Sm2co17 Magnets

These alloys (written as Sm₂Co₁₇, magnets, or SmCo Series 2:17 magnets) are age-hardened with a composition of two atoms of rare-earth samarium per 13–17 atoms of transition metals (TM). The TM content is rich in cobalt but contains other elements such as iron and copper. Other elements like zirconium, hafnium, and such may be added in small quantities to achieve better heat treatment response. By weight, the alloy will generally contain 25% of the samarium.

The maximum energy products of these alloys range from 20 to 32 MGOe, which is about 160-260 kJ/m³. These alloys have the best reversible temperature coefficient of all rare-earth alloys, typically being -0.03%/°C. The “second generation” materials can also be used at higher temperatures.

In Sm₂Co₁₇ magnets, the coercivity mechanism is based on domain wall pinning. Impurities inside the magnets impede the domain wall motion and thereby resist the magnetization reversal process. To increase the coercivity, impurities are intentionally added during the fabrication process.

SmCo is arguably the best permanent magnet material commercially available, with remanence similar to neodymium magnets, but with higher temperature ratings and with superior temperature stability. There are two types of SmCo magnets, SmCo 1:5 and SmCo 2:17.

SmCo magnet is a high-performance low-temperature coefficient permanent magnet made of samarium and cobalt and other rare earth elements. Sm-Co magnets can be operated at higher temperatures up to 300 C. Sm-Co materials come in energy products from 16 MGOe up to 33 MGOe. Their high resistance to demagnetizing influences and excellent thermal stability has ensured Sm-Co as the premium choice for the most demanding motor applications.

Advantage of Sm2co17 Magnets:

• Excellent thermal stability
• High magnetic properties
• Good corrosion resistance
• High resistance to demagnetization

Disadvantage Sm2co17 Magnets:

• Difficult to machine
• Expensive material (cobalt is market price sensitive)

The manufacturing process of Sm2co17 Magnets:

Both the types of SmCo magnets are manufacture by powder metallurgy. The raw materials are melted in a furnace and cast into thin sheets or ingot. The material is crushed and then pulverized by ball milling or by jet milling. The powder is then oriented with the external magnetic field and pressed into blocks or near-net shape. Final properties and density are achieved in following sintering and heat treatments. The blocks are then cut to shape and magnetized.