Nickel Aluminum Bronze for Landing Gear Bushings

Nickel Aluminum Bronze Landing Gear Bushings

One of the most common uses of a Nickel Aluminum Bronze Alloy is as the base metal for landing gear bushings.  The high strength, ductility, and good abrasion resistance under severe loading conditions make Nickel Aluminum Bronze and ideal choice.  Both commercial and military aircrafts use Nickel Aluminum Bronze bushings for many of the pivot points contained in the landing gear.  These flanged bushings require a base metal able to withstand the most severe of conditions.  The most common Nickel Aluminum Bronze Alloys used for landing gear bushings are AMS 4640 C63000, AMS 4590 C63020, AMS 4880 C95510, and AMS 4881 C95520 Nickel Aluminum Bronze.

While bronze alloys have been in use for thousands of years, the addition of aluminum to the copper alloy is a relatively new accomplishment.  Dating back only to the early 1900’s aluminum is added to the alloy to give strength while maintaining high corrosion resistance.  While conventional aluminum bronze alloys are excellent for many demanding applications the demand for a stronger alloy became greater as the needs of critical applications became more and more demanding.

One of the most effective methods used to strengthen a copper alloys is the use of a thermal treatment.  Heat treatment of many of the copper alloys can improve the strength of the finished product.  Heat treatments rely on the ability of the atoms in the alloys crystals to diffuse through each other. Thermal treatments of copper alloys start with solution annealing. Think of this as similar to how you can dissolve more sugar in hot coffee than cold coffee.  As the super saturated hot coffee cools to room temperature the excess sugar will precipitate out of the coffee onto the bottom of the cup. During solution annealing the metal is heated to a temperature high enough to cause all of the alloying elements to diffuse evenly into the copper.  The amount of solute diffused into the copper when heated is greater than the solubility limit at room temperature.

Nickel Aluminum Bronze

Aluminum Bronze Alloys may be quenched hardened, quenching is the rapid cooling of the annealed material.  Since there is more alloying element diffused in the copper than the copper can hold at room temperature, the crystalline lattices of the grains are highly distorted.  The dislocations are essentially trapped with nowhere to go, producing an extremely hard and strong, but brittle material. This structure is often referred to as the martensitic structure.  Normally an alloy having a martensitic structure is further processed by annealing at a temperature of 1100° to 1250° F, which serves to increase the ductility of the alloy while decreasing the strength.

With conventional Aluminum Bronze Alloys, lower annealing temperatures cannot be used because the martensitic structure tends to transform to eutectoid.  This results in a more brittle alloy having reduced strength and loss of ductility. It was discovered that by adding nickel to the aluminum bronze alloy the tendency of the martensitic structure to transform to eutectoid is substantially suppressed or eliminated all togather. This suppression and/or elimination enables the alloy to be stress relieved and permits secondary alpha precipitation at temperatures in the range of 800° to 1050° F, which produces and alloy having high tensile strength, high yield strength, and good ductility.

The resulting Nickel Aluminum Bronze Alloy has ultra-high strength with the ability to be used in the most corrosive environments.


As stated above the most commonly used Nickel Aluminum Bronze Alloys for Landing Gear bushings are C63000, C63020, C95510, and C95520.  While these alloys all fall under the alloy family of Nickel Aluminum Bronze, there are difference that make them unique.  C63000 and C63020 are wrought alloys, meaning that they are an extruded product.  While C95510 and C95520 are cast alloys, generally manufactured via continuous casting.  C63020 and C95520 are also known as martensitic, which references the structure transformation that takes place. These 2 alloys are the strongest Nickel Aluminum Bronze Alloys.  In some cases they can be a substitute for Beryllium Copper due to their exceptional properties.

The wrought alloys (C63000 and C63020) are limited to solid shapes due to their manufacturing process.  This can increase the cost of landing gear bushings machined from the solid bar stock.  The solid shape increases both scrap loss and machine time.  The advantage of the cast alloys (C95510 and C95520) are in the fact that they can be cast in cored bar form.  With the closer net shape of the cored bar, there is less scrap loss and less machining time when manufacturing landing gear bushings.  The mechanical properties of the cast substitutes generally meet the wrought product standards.  This allows them to be used as an economical alternative to lower overall product costs.

Nickel Aluminum Bronze Landing Gear Bushings

Many Aerospace OEM’s have approved the cast products as acceptable material substitutes.  It is important to fully understand the various Nickel Aluminum Bronze Alloys and their individual specifications.  Follow the links below to learn more about Nickel Aluminum Bronze


C63000 AMS 4640 Nickel Aluminum Bronze

C95510 AMS 4880 Nickel Aluminum Bronze

C63020 AMS 4590 (Martensitic) Nickel Aluminum Bronze

C95520 AMS 4881 (Martensitic) Nickel Aluminum Bronze


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