6061 vs 7075 Aluminum for Aerospace Parts

Updated October 13, 2026

6061 vs 7075 side by side, with the source for every number

7075 has roughly 1.8 times the typical yield strength of 6061 for about 4 percent more weight, but it gives up weldability and, in the T6 temper, stress corrosion resistance. The table separates typical values from specification minimums. Design to MMPDS allowables or to the minimums in the procurement spec for your exact product form and thickness, never to the typical columns.

Sources by column: 6061 typical values are from the Protolabs 6061-T651/T6 data sheet (2026); the 6061 minimums are the published spec minimums summarized in the 6061 alloy reference. 7075-T651 typical values, the machinability and weldability letter ratings are from Continental Steel's 7075-T651 plate page, which cites AMS-QQ-A-250/12 and ASTM B209. 7075-T7351 typical values and the plate minimums are from Referans Metal's AMS 4078 product page. Stress corrosion ratings are from NASA MSFC-STD-3029 Revision A, Tables I and III. Dividing typical yield by density gives the 1.8 times figure; treat it as a comparison, not an allowable.

Choose 6061 when, choose 7075 when

Start from the load case and the environment, not the strength number. Most brackets, housings and ground support structure do not need 7075, and most highly loaded machined fittings cannot use 6061 without growing heavy.

Choose 6061-T6 or T651 when

• The part will be fusion welded, or may be repaired by welding later.
• It sits in salt air with sustained stress and you want a Table I material with no approval step on a NASA program.
• Stiffness, not strength, sizes the part. The modulus is within about 4 percent of 7075, so a stiffness-driven part gains little from the stronger alloy.
• It is GSE, a fixture, an enclosure or a frame where cost, availability and welding matter more than weight.
• You need extrusions or tube in many shapes; 6061 is a mainstream extrusion alloy covered by ASTM B221.

Choose 7075 when

• Strength per pound sizes the part: lugs, fittings, brackets in primary load paths, high-load flight hardware.
• Shear or bearing strength governs, since typical shear strength is about 60 percent higher.
• Fatigue under cyclic load matters, with the endurance numbers above as a first indication only.
• The part is machined, fastened, and never welded.
• You can accept T73 or T7351 strength for stress corrosion resistance, or you can document a low sustained stress if you keep T6.

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Stress corrosion: the temper decides, not the alloy name

On NASA hardware 6061 needs no stress corrosion approval in any temper, 7075-T73 needs none, and 7075-T6 needs approval and a documented low sustained stress. MSFC-STD-3029 sorts alloys by test result in 3.5 percent sodium chloride alternate immersion or 5 percent salt spray:

• Table I, high resistance: no failures within 30 days on specimens stressed to 75 percent of yield. Used preferentially; no NASA approval required.
• Table II, moderate: no failures within 30 days at 50 percent of yield. Requires approval, and the standard bars Table II materials from high installation stress uses such as springs and fasteners.
• Table III, low: failures at 50 percent of yield. Usable only where sustained tensile stress in the critical grain direction is shown to be well below the measured threshold, with protective measures.

7075-T6 is in Table III, 7075-T76 in Table II, and 7075-T73 in Table I. 6061 is listed under the 6000 series in Table I for all tempers. Two details catch people. The sheet exemption in the standard, which treats material under 0.25 inch thick as resistant, applies only to Table II aluminum conditions, so it does not cover 7075-T6. And the standard states that protective coatings do not change the stress corrosion rating, so anodize or primer on a T6 fitting does not move it to an acceptable category.

The cost of the move from T6 to T73 class is visible in the typical values: about 73 ksi yield drops to about 63 ksi. For a part with a press-fit bushing, a tapered pipe thread or clamp-up across the plate thickness, that 10 ksi is usually the right trade. For the grain direction rules and the residual stress figures, see the aluminum alloys page.

Welding and joining

6061 is the weldable choice; treat 7075 as a machine-and-fasten alloy. Published data shows 6061 welds well by TIG or MIG with 4043 or 5356 filler, but the zone next to the weld drops to roughly T4 properties, a loss of around 40 percent, and the Aluminum Design Manual recommends a 24 ksi design strength adjacent to the weld without post-weld heat treatment. A welded 6061 assembly can be solution treated and aged again to recover most of its strength, at the price of distortion and a heat treat fixture.

7075 is rated D, the lowest grade, for gas and arc welding in the letter scale Continental Steel publishes, while resistance spot and seam welding rate B. In practice 7075 structure is joined with fasteners, and a design that seems to need a welded 7075 frame usually becomes a 6061 or 2219 weldment or a machined 7075 one-piece part. Weld procedure and inspection detail is on the sheet metal and aerospace welding page.

Anodize, chem film and finish response

Both alloys anodize well under MIL-PRF-8625, and both fall under the same hard coat wear limit. MIL-A-8625F sets the Type III wear index at 3.5 mg per 1,000 Taber cycles maximum for alloys with 2 percent copper or more and 1.5 mg for other alloys. The SAE titles for AMS 4027 and AMS 4045 give nominal copper of 0.28 percent for 6061 and 1.6 percent for 7075, so both are judged against the tighter 1.5 mg limit, unlike 2024.

Practical differences to flow down:

• Appearance. 6061 gives the most predictable color and clear coat across lots. If a 7075 part has a cosmetic requirement, ask for a coupon in the actual alloy and temper.
• Corrosion protection matters more on 7075. Continental rates 7075 general corrosion resistance C, which by its footnote means faying surfaces generally need protection. Seal the anodize, prime faying surfaces and wet-install fasteners where the drawing allows.
• Coatings and SCC. Repeat the point above on the drawing review: a finish does not fix a Table III temper.

Process controls, sealing, and dimensional growth are covered on the anodizing and chemical conversion coating pages, so they are not repeated here.

Machinability and distortion

Both alloys machine fast; the usual problems are distortion and handling, not tool wear. Continental rates 7075-T651 machinability B. Typical hardness is 150 HB for 7075-T651 against 95 HB for 6061, which matters for thin walls, burrs and handling damage on soft parts.

• Buy stretched stock. T651 for either alloy and T7351 for 7075 are stress relieved by stretching. An older revision of AMS 4078 notes that 7075-T7351 plate has been used typically for machined parts subject to excessive warpage during machining due to residual stresses.
• Thickness costs strength in 7075-T7351. The AMS 4078 minimums quoted above fall from about 468 MPa ultimate for plate up to 2.0 inches to 434 MPa for plate over 2.5 to 3.0 inches. Tell the shop the analysis assumes a given stock thickness.
• Do not re-age a finished 7075 part on the shop floor to fix a temper. Any re-heat treatment goes through a controlled heat treat spec; see heat treatment.
• Receiving checks. T6 and T73 stock look the same. Hardness and eddy current conductivity checks are common at receiving to catch a temper mix.

Cost and availability drivers

6061 is generally the cheaper and faster material to get, and 7075 cost climbs further when you add aerospace temper, thickness and test requirements. We do not quote material prices here; these are the drivers that move them:

• Alloy content and market. 6061 serves construction, marine, automotive and general manufacturing as well as aerospace, so mill output and service center stock are broad. 7075 demand centers on aerospace and defense plus high-strength consumer uses such as firearm receivers and bicycle parts, so the market for aerospace tempers and certified plate is narrower.
• Temper. Overaged T7351 is a narrower product than T651. Ask early whether the thickness you need exists as certified stock, because an unusual size can mean waiting for a mill run.
• Procurement spec. Asking for AMS 4078 or AMS 4045 certification rather than ASTM B209 alone narrows the eligible stock to material certified to that spec.
• Testing. Ultrasonic inspection of thick plate and specific lot testing add cost and limit sources.
• Specialty metals and origin. Aluminum is not a DFARS specialty metal, but some contracts flow down country of origin or melt source requirements; state them on the RFQ.
• Remnants and surplus. Certified drops and surplus plate with traceable mill certs can shorten lead time on small parts, provided the cert matches the drawing temper and spec.

Specifications that govern each form

Callouts usually name an AMS material spec for aerospace product, or ASTM B209 and B221 for commercial and general product. Revision letters change; confirm the current revision on ASSIST or SAE before release.

Legacy drawings may still call AMS-QQ-A-250/11 (6061 plate) or AMS-QQ-A-250/12 (7075 plate), both listed alongside AMS 4027 and AMS 4078 in distributor cross references. Do not substitute one document for another without checking that the tempers, thickness ranges and test requirements match.

Callout examples for the drawing or PO

A complete callout names alloy, temper, form, spec and any test or grain requirement, so the supplier cannot substitute stock that looks identical. Examples:

• Welded GSE frame: MATL: AL ALLOY 6061-T6 EXTRUSION PER ASTM B221. WELD PER AWS D17.1, FILLER 4043 OR 5356. Note any post-weld heat treatment.
• Machined bracket, moderate load: MATL: AL ALLOY 6061-T651 PLATE PER AMS 4027. FINISH PER MIL-PRF-8625 TYPE II CLASS 1.
• Turned fitting from bar: MATL: AL ALLOY 6061-T651 BAR PER AMS 4117.
• Highly loaded machined fitting, salt exposure: MATL: AL ALLOY 7075-T7351 PLATE PER AMS 4078. Add grain direction where lugs carry load, and plate thickness if the analysis assumed it.
• 7075-T6 where justified: MATL: AL ALLOY 7075-T651 PLATE PER AMS 4045, with the stress corrosion evaluation or approval reference required by the program.

On the PO, require a mill cert with heat or lot number, chemistry and tensile results to the named spec and revision, and confirm the cert temper matches the drawing. Our certs and traceability guide lists the full package. If the stronger steel question comes up instead, see 17-4 vs 15-5 PH stainless.

Get 6061 or 7075 material or parts quoted

Send the alloy, temper, spec, form and size you need through a certified material request. We source plate, bar and extrusion with traceable mill certs from qualified suppliers, check that the cert spec and temper match your callout before shipment, and can combine the material with machining on one PO. For stock forms, see plate and sheet, bar and rod and aluminum extrusions, or go back to the materials hub.

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Related

• Aerospace Aluminum Alloys and Tempers
• Anodizing Aluminum to MIL-PRF-8625: Engineer's Reference
• Material Certs, Specialty Metals and Lot Traceability
• 17-4 PH vs 15-5 PH Stainless Steel

Sources

• NASA MSFC-STD-3029 Revision A (February 24, 2005), stress corrosion Tables I, II and III and section 5.7 on coatings
• Protolabs, Aluminum 6061-T651/T6 material data sheet (2026)
• Continental Steel, 7075-T651 aluminum plate properties and ratings (AMS-QQ-A-250/12, ASTM B209)
• Referans Metal, AMS 4078 7075-T7351 plate minimum and typical properties
• 6061 aluminium alloy: minimum and typical T6 properties, welding, ASTM standards
• 7075 aluminium alloy: density, modulus, thermal conductivity, T7 temper
• SAE Mobilus, AMS4027 6061 T6 sheet and T651 plate
• SAE Mobilus, AMS4117L 6061 T6 and T651 bars, rods, wire and rings
• SAE Mobilus, AMS4045 7075 T6 sheet and T651 plate
• ANSI Webstore, SAE AMS4078L-2023, 7075 T73 sheet and T7351 plate
• ANSI Webstore, SAE AMS4078G-2007, historical scope note on machining warpage
• DLA ASSIST copy via ibiblio, MIL-A-8625F anodic coatings, Type III wear index