Cast and sintered AlNiCo magnets for instruments, sensors and high-temperature magnetic circuits where flux stability over temperature matters more than maximum coercivity.
Cast and sintered AlNiCo magnets for instruments, sensors and high-temperature magnetic circuits where flux stability over temperature matters more than maximum coercivity.
AlNiCo remains valuable because its reversible temperature coefficient is exceptionally low and its Curie temperature is high. The trade-off is low coercivity, which makes geometry and the magnetic circuit unusually important.
| Application | Typical Spec | Why this material |
|---|---|---|
| Precision instruments | Alnico 2 / 5 | Very low flux drift over temperature |
| Watt-hour meters | Alnico 5 | Long-term stable reference field |
| Reed switch actuation | Alnico 3 / 5 | Stable actuation across temperature |
| Radar / TWT / instruments | Alnico 8 / 9 | High-temperature stability |
| Educational / scientific | Alnico 2 | Classic rods / horseshoe forms |
| Route | Strength | Tolerance / shape logic | Typical use |
|---|---|---|---|
| Cast | Higher energy and complex castable forms | Larger geometry; grinding on functional surfaces | Horseshoes, meters, sensors, instruments |
| Sintered | Fine grain and repeatability for small parts | Smaller precision components | Miniature sensors, magnetic circuits, instruments |
Because coercivity is low, final magnetic stability must be checked in the real geometry/circuit rather than inferred from Br alone.
Use the table as a selection reference. Final acceptance limits follow the approved drawing/specification and agreed test method.
| Grade / Route | Br | Hc | Hci | (BH)max | Max Operating Temp* |
|---|---|---|---|---|---|
| Alnico 2 (Sintered) | 7.0 kG / 0.70 T | 500 Oe / 40 kA/m | ≥540 Oe / 43 kA/m | 1.5 MGOe / 12 kJ/m³ | 450°C |
| Alnico 5 (Sintered) | 11.0 / 1.10 | 600 / 48 | ≥600 / 48 | 4.25 / 34 | 450°C |
| Alnico 8 (Sintered) | 8.8 / 0.88 | 1530 / 121 | ≥1600 / 127 | 5.25 / 42 | 450°C |
| Alnico 5 (Cast) | 12.2 / 1.22 | 600 / 48 | 630 / 50 | 5.0 / 40 | 500°C |
| Alnico 5B (Cast) | 12.2 / 1.22 | 650 / 52 | 660 / 53 | 5.5 / 44 | 500°C |
| Alnico 5DG (Cast) | 12.5 / 1.25 | 690 / 55 | 700 / 56 | 6.5 / 52 | 500°C |
| Alnico 5-7 (Cast) | 13.0 / 1.30 | 700 / 56 | 740 / 59 | 7.5 / 60 | 525°C |
| Alnico 8-HC (Cast) | 7.0 / 0.70 | 1750 / 139 | 1750 / 139 | 4.5 / 36 | 525°C |
| Alnico 8 (Cast) | 8.2 / 0.82 | 1500 / 119 | 1600 / 127 | 5.0 / 40 | 525°C |
| Alnico 8B (Cast) | 8.8 / 0.88 | 1500 / 119 | 1650 / 131 | 5.5 / 44 | 525°C |
| Alnico 8C (Cast) | 9.0 / 0.90 | 1380 / 110 | 1440 / 115 | 7.5 / 60 | 525°C |
| Alnico 9 (Cast) | 10.5 / 1.05 | 1410 / 112 | 1440 / 139 | 9.0 / 72 | 525°C |
Higher magnetic performance and complex near-net-shape geometries such as horseshoes, rods and special flux paths.
Better suited to smaller precision parts with tighter as-produced geometry and fine grain structure.
AlNiCo can demagnetize in short magnetic lengths. High L/D or a suitable steel magnetic circuit should be evaluated before finalizing geometry.
For many designs, magnetization after assembly helps preserve the intended working point.
| Property | Sintered | Cast |
|---|---|---|
| Vickers hardness | ~440 | 440–620 |
| Density | 6.8–7.0 g/cm³ | 6.9–7.3 g/cm³ |
| Curie temperature | 810–860°C | 740–860°C |
| Specific resistance | 50–70 μΩ·cm | 45–75 μΩ·cm |
| Thermal expansion | 11.0–12.4 ×10⁻⁶/°C | 11.0–13.0 ×10⁻⁶/°C |
| Reversible temperature coefficient Br | ≈ −0.02 to −0.03%/°C | ≈ −0.02 to −0.03%/°C |
| Route | Typical Tolerance | Notes |
|---|---|---|
| As-cast | ±0.3–0.5 mm | Economical near-net shape |
| Ground | ±0.05 mm | Pole and mounting faces |
| Sintered | ±0.05 mm | Small precision parts |
| Machining | Grinding-focused | Hard/brittle alloy; functional surfaces are normally ground |
Cast and sintered product families start from different forming routes.
Thermal processing establishes the magnetic phase and directional properties.
Functional dimensions and surfaces are ground or finished to drawing.
Parts can be magnetized in-house or supplied unmagnetized depending on the customer assembly route.
Where required, controlled stabilization can reduce later field drift.
Dimensions and magnetic output are verified to the agreed method.
CoA / magnetic-property results can include Br, Hcb, Hcj and (BH)max according to the agreed inspection plan.
Gauge, optical inspection or CMM/3D optical measurement can be used according to geometry and critical dimensions.
Before shipment, we can provide a real-time inspection video showing the product, equipment, measurement process and actual displayed data for remote customer verification.
FAI / PPAP / RoHS / REACH / traceability documents are available according to project and customer requirements.
All technical PDFs in this library are hosted locally on empiremagnets.com and use the current Ningbo Empire document identity and revision format.
Its exceptionally low reversible temperature coefficient makes it valuable in meters, sensors and instruments where field stability matters more than compact size.
AlNiCo has relatively low coercivity, so the magnetic working point depends strongly on shape and circuit. Short shapes can self-demagnetize.
Cast AlNiCo can be produced in shapes that would be difficult to build from brittle rare-earth segments, including horseshoes and specialized flux paths.
Many AlNiCo designs benefit from magnetization in the final magnetic circuit. The correct method depends on assembly and field requirements.
