Nonferrous Metal Material Testing

Non-ferrous metal material inspection mainly conducts scientific testing and analysis on the chemical composition analysis, mechanical property testing, metallographic structure analysis, physical property testing, corrosion resistance testing and process property 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: The chemical composition of the non-ferrous metal material is the basis of its properties. Through the quantitative analysis of the contents of the alloying elements (such as the copper, aluminium, zinc, nickel, magnesium and titanium) and impurity elements (such as the iron, silicon, lead and cadmium), ensuring that they meet the standard provisions of the corresponding designations. It is the core link of the material acceptance and production process control.

Mechanical property testing: Mainly evaluates the behavior of the material under the applied forces, including the tensile strength, yield strength, elongation after fracture, reduction of area, hardness (Brinell, Rockwell and Vickers) and impact toughness, etc. These data are the direct basis of the structural design and safety evaluation, and directly affect the processing and use properties of the material.

Metallographic structure analysis: The micro-structures of the material are observed with the optical microscopes or electron microscopes, including the grain sizes, morphologies, phase compositions, distributions, inclusions, as well as the structure states after the heat treatment (such as the precipitated phases and textures), etc. The metallographic analysis is the key bridge connecting the material composition, processes and properties.

Physical property testing: Measures the parameters related to the physical characteristics of the material, such as the density, electrical conductivity, thermal conductivity, thermal expansion coefficient, melting point and specific heat capacity, etc. These properties are crucial for the application selection of the material in the specific fields such as the electrical engineering, electronics and heat exchange.

Corrosion resistance testing: Evaluates the ability of the non-ferrous metal material to resist the erosion of the environmental media. The common methods include the salt spray testing, intergranular corrosion testing, electrochemical testing (such as the polarization curves and electrochemical impedance spectroscopy) and atmospheric exposure testing, etc., to predict the durability of the material in the service environments.

Process property testing: Inspects the ability of the material to adapt to the subsequent processing and manufacturing, mainly including the bending testing, cupping testing (evaluating the formability), welding property testing, machinability testing, as well as the evaluation of the hot working properties such as the forging and extrusion, providing the guidance for the production process formulation.

Non-destructive testing: Under the premise of not damaging the use properties of the inspected objects, their surface or internal defects are detected. The common methods include the ultrasonic testing (UT, suitable for the internal defects), penetrant testing (PT, suitable for the surface open defects), eddy current testing (ET, suitable for the surface and near-surface defects of the conductive materials) and radiographic testing (RT).

Testing Scope

Light metals and their alloys: Mainly including the aluminium and aluminium alloys, magnesium and magnesium alloys, titanium and titanium alloys, etc. The testing emphases are the alloying states, heat treatment effects, specific strengths, corrosion resistance and high-temperature properties, widely applied in the aerospace, transportation and consumer electronics fields.

Heavy metals and their alloys: Covering the copper and copper alloys (such as the brass and bronze), nickel and nickel alloys, zinc and zinc alloys, lead and tin, etc. The testing focuses on the electrical and thermal conductivity, corrosion resistance, wear resistance, casting and processing properties. They are the key materials of the power, marine, chemical and precision instrument manufacturing.

Precious metal materials: Including the gold, silver, platinum, palladium and their alloys, etc. The testing requires the extremely high precision. In addition to the routine composition and mechanical properties, more attention is paid to the purity analysis, contact resistance, tarnish resistance and chemical stability in the specific media, used for the electronic contacts, ornaments and catalysts.

Rare metals and refractory metals: Such as the tungsten, molybdenum, tantalum, niobium, zirconium and hafnium and their alloys, etc. The testing emphases are their high melting points, high-temperature strengths, creep resistance, special nuclear properties (such as the neutron absorption cross-sections) and corrosion resistance in the extreme environments, applied in the nuclear energy, military industry and high-temperature furnaces.

Powder metallurgy materials: Made from the non-ferrous metal powders through the pressing and sintering. In addition to the properties of the material itself, the testing also includes the powder characteristics (particle sizes, morphologies and fluidity), product densities, porosities, sintering neck formation states, as well as the dimension precision and strengths of the final products.

Metal matrix composites: Made with the non-ferrous metals as the matrices and the ceramic particles, fibers and other reinforcement phases added. The testing needs to take into account the interface bonding states between the matrices and reinforcement phases, the distribution uniformity of the reinforcement phases, anisotropic properties, as well as the comprehensive property improvement effects of the composites.

Semi-finished products and finished products: The testing scope extends to the various castings, forgings, plates, strips, foils, pipes, bars, wires and final parts. The testing items need to be targeted selected and combined according to the product forms and use requirements.

Testing Methods

Spectroscopic analysis method: Used for the fast and accurate chemical composition analysis. Mainly including the inductively coupled plasma atomic emission spectrometry (ICP-OES) and spark direct-reading spectrometry (OES). The former is suitable for the solution samples with the low detection limits and wide element coverage; the latter is suitable for the solid samples and can directly carry out the fast in-situ analysis of the bulk materials.

Chemical titration method and gravimetric method: The classic and accurate chemical composition analysis methods. The titration method determines the contents through the quantitative reactions between the standard solutions and the tested components; the gravimetric method calculates through separating and weighing the masses of the tested components or their derivatives. Although time-consuming, they are often used as the arbitration methods and reference methods.

Tensile testing and compression testing: Carried out on the universal material testing machines. Through the recorded load-displacement curves, the strength and plasticity indicators of the material are obtained. The specimens need to be strictly prepared and the test rates, temperatures and other parameters need to be controlled according to the standards such as GB/T 228.1 or ASTM E8.

Hardness testing method: The different methods are selected according to the material hardness and states. The Brinell hardness (HBW) is suitable for the softer or coarse-grained materials; the Rockwell hardness (HRB, HRC, etc.) has the fast operation and is suitable for the finished product inspection; the Vickers hardness (HV) and micro hardness have the small indentations and can be used for the thin material or micro-area testing.

Metallographic specimen preparation and observation: Including a series of standardized processes such as the sampling, mounting, grinding, polishing and etching, and finally observing under the optical metallographic microscopes. For the finer structures, the scanning electron microscopes (SEM) combined with the energy dispersive spectrometers (EDS) need to be used for the morphology observation and micro-area composition analysis.

Electrochemical testing method: Used for the in-depth research of the corrosion mechanisms and rates. The potentiodynamic polarization curve method can evaluate the corrosion tendencies and rates of the material; the electrochemical impedance spectroscopy (EIS) can be used to study the coating properties, passivation film stability and the kinetic information of the corrosion processes.

Non-destructive testing technology: The ultrasonic testing utilizes the reflection/transmission characteristics of the high-frequency sound waves at the defects; the eddy current testing is based on the electromagnetic induction principle and is sensitive to the surface and near-surface defects of the conductive materials; the penetrant testing uses the capillary action to display the surface open defects; the radiographic testing images through the absorption differences of the different substances to the rays.

Testing Standards

Domestic Standards:

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

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

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

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

5. GB/T 231.1, Metallic materials — Brinell hardness test — Part 1: Test method

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

International Standards:

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

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

3. ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method

4. ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method

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

Direct-reading spectrometer: The main equipment of the fast chemical composition analysis of the non-ferrous metal materials. The instrument excites the samples to generate the characteristic spectra, which are received by the CCD detectors after the grating dispersion, and the element contents are obtained by comparing with the standard curves. It needs to be regularly calibrated with the standard samples to ensure the data accuracy.

Inductively coupled plasma mass spectrometer/optical emission spectrometer: The ICP-MS has the extremely low detection limits (up to the ppt level), used for the trace and ultra-trace element analysis; the ICP-OES has the detection limits at the ppb level, wide linear ranges and strong anti-interference abilities. Both need to prepare the samples into the solutions and are equipped with the auto sampling systems to improve the efficiency.

Universal material testing machine: The core equipment of carrying out the mechanical testing such as the tensile, compression, bending and shearing. The modern testing machines are composed of the precision loading frames, high-precision transducers, digital control systems and data analysis software, which can realize the various control modes such as the constant stress and constant strain, and automatically generate the test reports.

Hardness tester series: Including the Brinell, Rockwell, Vickers and micro hardness testers. The core of the equipment is the indenters, loading mechanisms and measurement systems. The micro hardness testers are usually integrated with the optical microscopes, used for the hardness testing on the tiny areas or specific phases, and are the important means of studying the micro mechanical properties of the material.

Metallographic microscope and scanning electron microscope: The metallographic microscopes are used for the low to medium magnification structure observation, equipped with the digital cameras for the image acquisition and analysis (such as the grain size ratings). The scanning electron microscopes (SEM) provide the higher resolutions and depths of field, and combined with the energy dispersive spectrometers (EDS), can carry out the qualitative and semi-quantitative analysis of the micro-area compositions.

Electrochemical workstation: Integrating the potentiostats, galvanostats and frequency response analysers, through the three-electrode systems (working electrodes, reference electrodes and counter electrodes), it precisely controls and measures the electrode potentials and currents, used to complete the various electrochemical testing such as the polarization curves and impedance spectra. It is the key equipment of the corrosion research and evaluation.

Non-destructive testing equipment: Including the ultrasonic flaw detectors (with the probes of the different frequencies and angles), eddy current flaw detectors (with the various detection coils), penetrant testing kits (cleaners, penetrants and developers) and X-ray or γ-ray real-time imaging systems. These equipment need to be operated by the certified professionals and regularly carry out the performance verifications.