An amorphous alloy is a metallic alloy that lacks the long-range crystalline order found in conventional metals. These materials are also commonly called metallic glasses because they do not form a repeating crystal lattice.

Most amorphous alloys are multicomponent metallic systems designed to suppress crystallization during solidification. This guide explains the main alloy families, how metallic glass forms, how amorphous alloys are produced, and where they are used.

Crystalline and Amorphous Structure

Key Takeaways

Structure: Amorphous alloys lack long-range crystalline order, although local short-range atomic organization can still exist.
Types: Common alloy families include Fe-based, Co-based, Ni-based, Zr-based, Cu-based, and Ti-based systems.
Processing: Amorphous alloys are produced under conditions that suppress crystallization, commonly through rapid solidification for thin ribbons and specialized casting routes for bulk metallic glasses.
Uses: Applications include transformer cores, sensors, precision components, medical tools, and selected consumer products.
Limitations: Manufacturing cost, size constraints, and limited tensile ductility can remain challenges in some alloy systems.

What Is an Amorphous Alloy?

Unlike a conventional crystalline alloy, an amorphous alloy does not form a repeating crystal lattice during solidification. Local short-range atomic organization can still exist, but this arrangement does not repeat over long distances.

Is an Amorphous Alloy the Same as Metallic Glass?

In most materials-science contexts, amorphous alloy and metallic glass refer to the same general class of non-crystalline metallic materials. “Bulk metallic glass” is a more specific term for amorphous alloys that can retain their glassy structure in thicker sections.

Common Types of Amorphous Alloys

Amorphous alloys are often grouped by their dominant alloy system and intended application.

Fe-based amorphous alloys — widely used in transformer cores and other soft-magnetic components
Co-based amorphous alloys — used in selected magnetic and sensing applications
Ni-based amorphous alloys — used in specialized corrosion-resistant and magnetic systems
Zr-based bulk metallic glasses — common in structural and precision-component applications
Cu- and Ti-based bulk metallic glasses — used in selected high-strength engineering applications

Amorphous Alloy Structure at a Glance

Crystalline alloys contain long-range periodic atomic order and conventional crystal grains. Amorphous alloys lack this long-range order and conventional grain structure, although local short-range atomic organization can still remain.

At-a-Glance Comparison

The table below summarizes the main structural differences.

Feature	Crystalline Alloys	Amorphous Alloys (Metallic Glass)
Atomic Arrangement	Ordered, long-range lattice	No long-range periodic order; local short-range order remains
Grain Boundaries	Present, can be weak points	Absent
Solidification	Crystallization occurs during solidification	Crystallization is suppressed during solidification

How Are Amorphous Alloys Made?

The production process of amorphous alloys

The production process of amorphous alloys

Producing an amorphous alloy requires processing conditions that suppress crystallization during solidification. For thin amorphous ribbons, this commonly requires very rapid cooling, with cooling rates that can reach around 10⁵–10⁶ K/s. Bulk metallic glasses with higher glass-forming ability can retain an amorphous structure at much lower critical cooling rates.

Common Manufacturing Techniques

Several methods are used to achieve these high cooling rates:

Melt Spinning: A thin stream of melted metal is shot onto a very cold, fast-spinning copper wheel. This process quickly forms thin ribbons of amorphous metal.
Splat Quenching: A small volume of molten alloy is rapidly compressed between cooled surfaces, producing a thin section that solidifies quickly enough to suppress crystallization.
High-Pressure Die Casting: Molten alloy is injected into a cooled mold under pressure, allowing suitable bulk metallic glass compositions to solidify without extensive crystallization.

Key Characteristics of Amorphous Alloys

Depending on alloy composition and processing, amorphous alloys can exhibit several useful mechanical, corrosion, electrical, and magnetic characteristics.

High strength and elastic limits in many metallic glass systems
Good corrosion resistance in selected alloy families
Soft-magnetic behavior in some Fe- and Co-based amorphous alloys
Relatively high electrical resistivity in many soft-magnetic amorphous systems

For a detailed discussion of strength, ductility, corrosion resistance, electrical resistivity, and magnetic behavior, see our guide to amorphous metal properties.

Common Uses of Amorphous Alloys

Amorphous alloys are used in selected electrical, electronic, structural, medical, and consumer applications.

Electrical and Electronic Uses

One of the most established uses of Fe-based amorphous alloys is in transformer cores, where their soft-magnetic properties can reduce no-load loss compared with conventional silicon-steel designs. Amorphous alloys are also used in magnetic sensors and electronic security tags. For the underlying loss mechanism, see why amorphous core transformers have lower no-load loss.

High-efficiency transformers containing amorphous alloys

High-efficiency transformers containing amorphous alloys

Structural and Mechanical Uses

Bulk metallic glasses are used in selected precision, consumer, and sporting components where high strength, elastic recovery, dimensional stability, or surface durability are valuable.

Limitations of Amorphous Alloys

Manufacturing cost can be higher than for conventional alloys, particularly when specialized compositions or tightly controlled processing are required. Part size may also be limited by glass-forming ability and cooling requirements. In addition, some amorphous alloy systems show limited tensile ductility and can fail through localized shear bands.

Research continues to improve glass-forming ability, larger-part production, and additive manufacturing routes.

Common Questions

Is metallic glass actually glass?

No. “Metallic glass” refers to the material's non-crystalline atomic structure, not to conventional oxide glass. It remains metallic and retains properties such as electrical conductivity and metallic luster.

What is the main problem with amorphous alloys?

Common limitations include manufacturing cost, size constraints, and limited tensile ductility in some alloy systems. Their importance depends on alloy composition, part geometry, and processing route.

How strong is an amorphous alloy compared to steel?

Many amorphous alloys exhibit high strength and a high elastic limit, but direct comparison with steel depends on the specific amorphous alloy, steel grade, loading condition, and ductility requirement. A higher strength value alone does not make an amorphous alloy the better material for every application.

Are all amorphous alloys magnetic?

No. Magnetic behavior depends strongly on alloy composition. Many Fe- and Co-based amorphous alloys are developed as soft-magnetic materials, while Zr-, Ti-, and Cu-based bulk metallic glasses are generally selected for mechanical, corrosion, or processing characteristics rather than soft-magnetic performance.

What elements are commonly used in amorphous alloys?

Common amorphous alloy systems are based on iron, cobalt, nickel, zirconium, copper, or titanium combined with additional elements that help suppress crystallization and improve glass-forming ability. The exact composition depends on the required magnetic, mechanical, corrosion, and processing properties.

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