Magnesium Alloy MB8-R (Hot-rolled sheet)
Grade
As-hot-rolled thicker plate/sheet; slightly higher strength than annealed with useful ductility, common for gauges above ~4 mm.
Values for the R condition
Other MB8 tempers and conditions
MB8 is listed in 5 conditions; see the grade overview at MB8.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
MDefault Thermomechanically controlled processed | Most commonly stocked sheet condition — maximum ductility for warm forming, deep drawing and welded assemblies. | 140 | 240 | 18 | 50 HB | 25 % IACS |
Forged / die-forged condition | Hot-forged blanks for aerospace housings needing isotropic properties and elevated-temperature stability. | 150 | 250 | 12 | 52 HB | 25 % IACS |
RThis page Hot-rolled sheet | As-hot-rolled thicker plate/sheet; slightly higher strength than annealed with useful ductility, common for gauges above ~4 mm. | 155 | 250 | 14 | 53 HB | 25 % IACS |
Half-hard rolled sheet | Compromise between strength and bendability for mildly formed panels and covers. | 175 | 255 | 10 | 56 HB | 25 % IACS |
Hard rolled sheet | Highest strength / flattest thin-gauge sheet; choose for flat stiff panels that will not be formed. | 200 | 270 | 6 | 62 HB | 25 % IACS |
What is MB8-R?
MB8-R is MB8 in the R grade — as-hot-rolled thicker plate/sheet; slightly higher strength than annealed with useful ductility, common for gauges above ~4 mm. MB8-R has a yield strength of 155 MPa (22.5 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 64% of magnesium alloy grades. Elongation at break is 14% and the elastic modulus is 45 GPa (6.53 Msi). MB8-R has a density of 1.78 g/cm³ (0.0643 lb/in³), lighter than 78% of magnesium alloy grades. It melts at 645°C (1,193 °F). M is the default condition FabDigit quotes; R is available on request or by drawing note.
Advantages
- Readily welded — 85/100, better than 94% of magnesium alloy grades
- Conducts heat well — 125 W/m·K (72.2 BTU/hr·ft·°F), better than 91% of magnesium alloy grades
- Forms and bends easily — 40/100, better than 91% of magnesium alloy grades
- High service temperature — 200°C (392 °F), better than 84% of magnesium alloy grades
- Ductile — tolerates forming and impact — 14%, better than 83% of magnesium alloy grades
MB8-R properties
Typical room-temperature values for MB8-R; 20 are specific to this condition. Other listed values are MB8 reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
MB8-R has a density of 1.78 g/cm³ (0.0643 lb/in³), lighter than 78% of magnesium alloy grades. It melts at 645°C (1,193 °F).
Mechanical15
MB8-R has a yield strength of 155 MPa (22.5 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 64% of magnesium alloy grades. Elongation at break is 14% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
MB8-R is rated for continuous service to 200°C (392 °F). It conducts heat at 125 W/m·K (72.2 BTU/hr·ft·°F), better than 91% of magnesium alloy grades. Thermal expansion is 26 µm/m·K (14.4 µin/in·°F).
Electrical3
MB8-R conducts electricity at 25 % IACS, better than 69% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 64% of magnesium alloy grades.
Sustainability4
Producing a kilogram of MB8-R takes about 340 MJ of energy and emits 32 kg of CO₂ — more than 59% of magnesium alloy grades. Typical recycled content is 10%.
Manufacturability7
MB8-R's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability excellent (85/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with MB8-R
Is MB8 easy to machine?
Extremely free-cutting with high speeds, sharp positive-rake tools and no water-based coolant on fine chips; collect and control swarf as it is a fire hazard.
Can MB8 be welded?
Excellent TIG/MIG weldability with AZ61/AZ92 or matching Mg-Mn filler under argon; being Al-free it needs no post-weld stress-relief against chloride SCC.
Can MB8 be formed, bent or molded?
Cold forming is limited by the HCP structure — bend, draw and stretch at 250–350 °C with heated tooling, then air cool.
What surface finishes work on MB8?
Use chromate-free phosphate-permanganate or MAO/HAE conversion coatings followed by epoxy primer and topcoat; direct plating requires a zincate-type intermediate.
MB8 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 |
|---|---|---|
| Mnprincipal strengthening/refining addition | 1.3 – 2.2 | 1.8 |
| Ceadded as mischmetal; improves elevated-temperature strength and texture | 0.15 – 0.35 | 0.25 |
| Alimpurity limit | ≤ 0.2 | — |
| Znimpurity limit | ≤ 0.3 | — |
| Siimpurity limit | ≤ 0.1 | — |
| Cuimpurity limit | ≤ 0.05 | — |
| Feimpurity limit; controls corrosion rate | ≤ 0.05 | — |
| Niimpurity limit; controls corrosion rate | ≤ 0.01 | — |
| Others (each)total ≤ 0.30 | ≤ 0.1 | — |
| Mg | balance | — |
MB8-R — frequently asked
What is MB8-R used for?
MB8-R is typically used for laptop/phone housings, welded panels and thin-gauge stampings. In short: best-forming wrought magnesium here; no post-weld stress relief; 200 °C service ceiling.
What is the yield strength of MB8-R?
MB8-R has a typical yield strength of 155 MPa (22.5 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 64% of magnesium alloy grades. Strength varies by condition: see the 5 listed tempers.
Is MB8-R easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Extremely free-cutting with high speeds, sharp positive-rake tools and no water-based coolant on fine chips; collect and control swarf as it is a fire hazard.
Can MB8-R be welded?
Yes — weldability is rated excellent (85/100). Excellent TIG/MIG weldability with AZ61/AZ92 or matching Mg-Mn filler under argon; being Al-free it needs no post-weld stress-relief against chloride SCC.
What surface finishes work on MB8-R?
Use chromate-free phosphate-permanganate or MAO/HAE conversion coatings followed by epoxy primer and topcoat; direct plating requires a zincate-type intermediate.
Can MB8-R be formed, bent or molded?
Cold forming is limited by the HCP structure — bend, draw and stretch at 250–350 °C with heated tooling, then air cool.
What is the maximum service temperature of MB8-R?
MB8-R is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between MB8-M and MB8-Y?
M is the default condition — most commonly stocked sheet condition — maximum ductility for warm forming, deep drawing and welded assemblies. Y: highest strength / flattest thin-gauge sheet; choose for flat stiff panels that will not be formed. Yield strength is 140 MPa in M versus 200 MPa in Y.
Sources
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Magnesium) — 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.