, 6=Mg+Si, 7=Zn, 8=other 2nd digit: modification (0=original, 1-9=modification) 3rd+4th: minimum Al % or arbitrary designation

Temper designations (after dash): -F: as fabricated; -O: annealed; -H: strain hardened; -T: thermally treated -T4: solution heat treated + naturally aged -T6: solution + artificially aged (peak strength) -T73: solution + over-aged (improved SCC resistance, -10% strength vs T6) -T76: solution + over-aged (intermediate) -T851: T8 + stress relieved (stretched)

Properties by Series

2xxx Series (Al-Cu, high strength)

2024-T3: S_y = 345 MPa, S_u = 483 MPa, El = 18%, E = 73 GPa — aerospace structure 2024-T4: S_y = 324 MPa, S_u = 469 MPa, El = 20% 2014-T6: S_y = 414 MPa, S_u = 483 MPa — structural applications, forgings Weldability: poor (hot cracking); use adhesive or rivets Corrosion: susceptible; requires cladding (Alclad) or anodizing

5xxx Series (Al-Mg, moderate strength, non-heat-treatable)

5052-H32: S_y = 193 MPa, S_u = 228 MPa — sheet, marine, fuel tanks 5083-H116: S_y = 228 MPa, S_u = 317 MPa — marine, cryogenic, weldable structures 5086-H112: S_y = 152 MPa, S_u = 262 MPa Excellent weldability (match with 5356 filler); good corrosion resistance; not age-hardenable

6xxx Series (Al-Mg-Si, medium strength, excellent all-rounder)

6061-T6: S_y = 276 MPa, S_u = 310 MPa, El = 12% — structural, extrusions, machined parts 6063-T5: S_y = 145 MPa, S_u = 186 MPa — architectural extrusions 6082-T6: S_y = 260 MPa, S_u = 310 MPa (European equivalent to 6061) Good weldability (4043 or 5356 filler), good formability, excellent extrude-ability Corrosion: good; anodizes well; slight HAZ softening after welding

7xxx Series (Al-Zn, highest strength)

7075-T6: S_y = 503 MPa, S_u = 572 MPa, El = 11% — highest strength wrought Al 7075-T73: S_y = 435 MPa, S_u = 503 MPa — SCC resistant version 7050-T7451: S_y = 455 MPa, S_u = 510 MPa — aerospace thick plates 7150-T7751: S_y = 490 MPa, S_u = 525 MPa — upper wing stringers Weldability: poor; typically riveted or bonded Corrosion: susceptible (use -T73/-T76 for SCC); use Alclad or anodize

Casting Alloys (3-digit + decimal)

A356.0-T6: S_y = 207 MPa, S_u = 262 MPa, El = 6% — most common casting alloy (wheels, engine) 319.0-T6: S_y = 165 MPa, S_u = 250 MPa — engine blocks, cylinder heads 380.0 (die cast): S_y = 165 MPa, S_u = 317 MPa — general die castings

Corrosion Behavior

Naturally forms protective Al₂O₃ film: self-passivating in air Susceptible environments: saltwater (pitting), alkaline solutions Galvanic: Al is anodic vs. most metals; acceptable vs. stainless (same coating condition) Anodizing: thickens oxide (5-25 μm type II; 25-100 μm hardcoat type III)

Selection Guide

Application	Alloy	Reason
Aerospace wing skins	2024-T3	Fatigue; damage tolerance
Aerospace wing spars	7075-T6 or 7150	Highest strength
Extrusions (structural)	6061-T6	Extrudable, weldable, structural
Marine (welded)	5083-H116	Weldable, corrosion resistant
Machined precision parts	6061-T6 or 7075-T6	Machinability + strength
Automotive castings	A356-T6	Castability + strength
Architectural	6063-T5	Surface quality, anodizing

Weldability Guide

5xxx → 5xxx: use 5356 filler (ER5356) 6061 → 6061: use 4043 filler (lower crack susceptibility) or 5356 (higher strength joint) 2xxx and 7xxx: generally non-weldable by fusion; use FSW or mechanical fastening Joint efficiency: 6061-T6 weld → joint = ~55% of parent (HAZ softens to T4 equivalent)

Output

Provide: alloy and temper recommendation, S_y and S_u [MPa], density [kg/m³], weld filler if applicable, corrosion protection recommendation, applicable heat treatment, fatigue endurance limit [MPa].