Glidcop is the registered trademark name of North American Höganäs, that refers to a family of copper-based metal matrix composite (MMC) alloys mixed primarily with aluminum oxide ceramic particles. The addition of small amounts of aluminum oxide has minuscule effects on the performance of the copper at room temperature (such as a small decrease in thermal and electrical conductivity), but greatly increases the copper's resistance to thermal softening and enhances high elevated temperature strength. The addition of aluminum oxide also increases resistance to radiation damage. As such, the alloy has found use in applications where high thermal conductivity or electrical conductivity is required while also maintaining strength at elevated temperatures or radiation levels.
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Composition and physical properties
Glidcop is available in several grades which have varying amounts of aluminum oxide content.
Additional materials and elements can be added if lower thermal expansion is required, or higher room temperature and elevated temperature strengths. The hardness can also be increased. A composite material of Glidcop AL-60 and 10 % Niobium provides high strength and high conductivity. The hardness is comparable to many copper-beryllium and copper-tungsten alloys, while the electrical conductivity is comparable to RWMA Class 2 alloy. Other additives for specialized applications include molybdenum, tungsten, Kovar, and Alloy 42.
At elevated temperatures, Glidcop maintains its strength much better than oxygen-free copper. The aluminum oxide particles in the copper block dislocation movement, which retards recrystallization and prevents grain growth. At 500 °C (932 °F) Glidcop AL-15 has a yield strength of over 29 ksi (200 MPa). Glidcop also has exceptional elevated temperature stress rupture strength when compared to oxygen-free copper.
Glidcop also has excellent resistance to softening after exposure to elevated temperatures.
Post-neutron-irradiation properties
Glidcop is resistant to degradation by neutron irradiation. For samples irradiated by neutrons at 411 °C (772 °F) and cooled to room temperature, the tensile strengths, swelling, and electrical conductivity were greater than that of pure copper. For samples irradiated from 0 to 150 dpm (displacements per atom), the tensile strength was nearly consistent, while the pure copper experienced a linear decrease in tensile strength on the range from 0 to 50 dpm. For sample swelling, the Glidcop had no noticeable swelling to 150 dpm while the pure copper had a linear growth to approximately 50 dpm, where swelling was 30 % of the original. For electrical conductivity, both the pure copper and Glidcop experienced linear drops in performance, though the Glidcop was less affected by the radiation.
Workability
Glidcop material is often acquired with a layer of cladding, typically 10-15 % of the cross-sectional area of the stock piece, though this varies depending on the production process. The cladding, which is a remnant of the extrusion process often used with Glidcop, must be machined (usually by milling or grinding) off the stock piece in order to take full advantage of the Glidcop properties. After the cladding is removed, machining and working with Glidcop is similar to that of pure copper.
Joining Glidcop material through brazing can be somewhat difficult. Brazing with silver based braze alloys can lead to problems due to the excessive diffusion of silver along grain boundaries. This is often circumvented by first electroplating the Glidcop part with either copper or nickel. The copper plating is often done in a copper cyanide solution since other solutions were found to be problematic. Brazing alloys used include 3565 AuCu and 5050 AuCu, which are used in a dry hydrogen atmosphere.
Glidcop also has excellent cold workability. Cold working by drawing, cold heading, or cold forming increase strength while reducing ductility.
Applications
Glidcop has been successfully applied to resistance welding electrodes to reduce stick to galvanized and other coated steels, and in incandescent light bulb leads by resisting softening after exposure to high temperatures. Likewise, Glidcop has found used in relay blades and contactor supports. The alloy's ability to maintain strength after high temperature brazing has led to use in hybrid circuit packages. Furthermore, it has found use in other high temperature applications such as x-ray tube components, and heat exchanger sections for fusion power and synchrotron units. Other uses include high field magnetic coils, sliding electrical contacts, arc welder electrodes, electronic leadframes, MIG contact tips, commutators, high speed motor and generator components, and microwave power tube components.
One of the more intensive uses of Glidcop has been in particle accelerator components, where the alloy may be subjected to high temperatures and high radiation simultaneously. Examples include Radio Frequency Quadrupoles (RFQs) and Compact Absorbers for High-Heat-Load X-ray Undulator Beamlines.