Aluminum 6351
AA 6351 · UNS A96351 · EN AW-6351, AW 6351
6351 is a medium-strength heat-treatable Al–Mg–Si–Mn extrusion alloy, essentially a manganese-bearing, higher-silicon relative of 6061/6082 that develops Mg2Si strengthening on ageing.
6351 tempers and conditions
6351 is supplied in 11 conditions, soft to hard.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Slightly strain hardened | Soft, near-annealed 6351 with only incidental strain hardening from handling/straightening — maximum formability, lowest strength. | 70 | 130 | 22 | 35 HB | 50 % IACS |
Annealed | Fully softened condition for maximum bending, drawing or severe forming before re-solution treatment and ageing. | 75 | 150 | 25 | 42 HB | 50 % IACS |
Cooled from hot working and naturally aged | As-extruded 6351 quenched on the press and naturally aged — moderate strength with good ductility and formability before any artificial ageing. | 100 | 180 | 20 | 55 HB | 44 % IACS |
Cooled from hot working, naturally aged, stress relieved by… | T1 press-quenched and naturally aged 6351 that has been straightened/stress relieved, giving T1-level strength with tighter straightness and lower residual stress. | 105 | 185 | 19 | 57 HB | 44 % IACS |
Solution heat treated and naturally aged | Pick when the part must be bent or formed after heat treatment and then aged to T6, or where moderate strength with good ductility is enough. | 150 | 250 | 20 | 65 HB | 40 % IACS |
Cooled from hot working and artificially aged | Press-quenched and aged directly on the extrusion line — cheapest route to near-T6 strength in thin sections with good straightness. | 260 | 295 | 12 | 90 HB | 45 % IACS |
T5, stress relieved by stretching | Use where T5 strength is wanted but residual stress and distortion during machining must be minimised. | 260 | 295 | 11 | 90 HB | 45 % IACS |
Cooled from hot working, cold worked in the die, artificially aged | Specialised press temper for close-tolerance profiles that receive sizing work in the die before ageing. | 265 | 300 | 10 | 92 HB | 45 % IACS |
Solution heat treated and artificially aged | Default structural condition: peak strength with acceptable ductility for extruded frames, tubes, brackets and machined parts. | 285 | 310 | 14 | 95 HB | 44 % IACS |
Solution treated, stress-relieved by stretching, aged, no further… | Choose for long extruded profiles that will be heavily machined and must stay dimensionally stable. | 285 | 310 | 13 | 95 HB | 44 % IACS |
T6, stress relieved by stretching, minor straightening | Same as T6510 but with a small amount of final straightening allowed; the usual stocked temper for precision bar and tube. | 285 | 310 | 13 | 95 HB | 44 % IACS |
What is 6351?
6351 is a medium-strength heat-treatable Al–Mg–Si–Mn extrusion alloy, essentially a manganese-bearing, higher-silicon relative of 6061/6082 that develops Mg2Si strengthening on ageing. It is chosen for structural extrusions, tubing, road-transport and marine framing where good strength, weldability and corrosion resistance are needed at moderate cost. Limits: it loses strength in the weld heat-affected zone, is not usable much above ~150 °C, and older 6351 pressure-cylinder stock showed susceptibility to sustained-load cracking, so it has largely been replaced by 6061/6082 in gas-cylinder service. 6351 has a density of 2.71 g/cm³ (0.0979 lb/in³), heavier than 51% of aluminum grades. It melts at 555°C (1,031 °F). 6351 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 310 MPa (45 ksi) — stronger than 73% of aluminum grades. Elongation at break is 14% and the elastic modulus is 69 GPa (10 Msi).
What is 6351 used for?
- Pressure pipe
- Truck rails
- Cylinders
Advantages
- Conducts heat well — 176 W/m·K (101.7 BTU/hr·ft·°F), better than 86% of aluminum grades
- High electrical conductivity — 44 % IACS, better than 85% of aluminum grades
- Ductile — tolerates forming and impact — 14%, better than 81% of aluminum grades
6351 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
6351 has a density of 2.71 g/cm³ (0.0979 lb/in³), heavier than 51% of aluminum grades. It melts at 555°C (1,031 °F).
Mechanical12
6351 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 310 MPa (45 ksi) — stronger than 73% of aluminum grades. Elongation at break is 14% and the elastic modulus is 69 GPa (10 Msi).
Thermal6
6351 is rated for continuous service to 150°C (302 °F). It conducts heat at 176 W/m·K (101.7 BTU/hr·ft·°F), better than 86% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
6351 conducts electricity at 44 % IACS, better than 85% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), better than 67% of aluminum grades.
Sustainability4
Producing a kilogram of 6351 takes about 210 MJ of energy and emits 12.5 kg of CO₂ — more than 88% of aluminum grades. Typical recycled content is 30%.
Manufacturability8
6351's machinability is good (62/100, better than 55% of aluminum grades); weldability very good (78/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 6351 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 6351
Is 6351 easy to machine?
Machines well in T5/T6 with sharp polished-flute carbide tools, high speed and flood or MQL lubrication; T4/O tempers are gummy and produce built-up edge.
Can 6351 be welded?
Readily GMAW/GTAW welded with 4043 or 5356 filler, but the HAZ over-ages to roughly T4-level strength — design joints for reduced properties or re-heat-treat and age.
Can 6351 be formed, bent or molded?
Extrudes at moderate press speeds (slower than 6063 owing to Mn and Si); bend in O or T4 and age afterwards, since T6 tolerates only generous bend radii.
Manufacturability
The process limits FabDigit applies to 6351. Every 6351 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better62 / 100 |
|---|---|
| ISO material group | N.1 |
| Cutting speed (rough / finish) | 350 / 420 m/min |
| Minimum wall | 0.5 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 8× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better45 / 100 |
|---|---|
| Weldability | Better78 / 100 |
6351 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Si | 0.7 – 1.3 | 1 |
| Mg | 0.4 – 0.8 | 0.6 |
| Mngrain-structure control, distinguishes 6351 from 6061 | 0.4 – 0.8 | 0.6 |
| Fe | ≤ 0.5 | 0.25 |
| Cu | ≤ 0.1 | 0.03 |
| Zn | ≤ 0.2 | 0.05 |
| Ti | ≤ 0.2 | 0.02 |
| Others (each) | ≤ 0.05 | |
| Others (total) | ≤ 0.15 | |
| Al | balance |
What surface finishes work on 6351?
Takes clear and hard anodising well and accepts chromate/chrome-free conversion coating, powder coat and paint; the Mn-bearing structure gives a greyer anodic film than 6063.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Conversion Coating
PVD Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 6351 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 6351 cost?
6351 is a budget-cost aluminum ($), cheaper than about 82% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
6351 — frequently asked
What is 6351 used for?
6351 is typically used for pressure pipe, truck rails and cylinders. In short: pressure-tube extrusion.
What is the yield strength of 6351?
6351 has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 310 MPa (45 ksi) — stronger than 73% of aluminum grades. Strength varies by condition: see the 11 listed tempers.
Is 6351 easy to machine?
Reasonably — machinability is rated good (62/100, better than 55% of aluminum grades). Machines well in T5/T6 with sharp polished-flute carbide tools, high speed and flood or MQL lubrication; T4/O tempers are gummy and produce built-up edge.
Can 6351 be welded?
Yes — weldability is rated very good (78/100). Readily GMAW/GTAW welded with 4043 or 5356 filler, but the HAZ over-ages to roughly T4-level strength — design joints for reduced properties or re-heat-treat and age.
What surface finishes work on 6351?
Takes clear and hard anodising well and accepts chromate/chrome-free conversion coating, powder coat and paint; the Mn-bearing structure gives a greyer anodic film than 6063.
Can 6351 be formed, bent or molded?
Extrudes at moderate press speeds (slower than 6063 owing to Mn and Si); bend in O or T4 and age afterwards, since T6 tolerates only generous bend radii.
What is the maximum service temperature of 6351?
6351 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 6351 cost?
6351 is a budget-cost aluminum ($), cheaper than about 82% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 6351?
Yes — 6351 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- EN 755-2 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Mechanical properties — CEN (2016)
- ASTM B221 Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes — ASTM (2021)
- ASM Handbook Vol. 2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol. 13B: Corrosion — Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.