CDA145 Tellurium Copper

Tellurium copper is a type of tellurium bronze material, with the ASTM standard grade C14500 in the United States. It is a high-conductivity, free-machining copper alloy developed by the United States in the 1960s in response to its industrial development needs, specifically to fill the gap in precision-machined copper alloy materials.

Tellurium copper combines good machinability with excellent electrical and thermal conductivity, as well as strong corrosion resistance and arc erosion resistance. It also offers good cold and hot workability, and can be processed through forging, casting, extrusion, drawing, and stamping. Products are available in various forms, including plates, sheets, rods, wires, tubes, and a range of custom-shaped profiles.

Tellurium copper refers to an alloy of tellurium and copper. With a tellurium content of 0.4–0.7%, the alloy exhibits excellent machinability. An alloy containing 50% tellurium and 50% copper is used as a master alloy.

The chemical composition (by mass percentage) of CDA145 (ASTM C14500) tellurium copper is as follows:

• Copper (Cu): ≥99.2% (balance) – ensures high electrical and thermal conductivity
• Tellurium (Te): 0.4% – 0.7% – forms a Cu₂Te brittle phase, significantly improving machinability without substantially reducing conductivity
• Phosphorus (P): 0.004% – 0.012% – acts primarily as a deoxidizer, refines the microstructure, and improves processing stability
• Impurities (e.g., Pb, Fe, Zn, etc.): Strictly controlled to ≤0.05% in total – maintains the high conductivity and corrosion resistance characteristic of high-purity copper alloys

This composition complies with the U.S. standard ASTM B301 (C14500) and corresponds to Chinese standard QTe0.5 and European standard CW118C (CuTeP). It is a typical high-conductivity, free-machining copper alloy.

CDA145 (corresponding to ASTM C14500 and national standard QTe0.5) is a high conductivity, easy to cut tellurium copper alloy with the following physical and mechanical properties

• Conductivity: 94-98% IACS (close to pure copper, better than most brass/bronze);
• Thermal conductivity: about 355 W/(m · K), higher than pure silver (429 W/(m · K)) but slightly lower than oxygen free copper in practical applications, still classified as a high thermal conductivity copper alloy;
• Mechanical properties (H04 state): Tensile strength ≥ 350 MPa, yield strength ≥ 330 MPa, elongation rate 8-12%, hardness ≥ 120 HV;
• Machinability: above 85% (based on 100% as the benchmark for easy cutting brass), with easy chip breakage and smooth surface, suitable for high-speed automatic turning;
• Density: about 8.94 g/cm ³, melting point 1051-1080 ° C, coefficient of thermal expansion (20-100 ° C) is about 16.5 × 10 ⁻⁶/K. ‌‌

Machinability

• The addition of 0.4%–0.7% tellurium in tellurium copper forms a brittle Cu₂Te phase with copper. This second phase is dispersed throughout the matrix, causing chips to undergo brittle fracture during machining and significantly reducing cutting resistance.
• In machinability tests using free-cutting brass (with a machinability rating of 100) as the reference, C14500 tellurium copper achieves a machinability rating of 85. During turning operations, surface roughness can reach as low as Ra 1.2 μm, and tool life is extended by up to three times compared to ordinary copper alloys.

Processing Advantages

• High-Speed Machining: Under high-speed cutting conditions (turning speed of 150–250 m/min, feed rate of 0.1–0.3 mm/r), tellurium copper maintains stable cutting performance, making it suitable for automated processing.
• Tool-Friendly: The formation of brittle chips reduces friction between the tool and the workpiece, minimizing tool wear. Diamond-coated carbide tools are recommended to further enhance machining efficiency.
• High Machining Accuracy: The cutting process generates less heat, resulting in minimal workpiece deformation. This makes tellurium copper ideal for machining precision components.

CDA145 tellurium copper alloy is mainly composed of copper and tellurium elements, with tellurium content ranging from 0.4% to 0.7%. This alloy material combines good machinability with excellent electrical and thermal conductivity, while also possessing resistance to corrosion and electrical erosion. Its cold and hot processing performance is good, and it can be forged, cast, extruded, drawn, punched and molded. It can be processed into various profiles and special-shaped materials such as plates, sheets, rods, wires, pipes, etc.

• Electrical Conductivity: ≥88% IACS (International Annealed Copper Standard) – higher than tin bronze (CuSn0.15, 85% IACS) and close to silver copper (CuAg0.1, 95% IACS). Suitable for high current density applications (e.g., contact current >5A/mm²).
• Mechanical Properties: Tensile strength ≥380 MPa, yield strength ≥280 MPa, elongation >25%. Combines strength with workability, supporting complex forming processes such as stamping and bending.
• Corrosion Resistance: Tellurium inhibits oxidation and sulfidation of copper. No corrosion observed after 1000 hours of neutral salt spray testing. Particularly resistant to sulfur-containing environments (e.g., chemical plant gases), outperforming ordinary brass.
• Wear Resistance: Low friction coefficient (<0.2). Wear volume after 10⁶ cycles is <0.15 mm³. Suitable for high-frequency plugging/unplugging or sliding contact components.
• Thermal Stability: Softening temperature >420°C. Electrical conductivity retention >80% at elevated temperatures (250°C), outperforming phosphor bronze (softening temperature <300°C).

Common delivery forms of CDA145 (C14500) tellurium copper include bars, plates, strips, tubes, and wire. Actual availability depends on the supplier's production capacity and the specific order requirements, and products are typically delivered as cut-to-length pieces or coils.

Delivery Conditions
Products are commonly supplied in the hot-extruded, cold-drawn, or annealed condition, with surfaces optionally polished or pickled.

Comments
Actual available forms and delivery conditions should be confirmed based on the technical agreement or standard (e.g., ASTM B187 / C14500) at the time of purchase. It is recommended to provide detailed drawings or specification requirements to obtain accurate information regarding the available product forms.

CDA145 (corresponding to ASTM C14500 and Chinese standard QTe0.5) is a high-conductivity, free-machining, arc-resistant, and corrosion-resistant copper alloy containing 0.4–0.7% tellurium. It is widely used in industrial fields requiring precision machining, high electrical conductivity, and resistance to arc erosion.

• Electronics & Electrical：Used in the manufacture of high-reliability connectors, switch contacts, high-current connectors for aerospace and new energy vehicles, and solar inverter components. The alloy combines high conductivity (≥85% IACS) with good anti-welding properties.
• Machined Components：Ideal for precision shafts, threaded parts, plumbing fittings, and motor components produced by high-speed automatic lathes. Compared to pure copper, it offers 1–2 times higher cutting efficiency and excellent chip breakability.
• Welding & Cutting：Used in plasma and oxy-acetylene cutting nozzles and electrode tips. These applications rely on the alloy's arc resistance, high-temperature durability (softening point ~300°C), and thermal conductivity.
• Specialized Equipment：Suitable for vacuum tube components, chemical valve and pump seals (resistant to mildly corrosive media), and medical devices (non-toxic and machinable). The alloy is also used in aerospace connectors and fasteners.
• Emerging Applications：Used in high-current terminals for charging stations, electrodes for semiconductor equipment, and battery electrical contacts. These applications benefit from the alloy's combined thermal conductivity, electrical conductivity, and machinability.

Q1:What is CDA145 Tellurium Copper?

A:CDA145 (ASTM C14500 / Chinese Standard QTe0.5) is a high-conductivity, free-machining copper alloy containing 0.4–0.7% tellurium. It is known for its excellent machinability, high electrical and thermal conductivity, good corrosion resistance, and arc erosion resistance.

Q2:What is the electrical conductivity of CDA145?

A:CDA145 offers electrical conductivity of ≥85% IACS (typically 94–98% IACS), which is close to pure copper and superior to most brasses and bronzes.

Q3:How machinable is CDA145?

A:CDA145 has a machinability rating of ≥85% (based on 100% for free-cutting brass). Compared to pure copper, it offers 1–2 times higher cutting efficiency, produces short, broken chips, and extends tool life by up to three times.

Q4: How does CDA145 perform in corrosion resistance?

A:CDA145 offers excellent resistance to atmospheric and freshwater corrosion. Tellurium inhibits oxidation and sulfidation, and the alloy shows no corrosion after 1000 hours of neutral salt spray testing. It is particularly resistant to sulfur-containing environments.

Q5:Is CDA145 suitable for welding?

A:Weldability is moderate. Heat input must be controlled to prevent tellurium segregation. Forging, extrusion, drawing, and stamping are all suitable processing methods.

Q6:What is the softening temperature?

A:CDA145 has a softening temperature of >420°C. At elevated temperatures (250°C), it retains >80% of its electrical conductivity, outperforming phosphor bronze (softening temperature <300°C).

Q7: Is CDA145 magnetic?

A:No. CDA145 is non-magnetic.

Q8:Can I get custom sizes and shapes?

A:Yes. Custom sizes and shapes are available upon request. It is recommended to provide detailed drawings or specification requirements to obtain accurate delivery options.

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