Evanohm Precision Resistance Nickel Alloy,Nickel Chromium Copper Aluminum Alloy,E FORU

### **Evanohm® Precision Resistance Alloy (Ni-Cr-Cu-Al Alloy)** #### **Overview** **Evanohm®** is a high-performance nickel-chromium-based precision resistance alloy, modified with additions of copper (Cu) and aluminum (Al). It is part of a specialized class of electrical resistance materials designed for applications requiring exceptional long-term stability, a very low and predictable Temperature Coefficient of Resistance (TCR), and high resistivity. Unlike standard Nichrome (Ni-Cr-Fe) alloys, the precise chemical balance of Evanohm results in a very stable microstructure. It forms a protective oxide layer that prevents further oxidation, allowing it to maintain its resistance value with minimal drift over time and under varying environmental conditions, even at elevated temperatures. This makes it the material of choice for high-precision resistors, sensors, and measuring instruments. --- #### **Chemical Composition (Weight % - Typical)** The composition is tightly controlled to achieve its unique electrical properties. | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | **Balance** (~75%) | | **Chromium (Cr)** | **19.0 - 21.0** | | **Copper (Cu)** | **2.0 - 4.0** | | **Aluminum (Al)** | **2.5 - 4.0** | | **Manganese (Mn)** | **0.10 - 0.30** | | **Silicon (Si)** | **0.20 - 0.50** | | **Iron (Fe)** | **≤ 0.50** | | **Carbon (C)** | **≤ 0.05** | * **Nickel (Ni):** Provides the base matrix and contributes to the alloy's ductility and corrosion resistance. * **Chromium (Cr):** The primary element for achieving high electrical resistivity and forming a stable, self-protecting oxide scale. * **Copper (Cu) and Aluminum (Al):** These are the critical modifying elements. They help in achieving a very **low Temperature Coefficient of Resistance (TCR)** by counterbalancing the inherent positive TCR of the Ni-Cr matrix. Aluminum also contributes to strengthening via precipitation hardening. * **Low Carbon & Iron:** Minimized to ensure microstructural stability and prevent detrimental phase formation that could degrade electrical properties. --- #### **Physical & Mechanical Properties** The following table outlines the key properties of Evanohm wire in the annealed and fully heat-treated condition. | Property | Value / Description | | :--- | :--- | | **Density** | 8.20 g/cm³ | | **Melting Point** | ~1380 °C (2515 °F) | | **Electrical Resistivity** | **133 μΩ·cm** (1.33 Ω·mm²/m) | | **Temperature Coefficient of Resistance (TCR)** | **±5 ppm/°C to ±20 ppm/°C** (Controllable through heat treatment, typically over 0-60°C range) | | **Thermal EMF vs. Copper** | < 1.5 μV/°C | | **Specific Heat** | ~450 J/kg·K | | **Tensile Strength (Annealed Wire)** | ~690 - 860 MPa (100 - 125 ksi) | | **Tensile Strength (Hard Drawn Wire)** | ~1240 - 1520 MPa (180 - 220 ksi) | | **Elongation (Annealed)** | 15% - 25% | | **Maximum Operating Temperature** | ~350 °C (660 °F) for long-term stability | --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Extremely Low Temperature Coefficient of Resistance (TCR):** Its most defining feature. The TCR can be engineered to be very close to zero through specific heat treatments, meaning its resistance changes very little with temperature fluctuations. 2. **High Electrical Resistivity:** Allows for the design of compact resistors with high resistance values using less material. 3. **Excellent Long-Term Stability:** Exhibits minimal resistance drift (aging effect) over time, even under continuous load, due to its stable metallurgical structure. 4. **Low Thermal EMF vs. Copper:** Minimizes parasitic thermoelectric voltages in precision circuits where connections to copper are made. 5. **Good Ductility and Weldability:** Can be drawn into fine wires and welded, facilitating the manufacturing of complex resistor grids and components. **Typical Applications:** Evanohm is used in applications where precision and stability are non-negotiable. * **Precision Resistors:** High-accuracy, low-TCR resistors used in military, aerospace, and medical equipment, as well as in laboratory-grade digital multimeters and calibration standards. * **Strain Gauges:** For high-precision stress analysis where signal drift must be minimized. * **Instrumentation & Sensors:** Components in bridge circuits, potentiometers, and sensitive transducers. * **Current Shunts:** For accurate current measurement with minimal temperature-induced error. * **High-Stability Heating Elements:** In specialized applications where consistent power output is critical. --- #### **International Standards** Evanohm is a proprietary alloy, and its specifications are often defined by its unique composition and performance requirements rather than a single generic international standard. | Standard / System | Designation / Type | Description | | :--- | :--- | :--- | | **ASTM** | **B267** | Specification for "Wire for Use in Wire-Wound Resistors." While this standard covers resistor wire generically, Evanohm's properties align with the highest stability classes defined within it. | | **MIL-SPEC** | **MIL-R-26** / **MIL-R-39009** | These military specifications for resistors (wirewound) often call out or are met by alloys with Evanohm's characteristics (low TCR, high stability). | | **IEC** | **IEC 60115** | International standard for fixed resistors for use in electronic equipment. High-stability wirewound resistors compliant with this standard often use alloys like Evanohm. | | **UNS** | **UNS NXXXXX** | Evanohm does not have a widely publicized UNS number, as it is a trademarked, proprietary product. It is typically specified by its trade name and guaranteed property sheet. | | **Trade Names** | **Evanohm®** (a trademark of the Wilbur B. Driver Company, now part of Aperam) | The most common industry name. Equivalent or similar alloys may be sold under other trade names (e.g., *Karma™* alloy is very similar and often used interchangeably). | --- #### **Summary** In summary, **Evanohm®** is a premier nickel-chromium-copper-aluminum alloy engineered specifically for the most demanding precision electrical resistance applications. Its ability to maintain a nearly constant resistance value across a wide temperature range and over time makes it an enabling material for advanced electronics, precision measurement, and control systems. While it is a proprietary material, its performance is recognized and specified in various industry and military standards for high-stability, low-TCR resistors.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3209 gallon liquid totes Special package is available on request.