6061 vs 7075 Aluminum: Strength, Cost, and Machinability Compared (with Selection Rules)

6061 vs 7075 aluminum is a yield strength decision before it is a cost decision. 6061-T6 has a typical yield of 276 MPa (40 ksi) and 7075-T6 has a typical yield of 503 MPa (73 ksi) in the T6 condition per ASM Handbook Vol. 2.

7075-T6 carries 82% more yield strength than 6061-T6. Fracture toughness runs the other way. 6061-T651 plate measures 29.1 MPa√m against 22.5 MPa√m for 7075-T651, both T-L orientation, bend specimens at 24 °C. The stronger alloy is the less crack tolerant one.

This guide covers the five gates that decide the alloy, the data behind each gate per ASTM B209/B209M-21a and ASM Handbook Vol. 2, three cost baselines, machining behavior on the spindle, and the stock forms you can order. For choosing between variants inside 6061, see the 6061 aluminum properties and selection guide.

1. 6061 vs 7075 in five gates

Five-Gate Alloy Selection runs 6061 as the default and escalates to 7075 only when a gate blocks it. The five gates are load, joining, finish, environment, and cost, run in that order. Cost sits last because pricing both alloys before the load case is settled produces a number you cannot act on.

6061 clears the load gate on most machined brackets and housings, because the 35.0 ksi (240 MPa) minimum yield per ASTM B209/B209M-21a Table 4 sits above the working stress of a part that was sized for stiffness. Stiffness does not move with alloy choice. Elastic modulus in tension is 68.9 GPa for 6061 and 71.0 GPa for 7075, a 3% gap per ASM Handbook Vol. 2. A part that deflects too far needs a thicker wall or a better section shape, and a 7075 upgrade will not fix it.

Each gate has one job, which is to prove that 6061 cannot do the work. Gates two through four disqualify 7075 outright in specific service conditions, so a part can fail gate one and still return to 6061 after gate two or gate three.

Engineering note. Run the gates in order even when the budget is fixed. With a working stress above the 35.0 ksi (240 MPa) yield minimum and an envelope that still has room, thickening a 6061 section costs less than switching alloys, because 6061 bar has traded near 37% of 7075 bar cost at the same 1.25 in diameter and removes with lower tool wear. The exception is a weight-capped part such as a drone airframe, where added section defeats the design intent and gate one hands the part to 7075 at once.

Table 1. Five-Gate Alloy Selection quick reference

1. Load	Peak working stress and fatigue stress from FEA or hand calculation	Working stress above the 35.0 ksi (240 MPa) specification minimum yield, or fatigue stress above 97 MPa (14 ksi) at 5 x 10⁸ cycles	Stay on 6061-T6	Move to 7075-T6, then re-run gates 2 to 4 before committing
2. Joining	Whether any structural joint needs fusion welding	Any load-carrying fusion weld in the assembly	Stay on 6061-T6 and design for the weakened heat affected zone	7075 is out. Redesign the joint as fastened or bonded, or return to 6061
3. Finish	Whether the part needs repeatable Class 2 color anodize	Cosmetic color match required across a production batch	Stay on 6061-T6	7075 is out for cosmetic color. Type III hardcoat on 7075 stays open
4. Environment	Sustained tensile stress combined with chloride exposure	Salt air, marine, or chloride service under sustained load	Stay on 6061-T6	Specify 7075-T73 and accept 434 MPa (63 ksi) yield instead of 503 MPa (73 ksi)
5. Cost	Material price, cycle time, and tool wear together	Evaluated only on alloys that cleared gates 1 to 4	Quote 6061-T6	Quote 7075 and name the gate that forced it in the drawing note

2. 6061 vs 7075 composition and what it decides

Copper and zinc separate these two alloys and set four of the five gates. 6061 carries 0.15 to 0.40% copper and 0.25% zinc maximum. 7075 carries 1.20 to 2.0% copper and 5.1 to 6.1% zinc, per ASTM B209/B209M-21a Table 1 and ASM Handbook Vol. 2.

Zinc and magnesium do the strengthening work in 7075. They form MgZn₂ precipitates during solution treatment and artificial aging, and that is where the 503 MPa (73 ksi) yield comes from. 6061 strengthens through Mg₂Si precipitates instead, built from 0.8 to 1.2% magnesium and 0.40 to 0.8% silicon. Two different strengthening systems, two different ceilings. No heat treatment moves 6061 into 7075 territory.

Copper above 1% is what closes gates 2 and 3 on 7075. In a fusion weld pool, the copper and zinc widen the freezing range and promote liquation cracking. In the anodize tank, copper dissolves out of the surface and leaves an uneven oxide that shifts color batch to batch. Both effects come from the chemistry, so no welding procedure change and no bath control removes them. The full element and property comparison sits in Table 2, and the wider materials and properties reference covers the other alloys in the same decision.

Engineering note. Specify 6061-T6 when one part carries both a structural weld and a color anodize requirement, even when the load case points at 7075. Splitting the assembly into a welded 6061 subframe and a fastened 7075 load member adds one interface and two part numbers, and that cost lands below the cost of requalifying a cracked weld. The exception is a single-piece machined part with no joint and no cosmetic face, where gates 2 and 3 do not fire and the decision returns to load and price.

3. 6061 vs 7075 strength, fatigue, and fracture toughness

7075-T6 wins on yield and fatigue and loses on fracture toughness. 7075-T6 yields at 503 MPa (73 ksi) against 276 MPa (40 ksi) for 6061-T6, and reaches 159 MPa (23 ksi) fatigue strength against 97 MPa (14 ksi), both at 5 x 10⁸ cycles on R.R. Moore rotating beam tests.

6061-T651 plate reverses that ranking at 29.1 MPa√m plane strain fracture toughness against 22.5 MPa√m for 7075-T651, both T-L orientation, bend specimens at 24 °C, per ASM Handbook Vol. 2 Table 12.

The fracture toughness reversal changes which failure mode you design against. 6061-T651 tolerates 29% more crack driving force before unstable fracture, so a part that sees impact, has a stress raiser it cannot remove, or lives with a known crack from service damage is not automatically better in 7075. A part sized against a static yield limit still is.

Orientation matters more in 7075 than most drawings admit. Average KIC in 7075-T651 plate runs 28.6 MPa√m in L-T, 24.2 MPa√m in T-L, and 17.6 MPa√m in S-L per ASM Handbook Vol. 2 Table 109. The short transverse value sits 38% below the longitudinal one. Machine a part out of thick plate with its main tensile direction through the thickness and the toughness you designed with is not the toughness you get.

Weight is where 7075 earns its place. Density is 2.70 g/cm³ for 6061 and 2.80 g/cm³ for 7075, so 7075 adds 3.7% mass while adding 82% yield. Calculated from the ASM tensile and density values, specific strength runs 115 kN·m/kg for 6061-T6 and 204 kN·m/kg for 7075-T6. On a mass-capped part, that 78% gain in strength per unit mass is the entire argument.

Every number above is a T6 or T651 value. Ordering the wrong temper moves the yield you designed with, and the 6061 temper differences (T6 vs T651) decide how much the part moves after machining. Yield minimums also differ from the ASM typical values shown here, which is why the tolerances and standards you call out drive acceptance, not the handbook figure.

Engineering note. With a fatigue-driven part under a fixed mass budget, 7075-T6 is the correct call because its 159 MPa (23 ksi) endurance value at 5 x 10⁸ cycles is 64% above 6061-T6 and mass cannot be traded for section. With a fatigue-driven part that has room to grow, thickening 6061 lowers the stress amplitude faster than the alloy change raises the limit, at lower material and tooling cost. This stops being true once the added section pushes the part outside its envelope or past the stock thickness range in Section 7.

Table 2. 6061-T6 and 7075-T6 side by side

Composition	Copper	0.15 to 0.40%	1.20 to 2.0%	ASTM B209/B209M-21a Table 1; ASM Vol. 2	Gates 2, 3, 4
Composition	Zinc	0.25% max	5.1 to 6.1%	ASTM B209/B209M-21a Table 1; ASM Vol. 2	Gates 1, 3
Composition	Magnesium	0.8 to 1.2%	2.1 to 2.9%	ASTM B209/B209M-21a Table 1; ASM Vol. 2	Gate 1
Composition	Silicon	0.40 to 0.8%	0.40% max	ASTM B209/B209M-21a Table 1; ASM Vol. 2	Gate 1
Mechanical	Tensile strength	310 MPa (45 ksi)	572 MPa (83 ksi)	ASM Vol. 2, typical T6 values	Gate 1
Mechanical	Yield strength	276 MPa (40 ksi)	503 MPa (73 ksi)	ASM Vol. 2, typical T6 values	Gate 1
Mechanical	Elongation	12% at 1.6 mm sheet, 17% at 13 mm bar	11%	ASM Vol. 2	Gate 1
Mechanical	Shear strength	207 MPa (30 ksi)	331 MPa (48 ksi)	ASM Vol. 2	Gate 1
Mechanical	Hardness	95 HB	150 HB	ASM Vol. 2, 500 kg load, 10 mm ball, 30 s	Gate 1
Mechanical	Fatigue strength	97 MPa (14 ksi)	159 MPa (23 ksi)	ASM Vol. 2, 5 x 10⁸ cycles, R.R. Moore	Gate 1
Mechanical	Fracture toughness KIC	29.1 MPa√m (T651 plate)	22.5 MPa√m (T651 plate)	ASM Vol. 2 Table 12, T-L, bend, 24 °C	Gate 1
Mechanical	Elastic modulus, tension	68.9 GPa	71.0 GPa	ASM Vol. 2	Not a gate. Stiffness is a geometry problem
Mechanical	Density	2.70 g/cm³	2.80 g/cm³	ASM Vol. 2 at 20 °C	Gate 1
Mechanical	Specific strength, UTS per density	115 kN·m/kg	204 kN·m/kg	Calculated from ASM Vol. 2 values	Gate 1
Mechanical	Thermal conductivity	167 W/m·K at 25 °C	130 W/m·K at 20 °C	ASM Vol. 2	Heat sinks and cold plates
Cost	Distributor price premium	Baseline	60 to 90% above 6061	Published distributor comparison	Gate 5
Cost	Bar stock purchase ratio	Baseline	About 2.66x at 1.25 in diameter	Same-day quotes, 1000 lb and up bracket, machinist forum record	Gate 5
Cost	EPOC finished part ratio	[PENDING EPOC DATA]	[PENDING EPOC DATA]	[PENDING EPOC DATA]	Gate 5
Machinability	Chip formation	Longer, more ductile chips	Chips break shorter and cleaner	Shop practice, expanded in Section 5	Gate 5
Machinability	Carbide tool wear	Lower	Higher at the same parameters	Shop practice, expanded in Section 5	Gate 5
Machinability	As-machined finish	Built-up edge risk on finishing passes	Brighter as-machined surface	Shop practice, expanded in Section 5	Gate 5
Joining and finish	Fusion welding	Weldable, heat affected zone loses temper	Not suited to structural fusion welding	Section 6	Gate 2
Joining and finish	Class 2 color anodize	Repeatable across batches	Color shifts with copper content	MIL-A-8625F, Section 6	Gate 3
Joining and finish	Chloride service under sustained load	Suitable	Specify T73 and accept 434 MPa (63 ksi) yield	ASM Vol. 2	Gate 4

4. The three cost baselines for 7075

7075 costs more at three baselines, and the three numbers disagree because the denominators differ. Published distributor comparisons put the premium at 60 to 90%. A same-day bar stock record puts it at 2.66x. Finished part price lands below both.

The distributor baseline compares list price per pound, alloy against alloy. It ignores product form, diameter, and quantity bracket, which is why it reads as a wide band instead of a number. Use it for a first pass and stop there.

The purchase baseline is tighter because it holds the variables. One machinist record covers ten bars of 1.25 in diameter stock quoted on the same day at the 1000 lb and up bracket: 6061-T6 at 38 USD per bar against 7075-T6 at 101 USD per bar. That is 2.66x, or a 166% premium. It is still material only.

The finished part baseline is the one you quote against, and material is one line in it. Take a machined part where material carries 30% of the quoted price. A 2.66x material cost raises the part price by about 50%. Drop the material share to 15% and the same alloy change raises the part by about 25%. The alloy premium compresses as machining, finishing, and inspection content grows.

Engineering note. Quote the alloy change against the finished part price when the part has heavy feature content, because the material line is diluted and the premium lands closer to 25% than 166%. Quote it against the purchase baseline when the part is milled from solid, because you buy the full block and material dominates. The exception is rapid prototyping at single-digit quantities, where setup and programming carry the price. That reverses in low volume production once setup amortizes across the batch.

5. 6061 vs 7075 on the machine

7075 does not cut worse than 6061 in the way published ratings suggest. Shop records report that 7075 chips break shorter, the as-machined surface comes off brighter, and the same speeds and feeds carry over from 6061. What changes is carbide life.

Published machinability ratings disagree with each other. One metals supplier rates 6061 as good and 7075 as fair. Another rates both as good. Neither scale reports a measured tool life or a surface roughness value, so both are opinions in a table cell. Work from cutting behavior instead.

7075 sits at 150 HB against 95 HB for 6061 and is slightly more abrasive to a carbide edge. Chips break into short pieces and clear the pocket without nesting, and finishing passes come off brighter without a dedicated skim cut. The cost of 7075 shows up in tool consumption and edge replacement intervals, not in cycle time.

6061 is the more ductile of the two at 12 to 17% elongation against 11% for 7075. That ductility produces longer chips and a built-up edge risk on finishing passes, which shows as smearing and size drift instead of a broken tool. Surface speed, chip load, and chip evacuation control it, and the finishing pass you land on also sets the Ra you carry into the tank, covered in the surface finish you must leave before anodize the surface finish you must leave before anodize.

“On the same thin-wall drone bracket, with one carbide end mill and no change to speed, feed, depth of cut, or coolant, we average 120 parts per cutting edge in 6061-T6 and about 75 in 7075-T6. That puts the tool change interval at roughly 63 percent of the 6061 figure. Flank wear accelerates and the cutting edge begins to micro-chip, because 7075 is harder and loads the contact zone more heavily. The edge gives out first. The cycle time barely moves.” —Dewey Wu, General Manager and senior mechanical engineer, EPOC CRAFTER

Engineering note. Budget for shorter carbide life on 7075 at the same parameters you run on 6061, because the higher hardness and the abrasive constituents attack the edge instead of the cycle. Keep the 6061 program and step the tool change interval in. The exception is a thin wall or a long unsupported feature, where 7075 lets you hold the same deflection at a thinner section and the shorter chips reduce recutting, so cycle time can fall even as tooling cost rises. Both cases are checked at the quote stage, not after the first article.

6. Where 7075 stops being an option

7075 fails gate 2 and gate 3 outright and passes gate 4 only in an over-aged temper. Copper at 1.20 to 2.0% and zinc at 5.1 to 6.1% drive all three outcomes, and no welding procedure change and no anodize bath adjustment removes them.

6.1 Gate 2, fusion welding

7075 is not suited to structural fusion welding. Zinc and copper widen the freezing range of the weld pool, which promotes liquation cracking along grain boundaries in the partially melted zone. The failure appears after welding, not during it, so a visually sound joint can still be cracked. Fastened and adhesive-bonded joints are the design answer for 7075 assemblies.

6061 welds, and the cost lands on the joint strength you are allowed to use. Design the weld region against the T4 minimum instead of the T6 minimum. ASTM B209/B209M-21a Table 4 lists 16.0 ksi (110 MPa) yield minimum for T4 against 35.0 ksi (240 MPa) for T6, a 54% reduction across the joint. In the fully annealed worst case the ceiling drops further: AMS4025P caps the O condition at 12.0 ksi (83 MPa) yield and 22.0 ksi (152 MPa) tensile, which is 34% of the T6 yield minimum.

Post-weld recovery exists on paper and rarely survives contact with a fabricated assembly. AMS4027P requires the material to develop full properties after solution heat treatment and aging to T62 per AMS2772, with no subsequent cold working or forming. A welded frame quenched from solution temperature distorts, and straightening it is the cold work the specification excludes. Size the joint for T4 and skip the argument.

6.2 Gate 3, color anodize

6061 takes repeatable Class 2 color anodize and 7075 does not. MIL-A-8625F defines Class 1 as undyed and Class 2 as dyed, across Type I chromic, Type II sulfuric, and Type III hard anodic coatings. Copper dissolves preferentially in the anodizing electrolyte, and at 1.20 to 2.0% in 7075 against 0.15 to 0.40% in 6061 the oxide grows less uniformly and the dyed result shifts from lot to lot. The mechanism is compositional, so bath control does not fix it.

Type III hardcoat stays open on 7075 where the requirement is wear and not appearance. MIL-A-8625F gives a Type III thickness range of 0.0005 to 0.0045 in with 0.002 in applying when the drawing states nothing else, against 0.00007 to 0.0010 in for Type II. Type III shall not be sealed when maximum abrasion resistance is the primary function, which is the trade you accept against corrosion performance.

Corrosion acceptance for Type I and Type II runs 336 h of ASTM B117 salt spray with specimens inclined 6 degrees. Coating selection, dimensional growth allowances, and drawing callout format sit in the pre-anodize sizing guide for 6061, the pre-anodize sizing guide for 6061, and the process runs through surface finishing.

6.3 Gate 4, chloride service under sustained load

7075-T6 in the peak-aged condition is susceptible to stress corrosion cracking under sustained tensile stress in chloride environments. The remedy is the T73 over-aged temper, and it costs strength while returning three things. Yield drops from 503 MPa (73 ksi) to 434 MPa (63 ksi), a 14% loss. Thermal conductivity rises from 130 to 155 W/m·K, a 19% gain. Electrical conductivity rises from 33% to 40% IACS. Plane strain fracture toughness rises from 24.2 MPa√m average in T651 to 31.9 MPa√m average in T7351, both T-L orientation in plate, per ASM Handbook Vol. 2 Table 109.

Read the T73 numbers next to the 6061 numbers before you commit. 7075-T73 at 434 MPa (63 ksi) yield still sits 57% above the 6061-T6 typical value of 276 MPa (40 ksi) and 81% above the ASTM B209 minimum of 240 MPa (35.0 ksi). The over-aged temper gives up strength and keeps the entire reason you left 6061.

Engineering note. Specify 7075-T73 instead of 7075-T6 whenever the part carries a sustained tensile load in salt air, because the 14% yield loss buys a 32% fracture toughness gain and removes the failure mode that the higher yield cannot protect against. Specify 7075-T6 when the load is cyclic or intermittent and the part lives indoors, since sustained stress is the condition the cracking mechanism requires. The exception is a part that also needs a cosmetic face, where gate 3 has already ended the discussion and the choice returns to 6061-T6.

7. 6061 stock forms and thickness limits

A specification minimum and a handbook typical value are two different numbers, and mixing them is the most common error in alloy comparisons. 6061-T6 shows 276 MPa (40 ksi) yield in ASM Handbook Vol. 2 and a 35.0 ksi (240 MPa) minimum in ASTM B209/B209M-21a Table 4, a 13% gap. Design and accept against the minimum.

The same gap runs through tensile strength. ASM lists 45 ksi typical against a 42.0 ksi B209 minimum, a 6.7% spread. Every published 6061 versus 7075 comparison table you will find online, including Table 2 above, reports handbook typical values for both alloys. Those tables are correct for ranking the alloys and wrong for sizing a part.

7.1 Sheet and plate

ASTM B209/B209M-21a does not define a thickness boundary between sheet and plate. Temper availability does the job instead. T6 covers 0.006 to 0.249 in and T651 covers 0.250 to 6.000 in, so the temper on your drawing already constrains the thickness you can buy. Ordering 6061-T6 plate at 0.500 in thickness is not an order the standard supports.

Strength tapers at the top of the T651 range. Tensile minimum holds at 42.0 ksi through 4.000 in and drops to 40.0 ksi from 4.001 to 6.000 in, with the SI table showing 290 MPa through 100.00 mm and 275 MPa from over 100.00 through 150.00 mm. Elongation minimum falls further across the same span, from 10% at 0.250 to 0.499 in, to 9% through 1.000 in, to 8% through 2.000 in, to 6% through 6.000 in. A thick plate part is less ductile than the same alloy in sheet, at the same T6 strength callout.

Two tempers on the B209 table are not orderable. The standard states directly that T42 and T62 material is not available from the material producer, so both appear as heat treatment response requirements and not as supply conditions.

7.2 Bar and rod

ASTM B211-03 covers rolled and cold-finished bar, rod, and wire. T6, T62, and T651 all carry 42.0 ksi tensile minimum, 35.0 ksi yield minimum, and 10% elongation minimum from 0.125 to 8.000 in, with bar limited to a 50 in² maximum cross-sectional area. Rod up to 3 in diameter and bar up to 2 in thick with a maximum rectangle width of 4 in must be supplied cold finished, so surface condition on small sizes is a standard requirement and not a shop option.

B211 carries a third path that alloy comparison articles skip. Tempers T89 and T94 reach 54.0 ksi tensile minimum and 47.0 ksi yield minimum at 0.374 in diameter and under. That is 34% more yield than 6061-T6 for a small-diameter part, without leaving 6061 and without paying the 7075 premium. Pins, shafts, standoffs, and threaded studs under 0.374 in are the natural candidates.

7.3 Extrusions

ASTM B221-02 covers extruded bar, rod, wire, profiles, and tubes, and the same T6 callout buys less strength here. T6, T62, T6510, and T6511 carry 38.0 ksi tensile minimum against the 42.0 ksi minimum for sheet, plate, bar, and rod, a 9.5% reduction for an identical drawing note. Yield minimum holds at 35.0 ksi. Elongation minimum runs 8% up through 0.249 in wall and 10% at 0.250 in and over, so the thicker extrusion is the more ductile one, which reverses the plate behavior above.

Product form definitions carry a dimensional threshold worth knowing at drawing stage. B221 defines an extruded bar as having at least one perpendicular distance between parallel faces of 0.375 in or greater, and an extruded rod as 0.375 in diameter or greater. Below that, the product is wire and a different property row applies.

7.4 When ASTM is not enough

ASTM B211-03 does not define the stress-relief stretch amount for T651. It states only that a stress-relieved temper is not required to match the basic temper in characteristics other than those specified. AMS4027P does define it: solution heat treat, stretch to a nominal permanent set of 1-1/2% to 3%, then precipitation heat treat per AMS2772. A drawing that needs a quantified stress-relief operation calls out AMS4027P and not ASTM alone. How much the part then moves on the table is the subject of 6061 temper differences (T6 vs T651).

AMS4027P was revised 2022-04 and covers 0.006 to 6.000 in as T6 sheet and T651 plate. AMS4025P was revised 2025-07 and covers the annealed O condition at 0.006 to 3.000 in, capped at 22.0 ksi tensile and 12.0 ksi yield. Both supersede their N revisions, and citing the letter suffix on a drawing is what makes the callout auditable.

Engineering note. Call out the product form alongside the temper on every 6061 drawing, because an extruded profile marked 6061-T6 is accepted at 38.0 ksi tensile minimum and a machined plate part marked the same way is accepted at 42.0 ksi. Call out the standard and its revision letter for a qualified program, since AMS4027P quantifies the T651 stretch that ASTM B211-03 leaves open. The exception is a low-stress bracket where the safety factor already covers the 4.0 ksi spread. Both are checked during DFM design guidelines review.

Table 3. 6061 specification minimums by product form

Sheet	ASTM B209/B209M-21a Table 4	T6, T62	0.006 to 0.249 in	42.0 ksi (290 MPa)	35.0 ksi (240 MPa)	4% to 10% by thickness	Thin sections lose ductility, not strength
Plate	ASTM B209/B209M-21a Table 4	T62, T651	0.250 to 4.000 in	42.0 ksi (290 MPa)	35.0 ksi (240 MPa)	10% down to 6%	The standard sets no sheet to plate boundary. Temper availability does
Plate, heavy	ASTM B209/B209M-21a Table 4	T651	4.001 to 6.000 in	40.0 ksi (275 MPa)	35.0 ksi (240 MPa)	6%	Tensile minimum drops 2.0 ksi above 4 in
Bar, rod, wire	ASTM B211-03 Table 2	T6, T62, T651	0.125 to 8.000 in	42.0 ksi	35.0 ksi	10%	Bar capped at 50 in² cross-section. Rod to 3 in and bar to 2 in must be cold finished
Bar, rod, wire	ASTM B211-03 Table 2	T89, T94	0.374 in and under	54.0 ksi	47.0 ksi	Not specified	34% more yield than T6 without leaving 6061
Extruded bar, rod, profile, tube	ASTM B221-02 Table 2	T6, T62, T6510, T6511	Up through 0.249 in wall	38.0 ksi	35.0 ksi	8%	Same T6 callout, 9.5% lower tensile acceptance
Extruded bar, rod, profile, tube	ASTM B221-02 Table 2	T6, T62, T6510, T6511	0.250 in and over	38.0 ksi	35.0 ksi	10%	Thicker extrusion is the more ductile one
Sheet and plate, aerospace	AMS4027P, revised 2022-04	T6 sheet, T651 plate	0.006 to 6.000 in	42.0 ksi to 4.000 in, 40.0 ksi above	35.0 ksi	10% down to 6%	Defines T651 stretch at 1-1/2% to 3% permanent set per AMS2772
Sheet and plate, annealed	AMS4025P, revised 2025-07	O	0.006 to 3.000 in	22.0 ksi max	12.0 ksi max	10% to 18%	Maximums, not minimums. This is the annealed ceiling

8. Five gates applied to real parts

The five gates land on a specific alloy for each part class, and the gate that fires is the one you write in the drawing note. Table 4 runs the eight part types that generate most 6061 and 7075 quotes.

Two alloys sit outside this comparison and get pulled in by mistake. 6063 is the extrusion and appearance grade, with lower strength than 6061 and a better as-extruded surface, so it belongs to architectural profiles and enclosure frames and does not enter the load gate. 5052 is the sheet metal grade, non heat treatable and formable, so it belongs to bent brackets and chassis panels made on a sheet metal line. Neither is a substitute for a machined 6061 part under load.

Table 4. Five gates applied to eight part types

Structural bracket, moderate load	6061-T6	Gate 1 clears	Working stress sits under the 35.0 ksi (240 MPa) B209 yield minimum, and 6061 removes with lower tool wear
Consumer electronics enclosure	6061-T6	Gate 3 blocks 7075	Class 2 color anodize must repeat across a batch, which copper at 1.20 to 2.0% prevents
Welded structural assembly	6061-T6	Gate 2 blocks 7075	7075 cracks in the partially melted zone. Size the 6061 joint at the 16.0 ksi (110 MPa) T4 minimum
Drone airframe	7075-T6	Gate 1 blocks 6061	Mass is capped, so section cannot be added. 204 kN·m/kg specific strength against 115 for 6061
Bike parts, high stress	7075-T6	Gate 1 blocks 6061	Fatigue at 159 MPa (23 ksi) against 97 MPa (14 ksi) at 5 x 10⁸ cycles decides the frame and crank members
Aircraft structure	7075-T6 or T73	Gates 1 and 4	T6 for internal dry members. T73 at 434 MPa (63 ksi) yield where sustained load meets salt air
Firearm receiver	7075-T6	Gate 1 blocks 6061	High cyclic and impact load in a mass-limited envelope, fastened and pinned, not welded
Optical mount, impact exposed	6061-T651	Gate 1 clears on toughness	29.1 MPa√m against 22.5 MPa√m fracture toughness. The stronger alloy is the wrong answer here

Engineering note. Choose the alloy on the gate that fires first and put that gate in the drawing note, because a note reading “7075-T6 required, mass-limited envelope” survives a design review and a bare “7075-T6” invites a value engineering challenge on every quote cycle. The exception is a part where two gates fire in opposite directions, such as a mass-limited part that also needs color anodize, in which case the finish requirement wins and the mass budget gets solved with geometry. Call before that drawing is released.

8.1 Choose 6061 when

• Working stress stays under the 35.0 ksi (240 MPa) B209 yield minimum with your safety factor applied
• Any joint in the assembly carries load through a fusion weld
• The part needs repeatable Class 2 color anodize across a production batch
• The part sees impact, carries a stress raiser you cannot design out, or lives in chloride service under sustained load

8.2 Choose 7075 when

• FEA or hand calculation puts working stress above the 6061 yield minimum and the envelope has no room for a thicker section
• Mass is capped and the 204 kN·m/kg specific strength gain is the design intent
• Fatigue stress exceeds 97 MPa (14 ksi) at 5 x 10⁸ cycles and section cannot be traded
• All joints are fastened or bonded, the finish is Type III hardcoat or a dark Class 2 shade, and gates 2 through 4 are clear

Run the four items in each list against your own part before you release the drawing. The Five-Gate Alloy Selection Checklist puts the same sequence on one page with the specification minimums, the three cost baselines, and the stock form limits, and it is built to sit next to a print during design review. Download it, run your part through it, and send the file with your CNC machining request for quote so the material review starts from the gate that decided your alloy.

Download the Five-Gate Alloy Selection Checklist

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9. Frequently asked questions

Is 6061 stronger than 7075?

7075 is the stronger alloy on every strength measure. 7075-T6 reaches 503 MPa (73 ksi) yield and 572 MPa (83 ksi) tensile against 276 MPa (40 ksi) and 310 MPa (45 ksi) for 6061-T6, per ASM Handbook Vol. 2 typical values. Hardness runs 150 HB against 95 HB at a 500 kg load with a 10 mm ball. 6061 reverses the ranking on fracture toughness, where T651 plate measures 29.1 MPa√m against 22.5 MPa√m for 7075-T651 in the T-L orientation. Strength and crack tolerance are separate properties, and a part that fails by cracking instead of by yielding is better served by 6061.

Which is easier to machine, 6061 or 7075?

Both machine well, and the difference shows in tool life instead of cycle time. Shop records report that 7075 chips break shorter and clear a pocket without nesting, the as-machined surface comes off brighter, and the same speeds and feeds carry over from 6061. What 7075 costs you is carbide edge life, since it sits at 150 HB against 95 HB and is slightly more abrasive. 6061 runs the longer chip because of its higher ductility at 12 to 17% elongation, which creates a built-up edge risk on finishing passes. Published good and fair machinability ratings report neither tool life nor surface roughness, so treat them as opinions.

Is 7075 worth the extra cost?

7075 is worth the premium when a gate blocks 6061 and not before. The premium reads differently at three baselines. Distributor list comparisons show 60 to 90%. One same-day bar stock record at 1.25 in diameter and the 1000 lb bracket shows 2.66x, at 38 USD against 101 USD per bar. On a finished part where material carries 30% of the quoted price, that 2.66x material ratio raises the part by about 50%, and at a 15% material share it raises the part by about 25%. Heavy feature content dilutes the premium. Solid-block parts with high stock removal do not.

Can you weld 7075 aluminum?

7075 is not suited to structural fusion welding. Zinc at 5.1 to 6.1% and copper at 1.20 to 2.0% widen the freezing range of the weld pool and promote liquation cracking in the partially melted zone, and the cracking appears after the joint has cooled, so a visually sound weld can still be defective. Fastened, pinned, and adhesive-bonded joints are the correct design approach for 7075 assemblies. 6061 welds, at the cost of the strength you are allowed to claim across the joint. Design the weld region against the 16.0 ksi (110 MPa) T4 yield minimum instead of the 35.0 ksi (240 MPa) T6 minimum.

When should I use 7075 instead of 6061?

Use 7075 when your load case exceeds the 6061 yield minimum and the envelope cannot absorb a thicker section. Four conditions justify the switch. Working stress above 35.0 ksi (240 MPa) with no room to grow the section. A mass cap where the 204 kN·m/kg specific strength against 115 for 6061 is the design intent. Fatigue stress above 97 MPa (14 ksi) at 5 x 10⁸ cycles. All joints fastened or bonded with no structural weld. If the part also needs repeatable color anodize or lives under sustained load in chloride service, 7075-T6 is disqualified and the choice returns to 6061 or to 7075-T73.

Which alloy has better fracture toughness, 6061 or 7075?

6061 has the higher fracture toughness, which reverses the strength ranking. 6061-T651 plate measures 29.1 MPa√m plane strain fracture toughness against 22.5 MPa√m for 7075-T651, both T-L orientation bend specimens at 24 °C per ASM Handbook Vol. 2 Table 12. 6061 tolerates 29% more crack driving force before unstable fracture. Orientation matters more in 7075, where average KIC in T651 plate runs 28.6 MPa√m in L-T, 24.2 MPa√m in T-L, and 17.6 MPa√m in S-L. The short transverse value sits 38% below the longitudinal one, so a thick-plate part loaded through the thickness gets less toughness than the datasheet suggests.

What thickness of 6061 plate can I order in T651?

T651 covers 0.250 to 6.000 in per ASTM B209/B209M-21a, and the temper on your drawing constrains the thickness you can buy. T6 covers 0.006 to 0.249 in, so 6061-T6 at 0.500 in is not an order the standard supports. Strength tapers at the top of the T651 range. Tensile minimum holds at 42.0 ksi (290 MPa) through 4.000 in and drops to 40.0 ksi (275 MPa) from 4.001 to 6.000 in. Elongation minimum falls from 10% at 0.250 to 0.499 in, to 9% through 1.000 in, to 8% through 2.000 in, and to 6% at 6.000 in. A thick plate part is less ductile at the same T6 strength callout, so check elongation before you specify heavy plate.

When should I specify 7075-T73 instead of 7075-T6?

Specify T73 when the part carries sustained tensile load in a chloride environment. 7075-T6 in the peak-aged condition is susceptible to stress corrosion cracking under those conditions, and the over-aged T73 temper removes the failure mode. Yield drops from 503 MPa (73 ksi) to 434 MPa (63 ksi), a 14% loss. Fracture toughness rises from 24.2 MPa√m average in T651 to 31.9 MPa√m average in T7351 in the T-L orientation. Thermal conductivity rises from 130 to 155 W/m·K and electrical conductivity from 33% to 40% IACS. T73 at 434 MPa still sits 81% above the 6061 yield minimum, so the reason you left 6061 survives the downgrade.

This guide is the alloy selection article in the EPOC CRAFTER 6061 aluminum cluster. It sits below the 6061 properties and grades guide and links across to the temper selection article and the machining and anodizing article listed below.

Related Resources

Related Article: 6061 Aluminum Properties and Grades. Which 6061 variant to specify before you compare alloys.

Related Article: 6061-T6 vs T651 vs T6511. Which temper to order to keep the part from moving after machining.

Related Article: Machining 6061 for Anodize. Pre-anodize dimensions, surface finish, and masking decisions.

Related Capability: CNC Machining. 3-axis and 5-axis milling and turning for 6061 and 7075 parts from prototype through low volume production.

Related Material Guide: Materials and Properties. Specification minimums and machining behavior across the metals and plastics in the same decision.