ASTM B954-23

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Designation: B954 − 15 B954 − 23
Standard Test Method for
Analysis of Magnesium and Magnesium Alloys by Atomic
Emission Spectrometry
This standard is issued under the fixed designation B954; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method describes the analysis of magnesium and its alloys by atomic emission spectrometry. The magnesium
specimen to be analyzed may be in the form of a chill cast disk, casting, sheet, plate, extrusion or some other wrought form or
shape. The elements covered in the scope of this method are listed in the table below.
Element Mass Fraction Range (Wt %)
Aluminum 0.001 to 12.0
Beryllium 0.0001 to 0.01
Boron 0.0001 to 0.01
Cadmium 0.0001 to 0.05
Calcium 0.0005 to 0.05
Cerium 0.01 to 3.0
Chromium 0.0002 to 0.005
Copper 0.001 to 0.05
Dysprosium 0.01 to 1.0
Erbium 0.01 to 1.0
Gadolinium 0.01 to 3.0
Iron 0.001 to 0.06
Lanthanum 0.01 to 1.5
Lead 0.005 to 0.1
Lithium 0.001 to 0.05
Manganese 0.001 to 2.0
Neodymium 0.01 to 3.0
Nickel 0.0005 to 0.05
Phosphorus 0.0002 to 0.01
Praseodymium 0.01 to 0.5
Samarium 0.01 to 1.0
Silicon 0.002 to 5.0
Silver 0.001 to 0.2
Sodium 0.0005 to 0.01
Strontium 0.01 to 4.0
Tin 0.002 to 0.05
Titanium 0.001 to 0.02
Yttrium 0.02 to 7.0
Ytterbium 0.01 to 1.0
Zinc 0.001 to 10.0
Zirconium 0.001 to 1.0
NOTE 1—The mass fraction ranges given in the above scope are estimates based on two manufacturers observations and data provided by a supplier of
atomic emission spectrometers. The range shown for each element does not demonstrate the actual usable analytical range for that element. The usable
analytical range may be extended higher or lower based on individual instrument capability, spectral characteristics of the specific element wavelength
This test method is under the jurisdiction of ASTM Committee B07 on Light Metals and Alloys and is the direct responsibility of Subcommittee B07.04 on Magnesium
Alloy Cast and Wrought Products.
Current edition approved Oct. 1, 2015April 1, 2023. Published November 2015April 2023. Originally approved in 2007. Last previous edition approved in 20072015 as
B954 – 07.B954 – 15. DOI: 10.1520/B0954-15.10.1520/B0954-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B954 − 23
being used and the availability of appropriate reference materials.
1.2 This test method is suitable primarily for the analysis of chill cast disks as described in Sampling Practice B953. Other forms
may be analyzed, provided that: (1) they are sufficiently massive to prevent undue heating, (2) they allow machining to provide
a clean, flat surface which creates a seal between the specimen and the spark stand, and (3) reference materials of a similar
metallurgical condition (spectrochemical response) and chemical composition are available.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use. Specific safety and health statements are given in Section 10.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
B953 Practice for Sampling Magnesium and Magnesium Alloys for Spectrochemical Analysis
E135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
E305 Practice for Establishing and Controlling Spark Atomic Emission Spectrochemical Analytical Curves
E406 Practice for Using Controlled Atmospheres in Atomic Emission Spectrometry
E826 Practice for Testing Homogeneity of a Metal Lot or Batch in Solid Form by Spark Atomic Emission Spectrometry
(Withdrawn 2023)
E1257 Guide for Evaluating Grinding Materials Used for Surface Preparation in Spectrochemical Analysis
E1329 Practice for Verification and Use of Control Charts in Spectrochemical Analysis (Withdrawn 2019)
E1507 Guide for Describing and Specifying the Spectrometer of an Optical Emission Direct-Reading Instrument
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology E135.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 binary type calibration—calibration curves determined using binary calibrants (primary magnesium to which has been added
one specific element).
3.2.2 global type calibration—calibration curves determined using calibrants from many different alloys with considerable
compositional differences.
3.2.3 alloy type calibration—calibration curves determined using calibrants from alloys with similar compositions.
3.2.4 two point drift correction—the practice of analyzing a high and low standardant for each calibration curve and adjusting the
counts or voltage values obtained back to the values obtained on those particular standardants during the collection of the
calibration data. The corrections are accomplished mathematically and are applied to both the slope and intercept. Improved
precision may be obtained by using a multi-point drift correction as described in Practice E1329.
3.2.5 type standardization—mathematical adjustment of the calibration curve’s slope or intercept using a single standardant
(reference material) at or close to the nominal composition for the particular alloy being analyzed. For best results the standardant
being used should be within 610 % of the composition (for each respective element) of the material being analyzed.
4. Summary of Test Method
4.1 A unipolar triggered capacitor discharge is produced in an argon atmosphere between the prepared flat surface of a specimen
and the tip of a semi-permanent counter electrode. The energy of the discharge is sufficient to ablate material from the surface of
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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the sample, break the chemical or physical bonds, and cause the resulting atoms or ions to emit radiant energy. The radiant energies
of the selected analytical lines and the internal standard line(s) are converted into electrical signals by either photomultiplier tubes
(PMTs) or a suitable solid state detector. The detector signals are electrically integrated and converted to a digitized value. The
signals are ratioed to the proper internal standard signal and converted into mass fractions by a computer in accordance with
Practice E305.
4.2 Three different methods of calibration defined in 3.2.1, 3.2.2 and 3.2.3, are capable of giving equivalent precision, accuracy
and detection limits.
4.2.1 The first method, binary calibration, employs calibration curves that are determined using a large number of high-purity
binary calibrants. This approach is used when there is a need to analyze almost the entire range of magnesium alloys. Because
binary calibrants may respond differently from alloy calibrants, the latter are used to improve accuracy by applying a slope
correction, intercept correction, or both to the observed readings.
4.2.2 The second method, global calibration, employs calibration curves that are determined using many different alloy calibrants
with a wide variety of compositions. Mathematical calculations are used to correct for both alloy difference and inter-element
effects. Like the method above, specific alloy calibrants may be used to apply a slope correction, intercept correction, or both to
the observed readings.
4.2.3 The third method, alloy calibration, employs calibration curves that are determined using various alloy calibrants that have
similar matrix compositions. Again, specific alloy calibrants may be used to apply a slope correction, intercept correction, or both
to the observed readings.
5. Significance and Use
5.1 The metallurgical properties of magnesium and its alloys are highly dependant on chemical composition. Precise and accurate
analyses are essential to obtaining desired properties, meeting customer specifications and helping to reduce scrap due to off-grade
material.
5.2 This test method is applicable to chill cast specimens as defined in Practice B953 and can also be applied to other types of
samples provided that suitable reference materials are available.
6. Interferences
6.1 Table 1 lists analytical lines commonly used for magnesium analysis. Other lines may be used if they give comparable results.
Also listed are recommended mass fraction range, background equivalent concentration (mass fraction) (BEC), detection limits,
and potential interferences where available. The values given in this table are typical; actual values obtained are dependent on
instrument design and set-up.
7. Apparatus
7.1 Specimen Preparation Equipment:
7.1.1 Sampling Molds, for magnesium the techniques of pouring a sample disk are described in Practice B953. Chill cast samples,
poured and cast as described within Practice B953 shall be the recommended form in this test method.
7.1.2 Lathe, capable of machining a smooth, flat surface on the reference materials and samples. Either alloy steel, carbide-tipped,
or carbide insert tool bits are recommended. Proper depth of cut and desired surface finish are described in Practice B953.
7.1.3 Milling Machine—A milling machine can be used as an alternative to a lathe.
7.1.4 Metallographic Polisher/Grinder—A metallographic polisher/grinder may also be used to prepare the sample surface
provided care has been taken in the selection a non-contaminating abrasive compound. Metallographic grade wet/dry silicon
carbide discs of 120 grit or higher will produce a good sample surface with essentially no silicon carryover to the sample. This
must be verified by making a comparison between freshly prepared surfaces on a polisher/grinder to that of a lathe or milling
machine. Reference Guide E1257 for a description of contamination issues with various abrasive compounds.
7.2 Excitation Source, capable of producing a unipolar triggered capacitor discharge. In today’s instrumentation the excitation
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TABLE 1 Recommended Analytical Lines
Recommended Background Detection
Wavelength in Air Interferences Element,
Element Mass Fraction Equivalent, Limit,
A
(nm) λ(nm)
B C
Range, % % %
Aluminum 396.15 I 0.001 – 0.5 0.008 0.0001* Zr 396.16
Aluminum 256.80 I 1.0 – 12.0 Zn 256.81
Ar 256.81
Aluminum 266.04 I 1.0 – 12.0
Aluminum 394.40 I 0.001 – 0.5 0.002
Aluminum 308.22 I 1.0 – 12.0 0.09 Mn 308.21
Beryllium 313.04 II 0.0001 – 0.01 0.0005 0.0001 Ag 313.00
Ce 313.09
Boron 182.64 I Co 182.60
Mg 182.68
Boron 249.68 I Fe 249.65
Fe 249.70
Al 249.71
Ce 249.75
Cadmium 226.50 II 0.0001 – 0.05 0.002 0.00005 Ce 226.49
Ni 226.45
Fe 226.44
Cadmium 228.80 I 0.00003 – 0.1 Ce 228.78
Ni 228.77
Fe 228.73
Calcium 393.37 II 0.0005 – 0.05 0.0002 0.0002 Fe 393.36
Ce 393.37
Zr 393.41
Cerium 413.77 II 0.01 – 3.0 Zr 413.74
Fe 413.78
Cerium 418.66 II 0.01 – 3.0 Dy 418.68
Chromium 425.44 I 0.0002 – 0.005 Ce 425.34
Cu 425.56
Copper 324.75 I 0.001 – 0.05 0.003 0.0001 Mn 324.75
Mn 324.85
Dysprosium 353.17 II 0.01 – 1.0 Mn 353.19
Mn 353.21
Erbium 400.80 II 0.01 – 1.0 0.08 0.001 Mn 400.80
Sm 400.81
Gadolinium 379.64 0.01 – 3.0 0.1 0.001 Zr 379.65
Iron 259.94 II 0.001 – 0.06 0.023 0.0005 Mn 259.89
Iron 238.20 II Zn 238.22
Ce 238.23
Zr 238.27
Iron 371.99 I 0.001 – 0.06 0.007 Ti 372.04
Lanthanum 433.37 II 0.01 – 1.5 0.1 0.001 Pr 433.39
Sm 433.41
Lead 368.35 I 0.005 – 0.1 Fe 368.31
Mn 368.35
Zn 368.35
Lead 363.96 I 0.05 – 0.5 Zn 363.95
Fe 364.04
Lead 217.00 I 0.005 – 0.1 0.04 Mn 216.98
Ce 216.95
Lithium 670.78 I 0.001 – 0.05
Lithium 610.36 I
Magnesium 291.55 I Internal Standard Mn 291.46
Al 291.57
Magnesium 517.27 I Internal Standard Fe 517.16
Manganese 257.61 II 0.001 – 0.5 Mn 257.57
Fe 257.69
Manganese 259.37 II 0.002 – 0.5 Mg 259.32
Zr 259.37
Fe 259.37
Manganese 293.31 II 0.001 – 2 0.12
Manganese 403.08 I 0.001 – 0.5 0.006 0.0002 Zr 403.07
Fe 403.05
Manganese 403.45 I 0.01 – 0.5
Neodymium 406.11 II 0.01 – 3.0 Mn 406.17
Nickel 231.60 II 0.001 – 0.05
Nickel 351.51 I 0.001 – 0.05 Zn 351.51
Nickel 341.48 I 0.0005 – 0.05 0.015 0.0003 Zr 341.47
Phosphorous 178.28 I 0.0002 – 0.01 0.009 0.0001 Zr 178.33
Praseodymium 422.30 0.01 – 0.5 0.1 0.001
Samarium 356.83 II 0.01 – 1.0 0.1 0.001 Fe 356.84
Silicon 251.61 I 0.002 – 1.5 0.013 Zn 251.58
V 251.61
Al 251.59
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TABLE 1 Continued
Recommended Background Detection
Wavelength in Air Interferences Element,
Element Mass Fraction Equivalent, Limit,
A
(nm) λ(nm)
B C
Range, % % %
Silicon 288.16 I 0.002 – 1.5 0.088 0.0006 Al 288.15
Silicon 390.55 I 0.5 – 5 1.0? Mn 390.50
Silver 338.29 I 0.001 – 0.2 Fe 338.24
Silver 235.79 II
Sodium 588.99 I 0.0005 – 0.01 0.0002 0.0002
Sodium 589.59 I 0.0005 – 0.01 0.0002 0.0002
Strontium 460.73 I 0.01 – 4.0 Mn 460.76
Tin 284.00 I 0.002 – 0.05 Mn 284.00
Fe 284.04
Tin 317.50 I 0.002 – 0.5 0.062 0.0004 Mn 317.47
Fe 317.54
Titanium 337.28 II 0.001 – 0.02 0.005 Zr 337.34
Ce 337.37
Yttrium 417.76 II 0.02 – 7.0 0.06 0.0005 Fe 417.76
Nd 417.73
Ytterbium 328.94 0.01 – 1.0 0.0002 0.0001 Y 328.99
Zinc 213.86 I 0.001 – 0.1 0.001 Low line Zr 213.85
Zr 213.99
Zinc 334.50 I 0.01 – 3.0 High line Al 334.45
Ce 334.48
Zr 334.48
Mn 334.54
Zinc 481.05 I 0.05 – 10.0 0.09 0.001 Nd 481.13
Zirconium 339.20 II 0.001 – 1.0 0.027 0.0002 Fe 339.20
Fe 339.23
Zirconium 343.82 II 0.001 – 1.0 Ni 343.73
Fe 343.83
Zirconium 349.62 II 0.001 – 1.0 0.005 Mn 349.58
Y 349.61
A
I = atom line, II = ion line.
B
Background Equivalent—The mass fraction at which the signal due to the element is equal to the signal due to the background.
C
In this test method, the detection limit was measured by calculating the standard deviation of ten consecutive burns on a specimen with element mass fraction(s) at levels
below ten times the expected detection limit. For the values marked with an asterisk (*) the available data was for a mass fraction greater than ten (10) times but less than
a hundred (100) times the expected detection limit.
source is computer controlled and is normally programmed to produce: (1) a high-energy pre-burn (of some preset duration), and
(2) an arc/spark-type discharge (of some preset duration) for the exposure burn during which time the analytical data is gathered
and processed by the system.
7.2.1 Typical parameters and exposure times are given in Table 2. It should be emphasized that the information presented is given
as an example only and parameters may vary with respect to instrument model and manufacturer.
7.3 Excitation Chamber shall be designed with an upper plate that is smooth and flat so that it will mate (seal) perfectly with the
prepared surface of the sample specimen. The seal that is formed between the two will exclude atmospheric oxygen from entering
the discharge chamber. The excitation chamber will contain a mounting clamp to hold the counter electrode. The excitation stand
assembly will also have some type of clamp or device designed to hold the sample firmly against the top plate. Some manufacturers
may provide for the top plate to be liquid cooled to minimize sample heat-up during the excitation cycle. The excitation chamber
will also be constructed so that it is flushed automatically with argon gas during the analytical burn cycle. The excitation chamber’s
design should allow for a flow of argon gas to prevent the deposition of ablated metal dust on the inner-chamber quartz window(s).
The excitation chamber will be equipped with an exhaust system that will safely dispose of the argon gas and the metal dust created
during the excitation cycle. For reasons of health and cleanliness, the exhausted gas and dust should not be vented directly into
TABLE 2 Typical Excitation Source Electrical Parameters
Pre-Burn: Exposure:
Parameter
Pure / Alloy Pure / Alloy
Resistance, Ω 0.5 / 0.5 0.5 / 0.5
Resistance, 0.5 / 0.5 0.5 / 0.5
Inductance, μH 920 / 20 2020 / 2020
Volts, V 400 / 450 400 / 400
Frequency, Hz 200 / 400 200 / 200
Capacitance, μF 3 / 3 3 / 2
Time, s 5 / 10 10 / 10
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the laboratory. To help with this situation, manufacturers have designed their instruments with some type of exhaust/scrubber
system to deal with this problem. The exhaust can then be vented into an efficient hood system.
7.4 Gas Flow System will be designed so that it can deliver pure argon gas to the excitation chamber. The purity of the argon gas
will affect the precision of the results. Generally, precision improves as the purity of the argon gas gets higher. Argon gas with a
minimum purity of 99.995 % has been found to be acceptable. The gas shall be delivered by a flow system as described in Practice
E406. The argon gas source can be from high-purity compressed gas cylinders, a cryogenic-type cylinder that contains liquid argon
or possibly from a central supply (liquid only). It is essential that only argon gas meeting the minimum purity of 99.995 % be used.
A lower purity grade of argon, such as a “welding grade,” should not be used. The delivery system shall be composed of a
two-stage type (high/low pressure) regulator of all-metal construction with two pressure gages. Delivery tubing must not produce
any contamination of the argon stream. Refrigerator grade copper tubing is recommended. The gages on the regulator will allow
for the adjustment of the gas pressure to the instrument. Delivery pressure specifications will vary with instrument manufacturer.
Please note that the delivery tube connections should be made with all metal seals and the delivery tubing itself should be kept
as short as possible. Argon supply shall be sufficient to support required flow during analysis and bleed during idle periods. All
connections must be leak-free.
7.5 Spectrometer—For details on describing and specifying the spectrometer of an atomic emission direct reading instrument refer
to Guide E1507.
7.6 Measuring and Control System of the instrument consists of either photomultiplier tubes with integrating electronics or
solid-state photosensitive arrays (CCD or CID) that convert observed light intensities to a digitizable signal. A dedicated computer,
microprocessor, or both are used to control burn conditions, source operation, data acquisition and the conversion of intensity data
to mass fractions. Data should be accessible to the operator throughout all steps of the calculation process. Mass fraction data may
be automatically transferred to a site computer or server for further data storage and distribution. The instrument’s control software
should include functions for routine instrument drift correction (standardization), type standardization and the application of these
functions to subsequent analyses.
8. Reagents and Materials
8.1 Counter-Electrode—The counter-electrode and specimen surface are the two terminus points of the spark discharge. The
counter electrode should be made from thoriated tungsten or silver and have a pointed end. The gap distance between the specimen
surface and the tip of the counter electrode is typically 3–5 mm and is specified by the instrument manufacturer. The diameter and
geometry of the counter electrode is also application and instrument dependent. If different designs, configurations, or both are
offered, it is recommended that the prospective purchaser test each design to determine which one performs the best for the
intended analytical task. The counter electrode configuration and auxiliary gap distance must not be altered subsequent to
spectrometer calibration or calibration adjustments. Electrode maintenance (frequent brushing of the counter electrode) is needed
to maintain its configuration, gap distance and minimize surface contamination all of which are critical to accurate, precise
analytical results. It is recommended that the purchaser specify that the instrument come with several spare counter electrodes so
that they can be replaced when necessary.
9. Reference Materials
9.1 Calibrants—All calibrants shall be homogeneous and free of cracks or porosity. These materials should also possess a
metallurgical condition that is similar to the material(s) that are being analyzed. The calibrants shall be used to produce the
analytical curves for the various elements being determined.
9.1.1 It is recommended that a calibration curve for any particular element be composed of a minimum of four calibrants. The
mass fractions of these calibrants should be fairly evenly spaced over the calibrated analytical range so that a mathematically valid
calibration curve can be established using all of the points.
9.1.1.1 The calibrants used shall be of sufficient quality, purchased from a recognized reputable source, and have certified values
to the required accuracy for the anticipated analytical tasks to be performed. Commercial sources for magnesium reference
materials are found in Appendix X1.
9.1.2 For trace elements, reference materials that contain variable mass fractions of the trace element in a typical alloy of constant
or nearly constant composition are available. These reference materials can be used for establishing the analytical curve, but will
not reveal potential interferences from nearby lines of other elements, or matrix effects that change instrument response or
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