Refractory Metal Mo-La-SR (Stress relieved)
Heat-treated state
ASTM B387 Grade 364 · GB MoLa · also Lanthanated Molybdenum
Pick when flatness and low residual stress matter for machined or laser-cut parts, with only a small strength penalty.
Values for the SR condition
Other Mo-La tempers and conditions
Mo-La is listed in 5 conditions; see the grade overview at Mo-La.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
powder-metallurgy blank, not worked | Cheapest form for crucibles, blanks and machined-from-solid parts where residual porosity and low ductility are acceptable. | 300 | 380 | 3 | 171 HB | 26 % IACS |
Recrystallized / fully annealed | Represents the property floor after long high-temperature service; ML keeps a fine elongated grain structure so it stays far tougher than recrystallized pure Mo. | 310 | 450 | 22 | 160 HB | 33 % IACS |
SRThis page Stress relieved | Pick when flatness and low residual stress matter for machined or laser-cut parts, with only a small strength penalty. | 490 | 640 | 13 | 17 HRC | 31 % IACS |
As RolledDefault worked and stress-relieved sheet/plate (default supply) | Standard stocked condition for ML sheet, plate and foil: highest as-supplied strength with usable room-temperature bend ductility. | 560 | 700 | 8 | 21 HRC | 30 % IACS |
Swaged / Forged Rod | Standard ML rod and bar condition for electrodes, stirrers, pins and machined furnace hardware. | 600 | 750 | 18 | 22 HRC | 30 % IACS |
What is Mo-La-SR?
Mo-La-SR is Mo-La heat treated to SR — pick when flatness and low residual stress matter for machined or laser-cut parts, with only a small strength penalty. Mo-La-SR has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 75% of refractory metal grades. Elongation at break is 13% and the elastic modulus is 320 GPa (46.4 Msi). Mo-La-SR has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 63% of refractory metal grades. It melts at 2,620°C (4,748 °F). As Rolled is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- High service temperature — 1,700°C (3,092 °F), better than 90% of refractory metal grades
- High electrical conductivity — 31 % IACS, better than 86% of refractory metal grades
- Stiff — 320 GPa (46.4 Msi), better than 84% of refractory metal grades
- Conducts heat well — 125 W/m·K (72.2 BTU/hr·ft·°F), better than 84% of refractory metal grades
- Low embodied carbon — 25 kg CO₂/kg, better than 80% of refractory metal grades
Mo-La-SR properties
Typical room-temperature values for Mo-La-SR; 23 are specific to this condition. Other listed values are Mo-La reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Mo-La-SR has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 63% of refractory metal grades. It melts at 2,620°C (4,748 °F).
Mechanical17
Mo-La-SR has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 75% of refractory metal grades. Elongation at break is 13% and the elastic modulus is 320 GPa (46.4 Msi).
Thermal6
Mo-La-SR is rated for continuous service to 1,700°C (3,092 °F). It conducts heat at 125 W/m·K (72.2 BTU/hr·ft·°F), better than 84% of refractory metal grades. Thermal expansion is 5.3 µm/m·K (2.94 µin/in·°F).
Electrical3
Mo-La-SR conducts electricity at 31 % IACS, better than 86% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 72% of refractory metal grades.
Sustainability4
Producing a kilogram of Mo-La-SR takes about 380 MJ of energy and emits 25 kg of CO₂ — less than 78% of refractory metal grades. Typical recycled content is 25%.
Manufacturability7
Mo-La-SR's machinability is fair (38/100, better than 90% of refractory metal grades); weldability poor (22/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Mo-La-SR
Is Mo-La easy to machine?
Machine with sharp positive-rake carbide or PCD at moderate speed and generous feed, flood coolant, and preheat/warm the part for tapping or thin-wall turning to avoid chipping and edge cracking.
Can Mo-La be welded?
Only EB or laser welding in high vacuum/inert gas is practical, and the fusion zone recrystallizes and becomes notch-sensitive — vacuum brazing or mechanical fastening is preferred for load-bearing joints.
Can Mo-La be formed, bent or molded?
Roll, bend and deep-draw warm (about 150–400 °C for sheet, higher for thick stock); keep bend radii ≥3–5 t, and avoid grinding-induced surface cracks that trigger brittle failure.
What surface finishes work on Mo-La?
Chemically clean/pickle or electropolish for vacuum service; for air service above ~500 °C apply a silicide (Si-Mo) or CVD/plasma-sprayed oxidation barrier — plating and anodizing are not used.
Mo-La 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 |
|---|---|---|
| La2O3lanthana dispersoid; common commercial blends are 0.3 %, 0.7 % (Plansee ML) and 1.1 % | 0.3 – 1.2 | 0.7 |
| Cimpurity limit | ≤ 0.01 | 0.01 |
| Oexcluding oxygen bound in La₂O₃ | ≤ 0.03 | — |
| Feimpurity limit | ≤ 0.01 | — |
| Niimpurity limit | ≤ 0.01 | — |
| Siimpurity limit | ≤ 0.01 | — |
| Mo≥98.8 % balance | balance | — |
Mo-La-SR — frequently asked
What is Mo-La-SR used for?
Mo-La-SR is typically used for furnace heating elements, sapphire crystal-growth crucibles, sputtering targets and backing plates, hot-zone shields and support structures, hot-work tooling for glass and metal forming and drawn wire for high-temperature leads and springs. In short: ductile-improved molybdenum wire.
What is the yield strength of Mo-La-SR?
Mo-La-SR has a typical yield strength of 490 MPa (71.1 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 75% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is Mo-La-SR easy to machine?
Not especially — machinability is rated fair (38/100, better than 90% of refractory metal grades). Machine with sharp positive-rake carbide or PCD at moderate speed and generous feed, flood coolant, and preheat/warm the part for tapping or thin-wall turning to avoid chipping and edge cracking.
Can Mo-La-SR be welded?
Not readily — weldability is rated poor (22/100). Only EB or laser welding in high vacuum/inert gas is practical, and the fusion zone recrystallizes and becomes notch-sensitive — vacuum brazing or mechanical fastening is preferred for load-bearing joints.
What surface finishes work on Mo-La-SR?
Chemically clean/pickle or electropolish for vacuum service; for air service above ~500 °C apply a silicide (Si-Mo) or CVD/plasma-sprayed oxidation barrier — plating and anodizing are not used.
Can Mo-La-SR be formed, bent or molded?
Roll, bend and deep-draw warm (about 150–400 °C for sheet, higher for thick stock); keep bend radii ≥3–5 t, and avoid grinding-induced surface cracks that trigger brittle failure.
What is the maximum service temperature of Mo-La-SR?
Mo-La-SR is rated for continuous use to about 1,700°C (3,092 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Mo-La As Rolled and Mo-La-RX?
As Rolled is the default condition — standard stocked condition for ML sheet, plate and foil: highest as-supplied strength with usable room-temperature bend ductility. RX: represents the property floor after long high-temperature service; ML keeps a fine elongated grain structure so it stays far tougher than recrystallized pure Mo. Yield strength is 560 MPa in As Rolled versus 310 MPa in RX.
Sources
- Molybdenum-Lanthanum Oxide (ML) material property data — Plansee SE (2023)
- ASTM B386/B386M — Molybdenum and Molybdenum Alloy Plate, Sheet, Strip and Foil — ASTM International (2021)
- ASTM B387 — Molybdenum and Molybdenum Alloy Bar, Rod and Wire — ASTM International (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- Lanthanated molybdenum sheet, rod and wire product data — Elmet Technologies / Ed Fagan / (2024)
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.