Magnesium Alloy MB1-O (Annealed)
Temper · default condition
Softest, most formable condition — pick for press-brake/hot-formed sheet parts and welded assemblies.
Values for the O condition
Other MB1 tempers and conditions
MB1 is listed in 5 conditions; see the grade overview at MB1.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ODefaultThis page Annealed | Softest, most formable condition — pick for press-brake/hot-formed sheet parts and welded assemblies. | 105 | 225 | 12 | 40 HB | — |
Hot rolled sheet/plate | Economical heavier-gauge plate for machined tooling plates and jigs; intermediate strength, no final anneal. | 140 | 240 | 9 | 45 HB | 33 % IACS |
As fabricated | Standard supply condition for extruded MB1 stock — best all-round strength/ductility balance for machined parts. | 165 | 250 | 12 | 44 HB | — |
Strain hardened and partially annealed, half hard | Pick when higher sheet strength/stiffness-per-gauge is needed and only mild forming is required. | 180 | 255 | 6 | 48 HB | — |
as forged / die-forged condition | Choose for hot die-forged brackets and housings where flow-line strength and near-net shape matter. | 180 | 260 | 10 | 47 HB | 33 % IACS |
What is MB1-O?
MB1-O is MB1 in the O temper — softest, most formable condition — pick for press-brake/hot-formed sheet parts and welded assemblies. MB1-O has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 87% of magnesium alloy grades. Elongation at break is 12% and the elastic modulus is 45 GPa (6.53 Msi). MB1-O has a density of 1.76 g/cm³ (0.0636 lb/in³), lighter than 94% of magnesium alloy grades. It melts at 648°C (1,198 °F).
Advantages
- Readily welded — 90/100, better than 99% of magnesium alloy grades
- Conducts heat well — 138 W/m·K (79.7 BTU/hr·ft·°F), better than 98% of magnesium alloy grades
- High electrical conductivity — 33 % IACS, better than 97% of magnesium alloy grades
- Forms and bends easily — 35/100, better than 87% of magnesium alloy grades
Limitations
- Hard to polish — 45/100, worse than 93% of magnesium alloy grades
- Low strength — 105 MPa (15.2 ksi), worse than 87% of magnesium alloy grades
MB1-O properties
Typical room-temperature values for MB1-O; 11 are specific to this condition. Other listed values are MB1 reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
MB1-O has a density of 1.76 g/cm³ (0.0636 lb/in³), lighter than 94% of magnesium alloy grades. It melts at 648°C (1,198 °F).
Mechanical12
MB1-O has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 87% of magnesium alloy grades. Elongation at break is 12% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
MB1-O is rated for continuous service to 150°C (302 °F). It conducts heat at 138 W/m·K (79.7 BTU/hr·ft·°F), better than 98% of magnesium alloy grades. Thermal expansion is 26 µm/m·K (14.4 µin/in·°F).
Electrical3
MB1-O conducts electricity at 33 % IACS, better than 97% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), worse than 57% of magnesium alloy grades.
Sustainability4
Producing a kilogram of MB1-O takes about 300 MJ of energy and emits 28 kg of CO₂ — less than 92% of magnesium alloy grades. Typical recycled content is 25%.
Manufacturability7
MB1-O's machinability is excellent (93/100, worse than 78% of magnesium alloy grades); weldability excellent (90/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with MB1-O
Is MB1 easy to machine?
Machines faster and with lower power than any other structural metal — use sharp, high-rake tools, dry or with mineral oil (never water-based coolant), and keep fine chips wet/contained because they are a fire hazard.
Can MB1 be welded?
Excellent GTAW/GMAW weldability with AZ61A/EZ33 or matching Mg-Mn filler under argon; being aluminium-free it is not prone to weld-zone SCC and post-weld stress relief is usually unnecessary.
Can MB1 be formed, bent or molded?
Cold formability is limited by the HCP structure — bend and draw at 230–350 °C with generous radii; extrusion and hot forging behave well at 300–400 °C.
What surface finishes work on MB1?
Always apply chemical conversion (chromate-free per ASTM D1732), Dow 17/HAE anodizing or PEO plus epoxy primer; isolate from steel/brass/carbon-fibre fasteners to avoid galvanic corrosion.
MB1 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 |
|---|---|---|
| MnGB/T 5153 MB1; ASTM M1A specifies Mn 1.2 min | 1.3 – 2.5 | 1.8 |
| Alimpurity limit | ≤ 0.2 | — |
| Znimpurity limit | ≤ 0.3 | — |
| Siimpurity limit | ≤ 0.1 | — |
| Feimpurity limit; strongly affects corrosion | ≤ 0.05 | — |
| Cuimpurity limit | ≤ 0.05 | — |
| Niimpurity limit; strongly affects corrosion | ≤ 0.01 | — |
| Caper ASTM M1A | ≤ 0.3 | — |
| Others (total) | ≤ 0.3 | — |
| Mg | balance | — |
MB1-O — frequently asked
What is MB1-O used for?
MB1-O is typically used for welded sheet structures, extruded profiles and fuel tanks. In short: most weldable wrought magnesium; aluminium-free, no weld SCC; lower strength than AZ31.
What is the yield strength of MB1-O?
MB1-O has a typical yield strength of 105 MPa (15.2 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 87% of magnesium alloy grades. Strength varies by condition: see the 5 listed tempers.
Is MB1-O easy to machine?
Yes — machinability is rated excellent (93/100, worse than 78% of magnesium alloy grades). Machines faster and with lower power than any other structural metal — use sharp, high-rake tools, dry or with mineral oil (never water-based coolant), and keep fine chips wet/contained because they are a fire hazard.
Can MB1-O be welded?
Yes — weldability is rated excellent (90/100). Excellent GTAW/GMAW weldability with AZ61A/EZ33 or matching Mg-Mn filler under argon; being aluminium-free it is not prone to weld-zone SCC and post-weld stress relief is usually unnecessary.
What surface finishes work on MB1-O?
Always apply chemical conversion (chromate-free per ASTM D1732), Dow 17/HAE anodizing or PEO plus epoxy primer; isolate from steel/brass/carbon-fibre fasteners to avoid galvanic corrosion.
Can MB1-O be formed, bent or molded?
Cold formability is limited by the HCP structure — bend and draw at 230–350 °C with generous radii; extrusion and hot forging behave well at 300–400 °C.
What is the maximum service temperature of MB1-O?
MB1-O 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.
What is the difference between MB1-O and MB1-H24?
O is the default condition — softest, most formable condition — pick for press-brake/hot-formed sheet parts and welded assemblies. H24: pick when higher sheet strength/stiffness-per-gauge is needed and only mild forming is required. Yield strength is 105 MPa in O versus 180 MPa in H24.
Sources
- ASTM B90/B90M Magnesium-Alloy Sheet and Plate — ASTM (2015)
- ASTM B107/B107M Magnesium-Alloy Extruded Bars, Rods, Profiles, Tubes — ASTM (2013)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.