Beryllium-aluminum alloy an

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

that consists of 62%

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

and 38%

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, by weight, corresponding approximately to an empirical formula of Be₂Al. It was first developed in the 1960s by the Lockheed Missiles and Space Company, who called it Lockalloy, and used as a structural metal in the aerospace industry because of its high specific strength and stiffness. The material was used in the Lockheed YF12 aircraft and LGM-30 Minuteman missile systems. In the 1970s production difficulties limited the material to a few specialized uses and by the mid 1970s Lockalloy was no longer commercially available. In 1990, Materion Beryllium & Composites re-introduced the material into the commercial marketplace as a powder-sintered composite under the trade name of AlBeMet. AlBeMet is the

trade name A trade name, trading name, or business name is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is fictitious business name. Registering the fictitious name with ...

for a

and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

metal matrix

composite material A composite or composite material (also composition material) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a ...

derived by a powder metallurgy process. AlBeMet AM162 is manufactured by Materion Corporation Brush Beryllium and Composites (formerly known as Brush Wellman). AlBeMet is formed by hot consolidating gas atomized prealloyed powder. Each powder particle contains aluminium between beryllium dendrites producing a uniform microstructure. Aluminium-beryllium metal matrix composite combines the high modulus and low density characteristics of beryllium with the fabrication and mechanical property behaviors of aluminium. Due to weight advantage, Be-Al alloys are used in aerospace and satellite applications.

Basic properties

The composition of AlBeMet AM162 by relative weight is 38% Al, 62% Be. AlBeMet has a

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of 2.071 g/cm³ (0.07482 lb/in³).

Mechanical properties

The mechanical properties of AM162 have been characterized in all three-product forms with the extruded product form of AlBeMet having a significant design database. The extruded bar is fabricated by cold isostatic pressing (CIPing) the isotropic spherical aluminium-beryllium powder into semi-dense billets and then canning the billet for subsequent extrusion with a minimum of a 4:1 reduction ratio. Mechanical properties are minimum values at room temperature. Wrought mechanical properties for extrusions are in the longitudinal direction. Transverse properties are generally lower. A number of standard extrusion dies are available. Rolled product is available in a thickness range of 0.063” to 0.313” × 25” (0.16 to 0.795 cm × 63.5 cm) length times width dependent on gauge. Mechanical properties for HIP’d, extruded, and/or rolled AlBe metal matrix composites are in the annealed condition.

Physical properties

*High modulus-to-density ratio, 3.8 times that of aluminium or steel, minimizes flexure and reduces the chance of mechanically induced failure. *

Thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

of approximately 210 W/m⋅K exceeds by about 25% that of common aluminium matrix composites such as Al 6061. *Polished AlBeMet exhibits significant surface scatter inherent in the composite structure and cannot be eliminated by optical polishing. (Typical surface roughness from an AlBeMet polished surface is in the 200–250 Å finish.) An amorphous coating such as

electroless nickel plating Electroless Deposition, Electroless nickel-phosphorus plating, also referred to as ''E-nickel'', is a chemical engineering, chemical process that deposits an even layer of nickel-phosphorus alloy on the surface of a solid substrate, like metal o ...

is required. Surfaces in the 15 to 20 Å level are achievable. Depending on the coefficient of thermal expansion of the substrate material, a potential penalty of bi-metallic effect (bending forces?) between substrate and nickel surface finish is possible. With the tailoring of electroless nickel, this material dictates that the phosphorus content in the plating bath be approximately 11% to insure a CTE match close to that of the AlBeMet thereby eliminating any bi-metallic effect.

Fatigue properties

The fatigue properties of AlBeMet extruded material have been tested using the Krause rotating beam fatigue test utilizing fully reversed cycles with a R = +0.1. The

fatigue limit The fatigue limit or endurance limit is the stress (mechanics), stress level below which an infinite number of loading cycles can be applied to a material without causing fatigue (material), fatigue failure. Some metals such as ferrous alloys and ...

, 1 × 10⁷ cycles was about 207 MPa (30 ksi) in the longitudinal direction and 165 MPa (25 ksi) in the transverse direction. This property is approximately 75% of the minimum

yield strength In materials science and engineering, the yield point is the point on a stress–strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and w ...

at room temperature, which is two times that of typical fatigue properties of 6061-T6 aluminium.

Manufacture of AlBeMet components

AlBeMet parts can be manufactured with the same techniques normally used for aluminium, meaning that special tools do not need to be developed. Although the material is safe to handle when not being worked on, the

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...

of beryllium dust mean that special precautions must be taken to avoid exposure during machining with respiratory protection needed where dust could be formed.

References