Refractory Metal N1-RXA (Recrystallization annealed)
Heat-treated state · default condition
Standard condition for PWR fuel cladding tube: maximum ductility, lowest irradiation growth, stable creep behaviour.
Values for the RXA condition
Other N1 tempers and conditions
N1 is listed in 6 conditions; see the grade overview at N1.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RXADefaultThis page Recrystallization annealed | Standard condition for PWR fuel cladding tube: maximum ductility, lowest irradiation growth, stable creep behaviour. | 260 | 420 | 30 | 150 HB | 3.1 % IACS |
Hot rolled + annealed | General mill product form for grid straps, end plugs and machined components rather than thin-wall tube. | 270 | 430 | 28 | 152 HB | 3.1 % IACS |
beta quenched then recrystallization annealed | Beta-quench homogenizes Nb distribution before final anneal; used for pressure-tube and corrosion-optimized cladding lots. | 280 | 440 | 28 | 157 HB | 3.1 % IACS |
Partially recrystallized annealed | Intermediate strength/ductility balance used for guide tubes and some cladding designs. | 350 | 480 | 22 | 166 HB | 3.1 % IACS |
Cold worked + stress-relief annealed | Choose where higher strength and creep-collapse resistance of the tube are needed and some ductility can be traded away. | 430 | 540 | 15 | 185 HB | 3 % IACS |
Cold worked | Intermediate mill condition or hard strip/wire where maximum strength is wanted and ductility is not critical. | 540 | 620 | 9 | 17 HRC | 3 % IACS |
What is N1-RXA?
N1-RXA is N1 heat treated to RXA — standard condition for PWR fuel cladding tube: maximum ductility, lowest irradiation growth, stable creep behaviour. N1-RXA has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 68% of refractory metal grades. Elongation at break is 30% and the elastic modulus is 97 GPa (14.1 Msi). N1-RXA has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,850°C (3,362 °F).
Advantages
- Ductile — tolerates forming and impact — 30%, better than 86% of refractory metal grades
- Readily welded — 75/100, better than 81% of refractory metal grades
- Forms and bends easily — 75/100, better than 81% of refractory metal grades
- Lightweight — 6.55 g/cm³ (0.237 lb/in³), better than 77% of refractory metal grades
Limitations
- Low stiffness — 97 GPa (14.1 Msi), worse than 91% of refractory metal grades
- Low electrical conductivity — 3.1 % IACS, worse than 78% of refractory metal grades
N1-RXA properties
Typical room-temperature values for N1-RXA; 22 are specific to this condition. Other listed values are N1 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
N1-RXA has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,850°C (3,362 °F).
Mechanical16
N1-RXA has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 68% of refractory metal grades. Elongation at break is 30% and the elastic modulus is 97 GPa (14.1 Msi).
Thermal6
N1-RXA is rated for continuous service to 400°C (752 °F). It conducts heat at 18 W/m·K (10.4 BTU/hr·ft·°F), worse than 70% of refractory metal grades. Thermal expansion is 5.9 µm/m·K (3.28 µin/in·°F).
Electrical3
N1-RXA conducts electricity at 3.1 % IACS, worse than 78% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 86% of refractory metal grades.
Sustainability4
Producing a kilogram of N1-RXA takes about 1,200 MJ of energy and emits 72 kg of CO₂ — less than 51% of refractory metal grades. Typical recycled content is 10%.
Manufacturability8
N1-RXA's machinability is poor (32/100, better than 67% of refractory metal grades); weldability very good (75/100); formability very good (75/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with N1-RXA
Is N1 easy to machine?
Machine like titanium — sharp, positive-rake carbide, low speed / heavy feed, flood coolant; collect fines wet since dry chips and dust are pyrophoric.
Can N1 be welded?
GTAW or electron-beam in a high-purity argon chamber or vacuum with full back-purge; any O/N/H pickup embrittles the joint and degrades corrosion.
Can N1 be formed, bent or molded?
Cold pilgering plus intermediate vacuum anneals is the standard tube route; bend radii ≥3t cold, texture control governs irradiation growth.
What surface finishes work on N1?
Pickle in HNO3/HF then rinse thoroughly, or electropolish/autoclave-passivate to form the protective black oxide; avoid iron contamination from steel tooling.
N1 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 |
|---|---|---|
| Nbprincipal alloying element | 0.9 – 1.1 | 1 |
| Ocontrolled for strength | 0.05 – 0.12 | 0.09 |
| Fe | ≤ 0.05 | 0.03 |
| C | ≤ 0.02 | 0.01 |
| N | ≤ 0.01 | 0 |
| Hfnuclear grade — low neutron absorption | ≤ 0.01 | 0.01 |
| Si | ≤ 0.01 | — |
| Ni | ≤ 0.01 | — |
| Cr | ≤ 0.02 | — |
| H | ≤ 0 | — |
| Zr | balance | — |
N1-RXA — frequently asked
What is N1-RXA used for?
N1-RXA is typically used for fuel cladding tubes, pressure tubes and reactor structural parts. In short: domestic E110 equivalent; most formable Zr-1%Nb grade; low neutron absorption.
What is the yield strength of N1-RXA?
N1-RXA has a typical yield strength of 260 MPa (37.7 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 68% of refractory metal grades. Strength varies by condition: see the 6 listed tempers.
Is N1-RXA easy to machine?
Not especially — machinability is rated poor (32/100, better than 67% of refractory metal grades). Machine like titanium — sharp, positive-rake carbide, low speed / heavy feed, flood coolant; collect fines wet since dry chips and dust are pyrophoric.
Can N1-RXA be welded?
Yes — weldability is rated very good (75/100). GTAW or electron-beam in a high-purity argon chamber or vacuum with full back-purge; any O/N/H pickup embrittles the joint and degrades corrosion.
What surface finishes work on N1-RXA?
Pickle in HNO3/HF then rinse thoroughly, or electropolish/autoclave-passivate to form the protective black oxide; avoid iron contamination from steel tooling.
Can N1-RXA be formed, bent or molded?
Cold pilgering plus intermediate vacuum anneals is the standard tube route; bend radii ≥3t cold, texture control governs irradiation growth.
What is the maximum service temperature of N1-RXA?
N1-RXA is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between N1-RXA and N1-CW?
RXA is the default condition — standard condition for PWR fuel cladding tube: maximum ductility, lowest irradiation growth, stable creep behaviour. CW: intermediate mill condition or hard strip/wire where maximum strength is wanted and ductility is not critical. Yield strength is 260 MPa in RXA versus 540 MPa in CW.
Sources
- ASTM B811 Standard Specification for Wrought Zirconium Alloy Seamless Tubes for Nuclear Reactor Fuel Cladding — ASTM International (2019)
- ASTM B350/B350M Zirconium and Zirconium Alloy Ingots for Nuclear Application — ASTM International (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Zirconium and Hafnium) — ASM International (1990)
- IAEA TECDOC series on zirconium alloy fuel cladding behaviour and thermophysical properties — IAEA (2010)
- Zr-1Nb (E110/M5-type) cladding tube technical data — nuclear zirconium tube producers (2022)
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.