# UNS C17200 copper alloy

Select copper-beryllium by product form, temper, aging route and conductivity, with process-specific beryllium exposure controls.

Reviewed: 2026-11-01

Tags: materials, copper-alloys, heat-treatment, electrical-contacts

## Identify the alloy and supplied condition

NGK's **Berylco Alloy 25 rod, bar and tube** data list **140 MPa minimum 0.2% yield and 17% IACS minimum** for **A/TB00**, versus **1,000 MPa and 22% IACS** for **aged AT/TF00**. These are supplier reference minima. Verify the purchase requirements for the ordered form and size. NGK gives **3 hours at 600°F** as a typical AT aging entry. Use separate strip data for formed contact springs. [NGK rod, bar and tube properties](https://www.ngkmetals.com/technical/properties/rod-bar-tube-berylco-alloy-25-uns-17200-properties/)

**UNS C17200** is a high-strength, precipitation-hardenable copper-beryllium alloy. NGK identifies it as **CuBe2 / CW101C / Berylco 25**, supplying strip, rod, wire and plate among other forms. These commercial and cross-system designations help identify candidate stock; they do not replace the ordered product standard, temper and inspection requirements. [NGK C17200 product reference](https://www.ngk-alloys.com/product/our-alloys/c17200/)

Materion's Alloy 25 strip sheet gives **1.80–2.00 wt.% beryllium**, nickel plus cobalt **≥0.2%**, nickel plus cobalt plus iron **≤0.6%**, and copper balance. The same sheet lists ASTM B194 among its strip specifications. Retain manufacturer/product identity and the applicable standard/revision rather than purchasing only “beryllium copper.” [Materion Alloy 25 strip, DS-AS-24](https://hkvxni.files.cmp.optimizely.com/download/b97f9c2aa04211eeb43acac3311fc08f)

## Distinguish age-hardenable, aged and mill-hardened tempers

NGK's temper terminology separates these routes:

| Condition | Example designation | Meaning for processing |
| --- | --- | --- |
| Annealed, age-hardenable | A / TB00 | Form or machine, then apply the specified aging treatment if final hardened properties are required |
| Cold-worked, age-hardenable | H / TD04 | Cold-worked stock awaiting its selected aging route |
| Annealed and heat treated | AT / TF00 | Heat-treated counterpart of the annealed condition |
| Hard and heat treated | HT / TH04 | Heat-treated counterpart of the hard condition |
| Mill hardened | Examples include TM00 and TM04 | Controlled mill processing supplies a selected strength/formability combination |

Mill-hardened products are normally formed and used at their supplied strength, but NGK also describes applications involving subsequent full heat treatment. Specify the actual product route; “mill hardened” does not authorize an arbitrary additional aging cycle. [NGK temper terminology](https://www.ngkmetals.com/technical/temper-terminology/)

## Read mechanical properties by form and temper

NGK's **Berylco Alloy 25 rod/bar/tube** reference lists:

| Property | A / TB00 | AT / TF00 | HT / TH04 |
| --- | --- | --- | --- |
| Tensile strength | 410–590 MPa | 1140–1380 MPa | 1240–1520 MPa |
| 0.2% yield strength, minimum | 140 MPa | 1000 MPa | 1070 MPa |
| Elongation in 4D, minimum | 20% | 4% | 2% |
| Electrical conductivity, minimum | 17% IACS | 22% IACS | 22% IACS |

These are that supplier's form-specific reference entries. Confirm applicability to the ordered dimensions and acceptance specification. Their typical aging entries distinguish AT at **3 hours / 600°F** from HT at **2 hours / 600°F**. A heat-treatment reference is not evidence that an uncontrolled furnace cycle produced those properties. [NGK rod, bar and tube properties](https://www.ngkmetals.com/technical/properties/rod-bar-tube-berylco-alloy-25-uns-17200-properties/)

Forming limits also need their footnotes. Materion's strip bend ratios apply only to **0.010 in (0.25 mm) and thinner**; its elongation figures apply only above **0.004 in (0.10 mm)**. Preserve bend direction and thickness when selecting stock. Thin-strip data do not establish thick-plate bend capability. [Materion strip sheet](https://hkvxni.files.cmp.optimizely.com/download/b97f9c2aa04211eeb43acac3311fc08f)

## Aging, distortion and surface processing

Materion explains that age hardening precipitates a hard beryllide phase and can change dimensions. For high-strength alloys including Alloy 25, it describes approximately **0.6% volume contraction**, corresponding to about **0.2% linear contraction**. Cold-work residual stresses and part geometry can additionally affect shape. [Materion distortion guidance, January 1, 2024](https://www.materion.com/ja/insights/material-matters-blog/in-our-element-how-can-shape-distortion-of-high-strength-copper-beryllium-be-controlled)

**Illustrative allowance:** applying a nominal 0.2% linear contraction to a 50.00 mm feature gives 50.00 × 0.002 = **0.10 mm**, or approximately 49.90 mm after contraction. This is arithmetic using the supplier's approximate behavior, not a machining compensation rule. Verify the actual stock, orientation, machining sequence, fixtures and qualified cycle before assigning a finished tolerance.

Record the incoming temper, qualified time at part temperature, furnace control, loading and final tests. Confirm whether machining/forming precedes aging or whether pre-hardened stock is intended. Do not infer a solution-annealing process from an age-hardening entry; those are separate processing steps.

Heat treatment also affects subsequent joining and coating. Materion describes mixed beryllium/copper oxide films whose composition and thickness depend on atmosphere and temperature. It notes that hydrogen does not reduce beryllium oxide. Establish cleaning and surface preparation for the actual plating, soldering or bonding operation rather than assuming an inert or reducing atmosphere leaves a ready-to-join surface. [Materion cleaning guidance, March 13, 2024](https://www.materion.com/de/insights/material-matters-blog/in-our-element-how-do-you-clean-copper-beryllium)

## Conductivity and component selection

Materion reports **22–28% IACS** as typical for Alloy 25 strip in the precipitation-age-hardened condition. This is neither its annealed conductivity nor the value for every C17200 product. Its sheet explicitly treats properties as selection references rather than a material specification. [Materion strip data](https://hkvxni.files.cmp.optimizely.com/download/b97f9c2aa04211eeb43acac3311fc08f)

Select a contact or spring against its combined requirements: elastic deflection, force, permanent set, fatigue, stress relaxation, current, contact resistance and temperature. A tensile-strength entry does not establish spring life, and bulk conductivity does not establish a plated connection's resistance. Retain service temperature and exposure duration with any relaxation or aging assessment; do not turn an aging temperature into a continuous service rating.

NGK's machining guidance distinguishes annealed, hard and AT/HT stock, and says its rod/bar/tube cutting recommendations assume carbide tools. It also identifies machine rigidity, coolant and tool geometry as influences. Use the relevant starting guidance and qualify finish, dimensions and burr removal on actual stock rather than applying one universal speed/feed table. [NGK machining guidelines](https://www.ngkmetals.com/technical/machining-guidelines/)

## Beryllium processing controls

NGK's currently linked **US Copper Beryllium Wrought Alloys SDS, version 1.1, revised September 1, 2023**, explicitly covers Alloy 25/C17200. It distinguishes solid stock from operations producing particulate, including grinding, milling, welding, heat treatment and chemical cleaning. It identifies serious inhalation hazards, including chronic beryllium disease and cancer. An intact component's handling conditions do not describe machining dust or fume. [NGK US wrought-alloy SDS](https://www.ngkmetals.com/wp-content/uploads/Wrought-United-States.pdf)

The SDS calls for suitable enclosure/local exhaust or other engineering controls, containment of dust-handling systems, protective equipment selected for the exposure, HEPA vacuum cleanup and avoidance of compressed-air dispersal. Arrange process-specific exposure assessment, housekeeping and waste handling before fabrication, including outsourced finishing. Obtain the current regional SDS for the actual supplier's product. [NGK SDS, sections 6–8](https://www.ngkmetals.com/wp-content/uploads/Wrought-United-States.pdf)

## Source versions and release

Primary sources were reviewed November 1, 2026. The Materion strip PDF prints **DS-AS-24 / ©2021**; its copyright is not a claimed 2026 revision. NGK's product/property pages have no visible technical revision date. The SDS dates above come from its header, not its hosting path.

Release against the agreed grade, form, final temper, dimensional/surface requirements and required test results. Retain heat-treatment and finishing identity with the lot. Application lists and material-family descriptions establish candidates, while the finished component still needs evidence for its actual loading and environment.

[Grades, conditions and material selection](../grades-tempers-and-conditions.md)