Refractory Metal M5-CW (Cold worked)
Supply condition
Use only as an intermediate as-pilgered hollow, where strength peaks at 620 MPa yield / 700 MPa tensile with 8% elongation; residual stress and texture are unadjusted, so it is not a final delivery condition.
Values for the CW condition
Other M5 tempers and conditions
M5 is listed in 5 conditions; see the grade overview at M5.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Beta-quenched | Specify as a process intermediate: the beta quench refines the structure and homogenises Nb distribution before final cold tube reduction and recrystallisation, giving the best corrosion microstructure. | 310 | 450 | 28 | 170 HB | 3 % IACS |
RXADefault Fully recrystallized annealed | Pick the fully recrystallized annealed state for PWR fuel cladding tubes: best corrosion, irradiation growth and creep behaviour with 30% elongation, at the lowest strength of 330 MPa yield. | 330 | 470 | 30 | 165 HB | 3.1 % IACS |
Partially recrystallized annealed | Use the partially recrystallized annealed state for spacer grid straps and some structural tubing, giving 420 MPa yield with more ductility and creep margin than the stress-relieved condition. | 420 | 530 | 20 | 184 HB | 3.1 % IACS |
Cold worked and stress-relief annealed | Choose cold worked and stress-relief annealed material for guide tubes and structural members needing 500 MPa yield at operating temperature, accepting lower ductility and creep resistance. | 500 | 590 | 15 | 198 HB | 3.1 % IACS |
CWThis page Cold worked | Use only as an intermediate as-pilgered hollow, where strength peaks at 620 MPa yield / 700 MPa tensile with 8% elongation; residual stress and texture are unadjusted, so it is not a final delivery condition. | 620 | 700 | 8 | 21 HRC | 3 % IACS |
What is M5-CW?
M5-CW is M5 supplied in the CW condition — use only as an intermediate as-pilgered hollow, where strength peaks at 620 MPa yield / 700 MPa tensile with 8% elongation; residual stress and texture are unadjusted, so it is not a final delivery condition. M5-CW has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 84% of refractory metal grades. Elongation at break is 8% and the elastic modulus is 98 GPa (14.2 Msi). M5-CW has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,840°C (3,344 °F). RXA is the default condition FabDigit quotes; CW is available on request or by drawing note.
Advantages
- High strength — 620 MPa (89.9 ksi), better than 84% of refractory metal grades
- Lightweight — 6.55 g/cm³ (0.237 lb/in³), better than 77% of refractory metal grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 95% of refractory metal grades
- Low stiffness — 98 GPa (14.2 Msi), worse than 84% of refractory metal grades
- Low electrical conductivity — 3 % IACS, worse than 81% of refractory metal grades
- Poor heat conductor — 17 W/m·K (9.82 BTU/hr·ft·°F), worse than 79% of refractory metal grades
- Limited ductility — 8%, worse than 75% of refractory metal grades
M5-CW properties
Typical room-temperature values for M5-CW; 23 are specific to this condition. Other listed values are M5 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
M5-CW has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,840°C (3,344 °F).
Mechanical16
M5-CW has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 84% of refractory metal grades. Elongation at break is 8% and the elastic modulus is 98 GPa (14.2 Msi).
Thermal6
M5-CW is rated for continuous service to 300°C (572 °F). It conducts heat at 17 W/m·K (9.82 BTU/hr·ft·°F), worse than 79% of refractory metal grades. Thermal expansion is 5.8 µm/m·K (3.22 µin/in·°F).
Electrical3
M5-CW conducts electricity at 3 % IACS, worse than 81% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is very good (80/100), worse than 54% of refractory metal grades.
Sustainability4
Producing a kilogram of M5-CW takes about 1,250 MJ of energy and emits 80 kg of CO₂ — more than 52% of refractory metal grades. Typical recycled content is 15%.
Manufacturability8
M5-CW's machinability is poor (25/100, worse than 65% of refractory metal grades); weldability good (60/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M5-CW
Is M5 easy to machine?
Run low speed with heavy feed using sharp carbide tooling and ample water-based coolant. Chips form a combustible powder that must be collected separately; never grind or machine dry.
Can M5 be welded?
Use GTAW, electron-beam or laser welding (typical for end-plug closures) in a vacuum chamber or under full inert-gas shielding. Trace oxygen, nitrogen or hydrogen contamination causes embrittlement — an acceptable weld must stay bright silver.
Can M5 be formed, bent or molded?
Tube is made from extruded hollows by multi-pass cold pilgering with intermediate vacuum anneals. Room-temperature forming needs generous bend radii to avoid twin cracking and to control springback.
What surface finishes work on M5?
HNO3/HF pickling for decontamination followed by polishing is standard. The protective oxide forms in service, so plating and coatings are normally omitted; remove all fluoride residues.
M5 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 |
|---|---|---|
| Nbmain alloying element; forms β-Nb precipitates | 0.8 – 1.2 | 1 |
| Osolid-solution strengthening, tightly controlled | 0.09 – 0.15 | 0.13 |
| Fecontrolled trace addition | 0.02 – 0.06 | 0.04 |
| Strace S improves creep resistance | 8×10⁻⁴ – 0 | 0 |
| SnSn-free design (residual only) | ≤ 0.01 | 0.01 |
| C | ≤ 0.02 | 0.01 |
| N | ≤ 0.01 | 0 |
| Hfnuclear grade: Hf removed to lower neutron absorption | ≤ 0.01 | 0.01 |
| Cr | ≤ 0.02 | 0.01 |
| Ni | ≤ 0.01 | 0 |
| Zr | balance | — |
M5-CW — frequently asked
What is M5-CW used for?
M5-CW is typically used for PWR fuel rod cladding, fuel assembly guide tubes, fuel rod end plugs, spacer grid strip and nuclear fuel assembly components. In short: lowest-corrosion Zr-Nb cladding; low in-reactor hydrogen pickup; high ductility, 30% elongation.
What is the yield strength of M5-CW?
M5-CW has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 84% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is M5-CW easy to machine?
Not especially — machinability is rated poor (25/100, worse than 65% of refractory metal grades). Run low speed with heavy feed using sharp carbide tooling and ample water-based coolant. Chips form a combustible powder that must be collected separately; never grind or machine dry.
Can M5-CW be welded?
Yes — weldability is rated good (60/100). Use GTAW, electron-beam or laser welding (typical for end-plug closures) in a vacuum chamber or under full inert-gas shielding. Trace oxygen, nitrogen or hydrogen contamination causes embrittlement — an acceptable weld must stay bright silver.
What surface finishes work on M5-CW?
HNO3/HF pickling for decontamination followed by polishing is standard. The protective oxide forms in service, so plating and coatings are normally omitted; remove all fluoride residues.
Can M5-CW be formed, bent or molded?
Tube is made from extruded hollows by multi-pass cold pilgering with intermediate vacuum anneals. Room-temperature forming needs generous bend radii to avoid twin cracking and to control springback.
What is the maximum service temperature of M5-CW?
M5-CW is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between M5-RXA and M5-CW?
RXA is the default condition — pick the fully recrystallized annealed state for PWR fuel cladding tubes: best corrosion, irradiation growth and creep behaviour with 30% elongation, at the lowest strength of 330 MPa yield. CW: use only as an intermediate as-pilgered hollow, where strength peaks at 620 MPa yield / 700 MPa tensile with 8% elongation; residual stress and texture are unadjusted, so it is not a final delivery condition. Yield strength is 330 MPa in RXA versus 620 MPa in CW.
Sources
- ASTM B811 — Wrought Zirconium Alloy Seamless Tubes for Nuclear Reactor Fuel Cladding — ASTM International (2021)
- ASTM B350/B350M — Zirconium and Zirconium Alloy Ingots for Nuclear Application — ASTM International (2022)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Zirconium) — ASM International (1990)
- Thermophysical Properties of Materials for Nuclear Engineering (Zr alloys) — IAEA (2008)
- M5 fuel cladding alloy technical publications — Framatome (AREVA NP) (2018)
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.