Beryllium-aluminium alloy

AlBeMet is the trade name of the Materion Brush Beryllium & Composites (formerly known as Brush Wellman) company for a beryllium and aluminium composite material derived by a powder metallurgy process. AlBeMet is formed by hot consolidating gas atomized prealloyed powder. Each powder particle contains aluminium between beryllium dendrites producing a uniform microstructure. Since beryllium is the second least dense elemental metal, these alloys are significantly less dense than aluminium.

Be-Al alloys are primarily of interest to the aerospace industry, due to the weight advantage they provide. They are currently used in satellites.

Due to the high toxicity of beryllium the machining has to be conducted with caution to prevent exposure of the workers.

Basic properties

AlBeMet® has a density of 2.071 g/cm³ (0.07482 lb/in³).

Mechanical properties

The mechanical properties of AM162 have been extensively characterized in all three-product forms. But a significant design database has been developed for the extruded product form. The extruded bar is fabricated by Cold Isostatic Pressing (CIPing) the isotropic spherical aluminum-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” x 25” (0.16 to 0.795 cm x 63.5 cm) length time’s 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 aluminum or steel, minimizes flexure and reduces the chance of mechanically induced failure.
• Thermal conductivity of approximately 210 W/m•K exceeds by about 25% that of common aluminum metal matrix composites such as Al 6061.
• The CTE of 13.9 ppm/K matches that of the ceramic chip carriers (alumina has CTE of ~8ppm/K) more closely than does aluminum, which has a CTE of 24ppm/K.
• The stiffness and low density of AlBeMet® are beneficial in aircraft, where high loads generated during tight maneuvering can cause flexure of circuit boards, and subsequent mechanical failure.

Fatigue properties

Is Cyclic fatigue critical to the life cycle of your component? 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, 1 x 10-7 cycles was about 207 MPa (30Ksi) in the longitudinal direction and 165 MPa (25 Ksi) in the transverse direction. This property is approximately 75% of the minimum RT yield strength, which is two times that of typical fatigue properties of 6061T6 aluminum.

Thermal Properties

Most important fact in Surface Mount Technology (SMT) circuit board cores is coefficient of thermal expansion (CTE).The better the CTE match, the less strain imposed on solder joints. Less strain translates into better fatigue life for solder joints and longer life for the board. Thermal management capabilities, characterized by the thermal conductivity and heat capacity, have also been found to be important factors.

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. However, it's highly carcinogenic properties mean that special precautions must be taken to avoid exposure, although the material is safe to handle when not being worked on.

See also

• Aluminium alloy