Beryllium Copper Testing

Beryllium copper inspection mainly conducts scientific testing and analysis on the chemical composition analysis, mechanical property testing, physical property testing, metallographic structure analysis, corrosion resistance testing and process performance testing, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Chemical composition analysis: This is the basic item of the beryllium copper inspection, aiming to precisely determine the contents of the beryllium (Be), copper (Cu) and other alloying elements (such as the nickel, cobalt, iron and silicon) in the material. The composition analysis is the key basis for judging the material designation conformity (such as C17200 and C17500) and predicting its performance. The beryllium content is usually required to be controlled within 1.6%-2.0%, to ensure its elasticity and strength.

Mechanical property testing: Mainly used to evaluate the behaviour of the beryllium copper under the loading conditions. The core tests include the tensile testing (determining the tensile strength, yield strength and elongation), hardness testing (commonly the Rockwell hardness HRB or HRC) and the elastic modulus determination. These data are directly related to the reliability and service life of the material as the key components such as the springs, diaphragms and connectors.

Physical property testing: Including the determination of the parameters such as the density, thermal conductivity, electrical conductivity and thermal expansion coefficient of the beryllium copper. These properties determine the applicability of the material in the electronic and electrical fields. For example, the high electrical conductivity is the prerequisite for the beryllium copper used to manufacture the high-reliability electrical contact elements, usually measured in %IACS (International Annealed Copper Standard).

Metallographic structure analysis: The microstructure of the material is observed through an optical microscope or scanning electron microscope (SEM), evaluating the grain size, second-phase distribution and whether there are the inclusions or defects. For the beryllium copper after the solution treatment and aging, the morphology and distribution of the precipitation strengthening phase (γ phase) are the important indicators determining its peak performance.

Corrosion resistance testing: Evaluates the corrosion resistance of the beryllium copper in the different environmental media (such as the salt spray, acidic and alkaline environments). The common testing methods include the neutral salt spray testing (NSS), acetic acid accelerated salt spray testing (AASS) and electrochemical testing. The good corrosion resistance ensures its stability and durability under the harsh working conditions.

Process performance testing: The testing is carried out according to the processing and application characteristics of the beryllium copper, mainly including the bending testing, cupping testing (evaluating the formability) and brazing and welding performance testing. These tests ensure that the material will not crack or deteriorate in performance during the subsequent manufacturing processes (such as the stamping, bending and joining).

Testing Scope

Incoming inspection of the raw materials: The comprehensive incoming testing of the procured raw materials such as the beryllium copper bars, wires, strips and sheets is carried out, ensuring that their chemical composition, mechanical properties and physical properties meet the requirements of the procurement technical agreements or the relevant standards (such as ASTM B196 and GB/T 5233), controlling the product quality from the source.

Production process monitoring: The sampling testing is carried out in the key processes such as the heat treatment (solution and aging), cold working (drawing and rolling) and forming of the beryllium copper parts. The hardness, strength and metallographic structure changes after the heat treatment are emphatically monitored, ensuring the stability of the process parameters and the product performance reaching the design expectations.

Performance verification of the finished parts: The final performance confirmation is carried out on the manufactured beryllium copper parts (such as the electronic connectors, spring contacts, instrument bellows and explosion-proof tools). The testing items are determined according to their service conditions, and may include the mechanical properties, electrical properties, fatigue resistance and dimensional precision.

Failure analysis and difficult diagnosis: When the early failures (such as the fracture, stress relaxation, poor contact and abnormal corrosion) of the beryllium copper parts occur during the use, the root causes of the failure are traced through the systematic testing means (fracture analysis, composition analysis and structure observation), providing the technical basis for improving the design, material or process.

Designation identification and material arbitration: In the scenarios such as the material mixing, quality disputes or used equipment evaluation, the designation identification of the unknown beryllium copper materials is carried out through the professional testing means, confirming whether they are consistent with the declared designations, or serving as the basis for the third-party arbitration.

Research and development support: During the development of the new materials, research of the new processes or expansion of the application fields, the systematic testing data are used to evaluate the performance change laws of the beryllium copper materials under the different compositions and processes, guiding the research and development direction and optimizing the material systems.

Testing Methods

Inductively coupled plasma optical emission spectrometry method (ICP-OES): The mainstream method currently used for the quantitative analysis of the chemical composition of the beryllium copper. Its principle is to use the plasma to excite the atoms in the sample, and determine the element contents by measuring the intensities of the characteristic spectral lines. This method has the advantages of the low detection limits, high precision and simultaneous multi-element analysis, and is particularly suitable for the precise determination of the key elements such as the beryllium and nickel.

Spark direct-reading optical emission spectrometry (OES): A fast and efficient on-site or laboratory composition analysis method. The characteristic spectra of the various elements are directly measured through the spark discharge excitation of the sample surface. It is suitable for the fast sorting and process control at the production sites, but has the high requirements for the sample surface preparation, and the sensitivity to the light elements such as the beryllium is slightly inferior to the ICP.

Tensile testing on a universal material testing machine: In accordance with the standards such as ASTM E8/E8M or GB/T 228.1, the standard specimens are stretched at a constant rate on the testing machine until the fracture, thereby obtaining the key mechanical property parameters such as the tensile strength, yield strength and elongation after fracture of the material. It is the basic method for evaluating the load-bearing capacity of the material.

Hardness testing (Rockwell/Vickers/Brinell): The indenter is pressed into the material surface under the specific load, and the indentation size or depth is measured to characterize the hardness of the material. The Rockwell hardness (HRB/HRC) testing is fast and simple, commonly used for the production inspection; the Vickers hardness (HV) testing has the high precision, suitable for the thin materials or micro areas; the Brinell hardness (HBW) is used for the softer or coarse-grained materials.

Metallographic microscopic analysis method: The metallographic specimens are prepared through the cutting, mounting, grinding, polishing and chemical etching, and the microstructure is observed under an optical microscope. It is used to evaluate the grain size (according to ASTM E112), second-phase distribution, inclusion levels and heat treatment effects, and is the bridge connecting the process and performance.

Scanning electron microscope and energy dispersive spectroscopy (SEM/EDS): The SEM provides the high-resolution micro-morphology images, used to observe the fracture characteristics and precipitate morphologies; the EDS can carry out the qualitative and semi-quantitative analysis of the micro-area elements. The combination of the two is a powerful tool for the failure analysis and in-depth material research.

Testing Standards

Domestic Standards:

1. GB/T 5233, Beryllium bronze sheets and strips

2. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

3. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

4. GB/T 232-2010, Metallic materials — Bend test method

5. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

6. GB/T 4340.1-2009, Metallic materials — Vickers hardness test — Part 1: Test method

International Standards:

1. ASTM B196, Standard specification for copper-beryllium alloy rod and bar

2. ASTM E8/E8M, Standard test methods for tension testing of metallic materials

3. ASTM E112, Standard test methods for determining average grain size

4. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

5. ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Inductively coupled plasma optical emission spectrometer (ICP-OES): The core equipment of the chemical analysis, composed of a sample introduction system, plasma light source, spectroscopic system and detection system. The high-precision models can detect the element contents at the ppm or even ppb levels, and are equipped with the autosamplers to improve the detection efficiency and consistency. It is the essential instrument for ensuring the precise control of the beryllium copper composition.

Direct-reading optical emission spectrometer: Usually of the bench-type or mobile design, including the excitation stand, optical system, detector and data processing unit. Its advantage is that the composition results of the main elements can be obtained within a few seconds, which is very suitable for the occasions requiring the fast decisions such as the foundry workshops and incoming material warehouses, but has the strong dependence on the standard samples.

Universal material testing machine: The electronic universal testing machine equipped with the high-precision sensors, servo control system and data acquisition software is the standard equipment for carrying out the mechanical tests such as the tensile, compression and bending. During the testing, the standard-compliant tensile fixtures and extensometers need to be used, to ensure the accuracy of the strain measurement.

Hardness tester: Including the Rockwell hardness testers, Vickers hardness testers and micro-hardness testers. The modern hardness testers usually have the functions of the automatic loading, digital display and data processing. The micro-hardness tester (such as the Vickers) is particularly suitable for testing the hardness of the beryllium copper thin strips, coatings or specific phase areas because of its small indentations.

Metallographic microscope and sample preparation equipment: The metallographic microscope is the basis of the structure observation, equipped with the observation modes such as the bright field, dark field and polarization. The complete sample preparation process requires the cutting machines, mounting machines, pre-grinding machines, polishing machines, as well as the electrolytic polishing or chemical etching devices, to prepare the qualified specimens free of the scratches and deformations.

Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS): The SEM provides the surface morphology information at the nanometre-level resolution, and the EDS can realize the micro-area element composition analysis. For the beryllium copper, the shape, size and distribution of the aging precipitates can be detected and observed under the SEM, and combined with the EDS, the composition of the precipitates can be analysed. They are the key equipment for the in-depth research of the material strengthening mechanism and failure causes.