Cobalt-based magnet alloys are high-performance magnetic materials engineered for high coercivity, excellent thermal stability, strong magnetic energy density, and long-term dimensional stability. They outperform ferrite and many rare-earth magnets in harsh thermal and mechanical environments.
What Are Cobalt-Based Magnet Alloys?
These alloys use cobalt as a primary magnetic element due to its high Curie temperature, strong magnetic anisotropy, and superior thermal stability.
| Magnet Type | Key Features |
|---|---|
| Alnico | High flux density, excellent temperature stability |
| Samarium–Cobalt (SmCo) | High coercivity, high-temperature capability |
| Cobalt–Iron (Co–Fe) | Very high saturation magnetization |
Chemical Composition
| Element | Typical Range (wt%) |
|---|---|
| Cobalt | 5 – 35 |
| Aluminum | 8 – 12 |
| Nickel | 15 – 30 |
| Iron | Balance |
| Copper, Titanium | Trace |
Samarium–Cobalt Magnet Grades
| Alloy | Typical Composition |
|---|---|
| SmCo₅ | ~36% Sm, ~64% Co |
| Sm₂Co₁₇ | ~25% Sm, ~50–55% Co + Fe, Cu, Zr |
Key Magnetic Properties
| Property | Typical Range |
|---|---|
| Remanence (Br) | 0.8 – 1.3 T |
| Coercivity (Hc) | 50 – 2000 kA/m |
| Maximum Energy Product (BHmax) | 5 – 32 MGOe |
| Curie Temperature | 700 – 850 °C |
| Temperature Coefficient | Very low |
Mechanical Properties
| Property | Typical Range |
|---|---|
| Hardness | 450 – 700 HV |
| Elastic Modulus | 120 – 200 GPa |
| Tensile Strength | 300 – 900 MPa |
| Fracture Toughness | Low – Moderate |
| Wear Resistance | Good |
Strengthening & Metallurgical Behavior
• Precipitation hardening (Sm₂Co₁₇)
• Shape anisotropy (Alnico)
• Domain wall pinning
• Grain boundary engineering
• Controlled heat treatment and magnetic field alignment
Key Characteristics
✔ High magnetic strength
✔ Excellent thermal stability
✔ Low magnetic aging
✔ Strong resistance to demagnetization
✔ Stable under vibration and shock
Available Forms
Blocks
Rings
Discs
Segments
Rods
Custom magnet geometries
Bonded magnet composites
Applications
Aerospace & Defense
Aircraft sensors, guidance systems, actuators
Motors & Generators
High-speed motors, traction motors, wind turbines
Electronics
Microwave devices, sensors, audio equipment
Medical
MRI components, precision instruments
Advantages
✔ Superior high-temperature performance
✔ High magnetic energy density
✔ Excellent resistance to demagnetization
✔ Long service life
✔ Stable magnetic output
Limitations
❌ High material cost (especially SmCo)
❌ Brittle nature
❌ Limited machinability
❌ Dependence on cobalt supply
Why Choose Cobalt-Based Magnet Alloys?
Choose cobalt-based magnet alloys when operating temperatures exceed 200–300 °C, magnetic stability is critical, and long-term reliability outweighs cost concerns.