Aimants Alnico: High-Performance Magnet Explained

When people think of powerful magnets, néodyme (terre rare) vient souvent à l'esprit en premier. But long before neodymium dominated the market, there was Alnico—a magnet alloy that remains irreplaceable in high-temperature and precision applications. From electric guitar pickups to vintage sensors and aerospace components, Alnico magnets continue to play a vital role in modern engineering.

Dans ce guide complet, we will explore everything you need to know: what is an Alnico magnet, is Alnico a magnetic material, what are Alnico magnets made of, what is special about Alnico magnets, and finally—how to machine this hard, brittle alloy with minimal waste using boucle de fil de diamant Technique de coupe.

Alnico predates the rare-earth grades and is far more forgiving than comment couper les aimants en néodyme, but the same low-force principle applies.

What Is an Alnico Magnet?

An Alnico magnet is a type of permanent magnet made primarily from three key elements: Al (aluminium), Ni (nickel), and Co (cobalt). The name “Alnico” is a direct abbreviation of these three components. Developed in the 1930s, Alnico was the strongest permanent magnet available until the advent of rare-earth magnets in the 1970s.

Alnico magnets are known for their excellent temperature stability—they can operate at temperatures up to 550°C (1022°F) without significant loss of magnetic strength. They also exhibit high residual induction (Br) and good resistance to demagnetization, though their coercivity (resistance to being demagnetized) is lower than that of ceramic or neodymium magnets.

Today, Alnico magnets are produced in two common forms:

– Cast Alnico – Made by pouring molten alloy into sand or shell molds. Offers the highest magnetic output.

– Sintered Alnico – Made by pressing fine metal powder into a die and then heating. Provides tighter dimensional tolerances but slightly lower magnetic properties.

Is Alnico a Magnetic Material?

Oui, absolutely. Alnico is not only a magnetic material—it is one of the most important permanent magnetic materials in industrial history. To answer the question precisely: Alnico is a ferromagnetic material, meaning its atomic magnetic moments align spontaneously in the same direction, producing a strong external magnetic field.

Unlike soft magnetic materials (like iron or silicon steel), which lose their magnetism the moment an external field is removed, Alnico retains a significant portion of its magnetization. This makes it suitable for applications requiring a persistent, stable magnetic field without continuous power input.

Toutefois, Alnico has a unique characteristic: its coercivity is relatively low (typically 30–150 kA/m). This means that although it is a permanent magnet, it can be partially demagnetized if subjected to strong opposing magnetic fields. Designers often compensate by using longer, slender shapes that minimize the internal demagnetizing field.

What Are Alnico Magnets Made Of?

The composition of Alnico magnets varies by grade, but the standard formulation includes:

– Aluminum (Al) – 8–12%

– Nickel (Ni) – 15–26%

– Cobalt (Co) – 5–40%

– Fer (Fe) – Balance (typically 30–60%)

– Copper (Cu) – 3–4% (in some grades, to improve coercivity)

– Titanium (Ti) – 0–8% (added to increase coercivity further)

The most common commercial grades are Alnico 2 (low coercivity, high residual induction), Alnico 5 (the most widely used cast grade, with excellent magnetic output), and Alnico 8 (high coercivity, often containing titanium).

To produce an Alnico magnet, manufacturers melt these metals in an induction furnace, then cast or sinter them. After forming, the magnets undergo a specialized heat treatment in a magnetic field. During cooling, the magnetic field aligns the crystal structure, creating a preferred magnetization direction. This process, called “magnetic annealing,” is what gives Alnico its high residual induction.

What Is Special About Alnico Magnets?

Several properties make Alnico magnets unique and valuable despite the rise of neodymium and samarium-cobalt magnets.

1. Exceptional Temperature Stability

Alnico magnets maintain over 90% of their magnetic flux up to 500°C. À l’inverse,, neodymium magnets begin to irreversibly lose strength above 80–150°C. For applications like automotive sensors, aircraft instrumentation, and industrial tachometers exposed to high heat, Alnico remains the only viable choice.

2. High Residual Induction (Br)

Alnico magnets can achieve a residual flux density of up to 1.35 Tesla (for Alnico 5). This is comparable to many rare-earth magnets. Toutefois, because their coercivity is lower, they are typically used in closed magnetic circuits where the magnet is not exposed to strong opposing fields.

3. Excellent Corrosion Resistance

Unlike neodymium magnets, which require nickel or epoxy coating to prevent rust, Alnico contains no easily oxidized rare-earth elements. It resists atmospheric corrosion naturally, eliminating the need for protective coatings in most environments.

4. Stable Magnetism Over Time

Alnico magnets exhibit extremely low magnetic aging—less than 1% loss per decade. Once magnetized, they remain stable for decades, making them ideal for measurement devices, compasses, and reference magnets.

5. Unique Rechargeable Property

If an Alnico magnet is partially demagnetized, it can be fully restored to its original strength by placing it in a strong magnetizing fixture. This is not possible with ceramic or rare-earth magnets.

6. Distinctive Sound in Audio Applications

Musicians and audio engineers prize Alnico magnets for electric guitar pickups and moving-coil microphones. The slightly lower coercivity produces a softer, more “vintage” compression characteristic compared to ceramic magnets. Iconic guitar pickups like the PAF (Patent Applied For) humbucker used Alnico 2, 3, et 5.

Applications of Alnico Magnets

Because of these special properties, Aimants Alnico （Learn more professional knowledge）are found in:

– Electric guitar pickups – Vintage tone reproduction

– Automotive sensors – Speed and position sensors under the hood (high heat)

– Aerospace instruments – Magnetic compasses and tachometers

– Magnetos – Ignition systems for small aircraft and racing engines

– Microphones – Classic ribbon and dynamic designs

– Measuring instruments – Permanent magnet moving-coil (PMMC) mètres

– Magnetic separators – Low-intensity applications

How to Cut Alnico Magnets with Minimal Waste (Diamond Wire Loop Technology)

One challenge that manufacturers face with Alnico is post-casting machining. Alnico is both hard (45–50 HRC) and brittle, especially in cast form. Traditional cutting methods—abrasive saws, waterjet, ou GED (Usinage par électroérosion)—all have drawbacks:

– Abrasive wheels – Cause chipping, rough surface finish, and wide kerf (material loss)

– Waterjet – Can cause edge delamination and requires extensive cleanup

– EDM – Slow, expensive, and leaves a recast layer that may affect magnetic performance

The Solution: Découpe de boucle de fil diamanté

A diamond wire loop consists of a continuous stainless steel wire electroplated with industrial diamond grit. The loop rotates in one direction at high speed (typically4mm/min), grinding through hard materials like Alnico with precision and minimal waste.

Why diamond wire loop is ideal for Alnico magnets:

Conclusion

Alnico magnets are far from obsolete. Their exceptional temperature stability, high residual induction, résistance à la corrosion, and unique magnetic properties keep them relevant in demanding applications from guitar pickups to aerospace sensors. To answer the key questions: Alnico is absolutely a magnetic material, it is made from aluminum, nickel, cobalt, fer, and sometimes copper or titanium, and what is special about it is its ability to perform reliably at extreme temperatures and over decades of service.

Toutefois, cutting Alnico remains a manufacturing challenge due to its hardness and brittleness. Diamond wire loop technology solves this problem by delivering zero chipping, minimal kerf loss, no thermal damage, and a smooth surface finish. Whether you are producing custom-shaped Alnico 5 pickup magnets or high-coercivity Alnico 8 sensor components, un scie à boucle à fil diamanté is the optimal tool for precision and waste reduction.

Questions fréquemment posées

What are Alnico magnets made of?

Primarily aluminum (8-12%), nickel (15-26%), cobalt (5-40%) and iron (30-60%), with copper or titanium added in some grades to raise coercivity. Common commercial grades are Alnico 2, Alnico 5 and Alnico 8.

What is special about Alnico magnets?

Exceptional temperature stability (working up to 550 degC), high residual induction, natural corrosion resistance without coatings, extremely low magnetic aging, and the ability to be fully re-magnetized after partial demagnetization — a unique trait among permanent magnets.

Alnico vs neodymium magnets — which is better?

It depends on the application. Neodymium is far stronger at room temperature, but Alnico keeps its strength at temperatures where neodymium irreversibly fails (above 80-150 degC). For high-heat sensors, instruments and guitar pickups, Alnico is the better choice.

Can Alnico magnets be machined or cut?

Oui, but the alloy is hard and brittle, so abrasive saws chip it and EDM leaves a recast layer. Diamond wire loop cutting is the preferred method: zero edge chipping, a thin kerf that saves costly cobalt, no thermal damage, and a finish that often needs no secondary grinding.

Contenu technique examiné par l'équipe d'ingénierie d'Ensoll — un fabricant de boucles de fil diamanté avec 10+ des années d'expérience en production.