alloy testing

Testing Information

Alloy testing is a materials analysis service offered by ZHONGXI Testing that determines the chemical composition, mechanical properties, microstructure, and surface characteristics of metallic alloys, and this service is provided for customers across aerospace, automotive, construction, marine, electronics, medical device, and general manufacturing fields. Alloys such as aluminum alloys, stainless steels, titanium alloys, copper alloys, nickel-based superalloys, and magnesium alloys are used wherever a combination of strength, corrosion resistance, heat resistance, machinability, or electrical conductivity is required, and each of these property sets depends directly on the precise balance of constituent elements and the processing history of the material.

The purpose of alloy testing is to verify that a material conforms to its designated grade specification, to identify unknown samples, to investigate failure or corrosion incidents, to support incoming material inspection, and to monitor quality during production. Techniques involved include spectrochemical analysis for elemental quantification, metallographic examination for grain size, phase distribution and inclusion rating, mechanical testing for tensile strength, yield strength, elongation and hardness, corrosion testing for resistance to specific environments, and non-destructive methods for internal defect detection. Together these techniques produce a data set that characterizes the alloy from bulk chemistry down to microstructural detail.

A typical testing process begins with sample registration and a review of the customer's stated grade, applicable specification, and intended test items. The laboratory then prepares specimens by sectioning, mounting, grinding, polishing, and etching as required for each method. Chemical analysis is performed on a polished or cleaned surface using spark-source optical emission spectrometry or X-ray fluorescence, with combustion and infrared methods applied for carbon, sulfur, oxygen, nitrogen, and hydrogen. Mechanical test pieces are machined to defined geometries and pulled on universal testing machines, while hardness is measured on prepared flats using Rockwell, Brinell, or Vickers scales. Metallographic replicas or mounted cross-sections are examined under optical and electron microscopy, and the collected data is compiled, checked against specification limits, and issued as a testing report.

Core parameters reported in alloy testing normally include the mass fraction of each alloying and residual element, tensile strength, yield strength, elongation after fracture, reduction of area, hardness values, impact energy, grain size number, non-metallic inclusion rating, and, where requested, corrosion rate or pitting assessment. The specific parameter list is selected according to the alloy family, the product form such as plate, sheet, bar, tube, forging or casting, and the specification the customer designates.

Testing Instruments

• Spark-source optical emission spectrometer — performs rapid quantitative multi-element analysis of metallic samples with a prepared flat surface.
• X-ray fluorescence spectrometer — non-destructive elemental analysis suited to sorting, screening, and samples that cannot be burned.
• Inductively coupled plasma atomic emission spectrometer — trace-level elemental determination after acid dissolution of the alloy sample.
• Carbon and sulfur analyzer — combustion-infrared instrumentation measuring carbon and sulfur in ferrous and non-ferrous alloys.
• Oxygen, nitrogen, and hydrogen analyzer — inert gas fusion analyzer quantifying dissolved and combined gases that affect embrittlement.
• Universal testing machine — applies controlled tensile, compression, and bend loading for strength and ductility measurement.
• Impact testing machine — pendulum Charpy and Izod tester for notch toughness determination at ambient and low temperature.
• Rockwell hardness tester — indentation hardness measurement with selectable scales for different alloy strengths and thicknesses.
• Brinell hardness tester — ball indentation testing for castings, forgings, and coarse structures.
• Vickers hardness tester — microhardness instrument with a diamond pyramid indenter for thin layers, coatings, and weld zones.
• Portable hardness tester — Leeb and ultrasonic contact impedance devices for on-site verification of large components.
• Metallographic microscope — upright and inverted optical systems with image analysis for grain size, inclusions, and phase rating.
• Scanning electron microscope with energy-dispersive spectroscopy — high-magnification fractography, phase identification, and micro-area composition.
• Metallographic specimen preparation equipment — sectioning saws, hot mounting presses, grinding and polishing machines for repeatable specimen preparation.
• Ultrasonic flaw detector — pulse-echo instrument for internal defect detection in plates, bars, forgings, and welds.
• Salt spray test chamber — accelerated corrosion exposure cabinet for neutral salt spray and modified solution testing.
• Muffle furnace and tube furnace — heat treatment and sensitization treatments required before certain corrosion and microstructure tests.
• Electronic analytical balance — sample weighing for dissolution-based chemical methods and density determination by Archimedes principle.
• X-ray diffraction instrument — phase identification, residual austenite quantification, and texture analysis in processed alloys.
• Electrolytic polishing and etching apparatus — preparation of strain-free surfaces for microstructure revelation and inclusion rating.

Testing Items

• Carbon content — the element that most strongly controls hardness and hardenability in ferrous alloys and must be held within tight limits for each grade.
• Silicon content — acts as a deoxidizer and strengthening element; deviation affects fluidity in castings and strength in wrought alloys.
• Manganese content — contributes to strength and hot workability and combines with sulfur to control sulfide inclusion morphology.
• Chromium content — determines corrosion resistance and passive film stability in stainless grades and hardenability in alloy steels.
• Nickel content — stabilizes austenite, improves toughness at low temperature, and is a base element of heat-resistant superalloys.
• Molybdenum content — enhances pitting corrosion resistance and high-temperature creep strength.
• Vanadium and titanium content — micro-alloying elements that provide grain refinement and precipitation strengthening.
• Copper and aluminum content — principal alloying elements in brasses, bronzes, and aluminum alloys, measured to confirm grade conformity.
• Sulfur and phosphorus content — residual elements whose excess causes hot shortness and embrittlement in steels.
• Trace and residual elements — lead, bismuth, antimony, arsenic, tin, and others controlled for machinability and embrittlement risk.
• Gas element analysis — oxygen, nitrogen, and hydrogen measured by inert gas fusion, since hydrogen embrittlement and nitride inclusions degrade ductility.
• Tensile strength — the maximum stress a specimen sustains and a primary acceptance criterion for structural alloys.
• Yield strength — the stress at the onset of plastic deformation, used for design allowable stress calculations.
• Elongation after fracture — a measure of ductility indicating the material's capacity for plastic deformation before failure.
• Reduction of area — a ductility indicator sensitive to inclusion content and internal soundness of forgings and castings.
• Rockwell hardness — rapid indentation measurement used for sorting, acceptance, and heat treatment verification.
• Brinell hardness — suited to coarse-grained and as-cast alloys where a larger indentation averages local structure.
• Vickers and microhardness — used for case depth measurement, coating hardness, and phase-specific hardness in welded zones.
• Impact toughness — Charpy V-notch energy absorption determining resistance to brittle fracture at service temperature.
• Grain size — a microstructural parameter influencing strength, toughness, and formability, reported as an ASTM grain size number.
• Non-metallic inclusion rating — assesses sulfide, oxide, and silicate cleanliness critical to fatigue life in bearing and spring steels.
• Microstructure examination — identifies phases, precipitates, decarburization, banding, and heat treatment condition.
• Macrostructure and low-magnification examination — reveals segregation, porosity, shrinkage cavities, and flow lines in castings and forgings.
• Intergranular corrosion test — evaluates susceptibility of stainless steels to grain boundary attack after sensitization.
• Pitting and crevice corrosion test — measures localized corrosion resistance of passive alloys in chloride environments.
• Salt spray corrosion test — accelerated exposure assessing protective coating and bare alloy corrosion behavior.
• Decarburization layer depth — quantifies carbon loss at the surface of heat-treated steel affecting fatigue performance.
• Case hardening depth — effective and total depth of carburized, carbonitrided, or nitrided layers measured microhardness traverse.
• Detect detection by ultrasonic examination — locates internal discontinuities such as voids, cracks, and laminations in billets and plates.
• Density measurement — verifies porosity level in powder metallurgy parts and castings against theoretical alloy density.

FAQ

How long does alloy testing take?

The standard turnaround is 7 to 15 working days depending on the number of test items and the sample type. Routine chemical composition analysis of a single metallic sample with a prepared surface is typically completed within 5 to 7 working days. Mechanical testing that requires machining of tensile specimens from plate, bar, or casting sections adds several days for specimen preparation. Corrosion tests such as neutral salt spray exposure run for a defined duration, for example 24, 48, 96, or 240 hours, plus evaluation time. Metallographic and hardness work generally completes within one week. If multiple techniques are combined in one project, the engineer confirms a delivery schedule at the time of quotation.

How much does alloy testing cost?

Cost is determined by the number of testing items selected, the analytical technique each item requires, and the sample preparation workload. A single-element confirmation or a quick spark optical emission composition scan is priced low, while a full package covering complete composition, tensile properties, hardness, impact toughness, metallography, and corrosion testing is quoted as a combination. Sample machining of tensile blanks, mounting and polishing for microscopy, and long-duration corrosion exposure each add preparation charges. Customers can send the alloy type, product form, and required test items to the laboratory engineers, who return a written quotation listing unit prices per item before testing begins.

Which test items are included in alloy testing?

The item list depends on the alloy family, the product form, and the applicable specification designated by the customer. For a typical steel sample, the package includes full chemical composition with carbon, sulfur, phosphorus, and alloying elements, tensile strength, yield strength, elongation, hardness, and metallographic grain size and inclusion rating. For an aluminum alloy, the emphasis shifts to silicon, magnesium, zinc, copper, and iron contents together with hardness and conductivity-related checks. For a stainless steel, intergranular corrosion susceptibility, pitting resistance, and ferrite content may be added. Customers may select a single item, a standard package for a designated grade, or a customized scheme; the engineers help map the items to the specification the material must satisfy.

How much sample should be prepared for alloy testing?

For chemical composition analysis alone, a sample of roughly 100 to 500 g is sufficient; a clean piece at least 20 mm by 20 mm with one flat surface works for spark optical emission and X-ray fluorescence. For tensile testing, the required stock depends on specimen geometry; a section of bar approximately 300 mm long, or a plate strip about 300 mm by 60 mm, allows standard proportional test pieces to be machined. For metallography, a coupon of about 20 mm by 20 mm by 15 mm is adequate. When a full package is ordered, sending 500 g to 1 kg of material in total generally covers all specimen preparation with margin. Samples should be labeled with the alloy grade and batch number and be free of oil, paint, and heavy oxidation on the analysis surface.

Testing Scope

• Aluminum alloy testing covering the 1xxx, 2xxx, 3xxx, 5xxx, 6xxx, and 7xxx series wrought alloys for structural, automotive, and aerospace applications.
• Casting aluminum alloy testing including Al-Si grades such as A356, ADC12, ZL104, and Al-Si-Cu systems used in die-cast housings and wheels.
• Stainless steel alloy testing covering austenitic grades 304, 316, 321, 347, duplex grades 2205 and 2507, and martensitic grades 410, 420, and 440.
• Carbon and low-alloy steel testing for grades such as Q235, Q345, Q355, 20#, 45#, 40Cr, 42CrMo, and 35CrMo structural steels.
• Spring steel and bearing steel alloy testing for 60Si2Mn, 65Mn, and GCr15 with attention to decarburization depth and inclusion cleanliness.
• Tool steel and die steel alloy testing including Cr12MoV, H13, D2, SKD61, and W18Cr4V high-speed steel.
• Titanium alloy testing for TA1, TA2 commercially pure grades and Ti-6Al-4V (TC4) aerospace and medical alloys.
• Copper alloy testing covering brass H59, H62, H65, H68, bronze QSn6.5-0.1, QAl9-4, and cupronickel B10, B30 grades.
• Nickel-based superalloy testing for Inconel 600, 625, 718, Incoloy 800H, Hastelloy C-276, and Monel 400.
• Magnesium alloy testing for AZ31, AZ61, AZ91, and ZK60 grades used in lightweight housings and castings.
• Zinc alloy testing for Zamak 3, Zamak 5, and ZA-8 die-casting alloys.
• Lead and tin alloy testing including solder alloys Sn63Pb37, lead-free SAC305, and bearing babbitt alloys.
• Cobalt-based alloy testing for Stellite wear-resistant grades and Co-Cr-Mo medical implant alloys.
• High-temperature boiler and pressure vessel steel alloy testing for 15CrMo, 12Cr1MoV, P22, P91, and P92 steels.
• Weathering steel alloy testing for Q355NH, 09CuPCrNi, and Corten-type grades with atmospheric corrosion resistance assessment.
• Rebar and wire rod alloy testing for HRB400, HRB500, and prestressing steel strand materials.
• Weld metal and welded joint alloy testing covering filler metals, dissimilar metal joints, and clad plate transition zones.
• Alloy powder testing for gas-atomized and water-atomized powders used in additive manufacturing and powder metallurgy.
• Alloy casting testing for gray iron, ductile iron QT400-18, QT500-7, vermicular iron, and high-chromium white iron.
• Alloy strip, foil, and wire testing for electronic connector materials, transformer silicon steel, and resistance alloys.
• Rare and precious alloy testing for gold, silver, platinum, and palladium jewelry and electrical contact alloys.
• Unknown alloy identification services for mixed, unlabeled, or legacy materials requiring full qualitative and quantitative characterization.

Summary

Alloy testing at ZHONGXI Testing covers chemical composition analysis, mechanical properties, hardness, metallographic structure, corrosion behavior, and defect examination for aluminum, steel, stainless, titanium, copper, nickel, magnesium, zinc, cobalt, and precious alloy materials in wrought, cast, powder, and welded forms. Turnaround is typically 7 to 15 working days depending on the selected items and sample type, and quotations are prepared by the laboratory engineers based on the requested test scheme.