Thick aluminum plate is not the same material in all three directions. Longitudinal is strongest, long transverse is close behind, and short transverse gives up strength, elongation and stress corrosion resistance all at once. Drop your part outline on the plate, point the load, and see exactly which direction you are loading and what it costs you.
Last updated July 2026
Drag the corner handle to resize the part, or type the dimensions above. The rolling arrows are fixed to the plate, not to the part. Every value in the graphic is repeated in the tables below.
| Direction | Ftu, ksi | Fty, ksi | Elongation, % | Kic, ksi root in | K1scc, ksi root in |
|---|---|---|---|---|---|
| L <- | 76.0 | 66.0 | 6.0 | 27 (L-T) | 25 |
| LT | 75.0 | 65.0 | 5.0 | 22 (T-L) | 20 |
| ST | 70.0 | 59.0 | 1.5 | 18 (S-L) | 5 to 8 |
Peak aging leaves the grain boundaries susceptible. The short transverse threshold is the lowest of any common aluminum plate product.
MATERIAL: 7075-T651 plate, 2.000 in thick, 48 x 96 sheet. ROLLING DIRECTION: runs along the plate length (the 96 in dimension). PART ORIENTATION: place the part with its length axis at 0° to the rolling direction. SUSTAINED LOAD AXIS: along the part length. RESOLVED GRAIN DIRECTION: L (Longitudinal), 0° to the rolling direction. SCC RATING: LOW in indoor dry, sustained load. No short transverse red flag on this orientation. BEFORE CUTTING: scribe an arrow on the remnant parallel to the rolling direction and write the alloy, temper and heat lot next to it.
All property values here are typical plate values in the mid thickness range, not guaranteed minimums. Design to the applicable AMS, ASTM B209 or MMPDS minimums and to your own certification data. Short transverse properties in particular vary with quench practice, lot and mill.
Ftu and Fty in ksi, elongation in percent, K1scc in ksi root inch measured in 3.5 percent salt alternate immersion. These are typical plate values in the mid thickness range, not guaranteed minimums. Design to the applicable AMS, ASTM B209 or MMPDS minimums.
| Alloy and temper | Thickness, in | Ftu L | Fty L | Elong L | Ftu ST | Fty ST | Elong ST | K1scc ST |
|---|---|---|---|---|---|---|---|---|
| 7075-T651 | 1.000 | 78 | 68 | 7 | 72 | 62 | 2 | 5 to 8 |
| 7075-T651 | 2.000 | 76 | 66 | 6 | 70 | 59 | 1.5 | 5 to 8 |
| 7075-T651 | 3.000 | 72 | 62 | 5 | 66 | 55 | 1 | 5 to 8 |
| 7075-T651 | 4.000 | 67 | 56 | 4 | 61 | 50 | 1 | 5 to 8 |
| 7075-T7351 | 1.000 | 70 | 60 | 8 | 66 | 55 | 3 | 25 |
| 7075-T7351 | 2.000 | 68 | 58 | 7 | 63 | 52 | 2.5 | 25 |
| 7075-T7351 | 3.000 | 66 | 56 | 6 | 61 | 50 | 2 | 25 |
| 7050-T7451 | 1.000 | 75 | 65 | 9 | 72 | 62 | 4 | 25 to 30 |
| 7050-T7451 | 2.000 | 74 | 64 | 9 | 71 | 60 | 3.5 | 25 to 30 |
| 7050-T7451 | 3.000 | 73 | 63 | 8 | 70 | 59 | 3 | 25 to 30 |
| 7050-T7451 | 4.000 | 71 | 61 | 8 | 68 | 57 | 3 | 25 to 30 |
| 7050-T7451 | 6.000 | 68 | 58 | 7 | 65 | 54 | 2.5 | 25 to 30 |
| 6061-T651 | 1.000 | 45 | 40 | 10 | 43 | 38 | 5 | above 30 |
| 6061-T651 | 3.000 | 42 | 36 | 9 | 40 | 34 | 4 | above 30 |
| 6061-T651 | 4.000 | 40 | 35 | 8 | 38 | 33 | 3 | above 30 |
| 2024-T351 | 1.000 | 68 | 47 | 12 | 62 | 42 | 4 | 6 to 9 |
| 5083-H321 | 1.000 | 46 | 33 | 12 | 44 | 31 | 6 | see note |
Read the two headline rows together. 7075-T651 gives up about 14 percent of longitudinal tensile going from 1.000 in to 4.000 in and is not normally supplied above 4.000 in at all. 7050-T7451 gives up about 9 percent all the way out to 6.000 in and holds a short transverse stress corrosion threshold of 25 to 30 ksi root inch against 5 to 8 for 7075-T651. That single comparison is why aerospace buys 7050 for thick sections.
5083-H321 note: 5xxx plate above about 3 percent magnesium is not rated by K1scc. It fails by sensitization, which is beta phase precipitation at the grain boundaries after sustained exposure above roughly 150 F, followed by intergranular attack and exfoliation. Screen it with ASTM G67, not with a grain direction threshold.
Kic is plane strain fracture toughness in ksi root inch by crack plane orientation. L-T means the crack plane is normal to L and the crack grows toward LT. K1scc is the stress intensity below which a stress corrosion crack will not propagate.
| Alloy and temper | Kic L-T | Kic T-L | Kic S-L | K1scc L | K1scc LT | K1scc ST |
|---|---|---|---|---|---|---|
| 7075-T651 | 27 | 22 | 18 | 25 | 20 | 5 to 8 |
| 7075-T7351 | 33 | 29 | 23 | 30 | 28 | 25 |
| 7050-T7451 | 38 | 33 | 28 | 30 | 28 | 25 to 30 |
| 6061-T651 | 30 or higher | not published | not published | above 30 | above 30 | above 30 |
| 2024-T351 | 34 | 30 | not published | 25 | 15 | 6 to 9 |
| 5083-H321 | not published | not published | not published | see note | see note | see note |
| Environment | Multiplier | Typical exposure |
|---|---|---|
| Indoor dry | 1.00 | Conditioned shop or enclosed assembly, no condensation |
| Humid or outdoor | 0.70 | Unconditioned storage, outdoor structure, condensing cycles |
| Marine or salt spray | 0.45 | Coastal, shipboard, de-icing salt, salt fog test |
| Chemical | 0.45 | Process exposure, cleaning chemistry, sustained chloride contact |
| Rating | K_eff, ksi root in | What it means |
|---|---|---|
| Severe | below 8 | Do not load this direction in sustained tension. Change temper or alloy. |
| High | 8 to 15 | Requires a design review, a protective system, and a stress limit well below yield. |
| Moderate | 15 to 22 | Acceptable with normal finishing and a reasonable stress margin. |
| Low | above 22 | Not a governing concern for the intended service. |
One deliberate override: the band math alone would rate 6061-T651 as high risk in a marine environment because 30 multiplied by 0.45 is 13.5. That is wrong in practice. 6061 in the T6 family is rated not susceptible to stress corrosion cracking per ASTM G64 and MIL-HDBK-5, so the tool floors it at low and tells you it did.
Theta is the angle between the part load axis and the plate rolling direction, taken from the part rotation and the rolling direction selection, then normalized to 0 to 90 degrees.
Each alloy carries Ftu, Fty and elongation at published thickness breakpoints. The tool interpolates linearly between the two breakpoints that bracket your thickness. Above the top breakpoint it holds the top value rather than extrapolating, and it says so.
The quench sensitivity penalty, measured against the thinnest published section for that alloy, in the longitudinal direction.
Computed per property at your thickness. Strength gives up a little, ductility gives up a lot.
The K1scc threshold for the alloy, temper and resolved direction is scaled by the environment multiplier, then binned. If the load is cyclic rather than sustained, the rating drops one band, because stress corrosion cracking needs a sustained tensile stress to initiate.
When the rating comes back high or severe on a T651 temper in a 7xxx alloy, the tool recommends the overaged temper and prices the trade. When the plate is thicker than 2.000 in and the alloy is 7075, it recommends 7050-T7451 and shows the property gain instead of a loss.
Short transverse is the through-thickness direction, and it is the weakest of the three. In 2 inch 7075-T651 plate, longitudinal runs about 76 ksi tensile with 6 percent elongation while short transverse runs about 70 ksi with only 1.5 percent elongation. The strength loss is modest but the ductility loss is severe, and the stress corrosion threshold collapses from about 25 ksi root inch in L to 5 to 8 in ST. Never put a sustained tensile load through the thickness of peak-aged 7075.
Check the mill markings on the long edge first, since plate is marked from the mill and the marking survives until someone cuts it up. If it is gone, look at the surface under raking light for faint parallel roll lines running along the rolling direction, or etch a small area with caustic soda and look for elongated grain streaks. A bend coupon will also crack more readily across the grain than along it. Record what you find on the traveler.
Because 7075 is quench sensitive. The alloy needs a fast quench to hold its alloying elements in solution, and the center of a thick plate cools too slowly, so the core ends up under-strengthened relative to the surface. 7075-T651 drops from about 78 ksi tensile at 1 inch to about 67 ksi at 4 inch, and it is not normally supplied above 4 inch at all. 7050 was developed specifically to fix this.
Use 7050-T7451 above about 2 inches. 7050 is far less quench sensitive, so it holds roughly 68 ksi tensile out to 6 inches where 7075-T651 has already dropped to 67 ksi at 4 inches and is unavailable beyond. 7050-T7451 also carries a short transverse stress corrosion threshold of 25 to 30 ksi root inch against 5 to 8 for 7075-T651, and higher fracture toughness. Below 2 inches, 7075-T651 is stronger and cheaper.
Because peak aging leaves the grain boundaries susceptible to stress corrosion cracking, and the short transverse direction loads those boundaries directly. The K1scc threshold in ST for 7075-T651 is only about 5 to 8 ksi root inch, so a sustained tensile stress well below yield will grow a crack in a humid or marine environment. The fix is the overaged T7351 temper, which raises the ST threshold to around 25 for roughly a 12 percent strength cost.
Much less than in 7075 or 7050. In 1 inch 6061-T651, longitudinal runs about 45 ksi tensile and short transverse about 43 ksi, a difference of only a few percent, and 6061 is not considered stress corrosion susceptible in practice. Grain direction still matters for fatigue and for forming, so honor a print callout when you get one, but 6061 will not surprise you the way peak-aged 7xxx plate does.
Once you know which direction the part has to run, you need the blank cut that way, so get an instant quote on 6061, 7075 and 7050 plate cut to your size and note the grain orientation on the order. Nox Metals supplies DFARS-compliant domestic plate with mill certs on every shipment, so the rolling direction is traceable back to the heat lot instead of guessed at on the saw.