ASTM B648-23

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Designation: B648 − 10 (Reapproved 2015) B648 − 23
Standard Test Method for
Indentation Hardness of Aluminum Alloys by Means of a
Barcol Impressor
This standard is issued under the fixed designation B648; 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.
ε NOTE—Appendix X1 was moved to appear one page in October 2015.
1. Scope
1.1 This test method covers the determination of indentation hardness of aluminum alloys using a Barcol Impressor, Model No.
934-1.Impressor.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The values
given in parentheses after SI units are provided for information only and are not considered standard.
1.2.1 Exception—The values given in parentheses are for information only.Some Barcol Impressors are for use on plastics and are
not included in this test method and should not be used for aluminum alloys.
NOTE 1—Another model, No. 935, is for use on plastics but is not included in this test method and should not be used for aluminum alloys.
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.
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:
E6 Terminology Relating to Methods of Mechanical Testing
E10 Test Method for Brinell Hardness of Metallic Materials
E18 Test Methods for Rockwell Hardness of Metallic Materials
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—The definitions of terms relating to hardness testing appearing in Terminology E6 shall be considered as
applying to the terms used in this test method.
This test method is under the jurisdiction of ASTM Committee B07 on Light Metals and Alloys and is the direct responsibility of Subcommittee B07.05 on Testing.
Current edition approved Oct. 1, 2015June 1, 2023. Published October 2015June 2023. Originally approved in 1978. Last previous edition approved in 20102015 as
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B648 – 10.B648 – 10 (2015) . DOI: 10.1520/B0648-10R15E01.10.1520/B0648-23.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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B648 − 23
FIG. 21 Diagram of Typical Barcol Impressor Arrangement
4. Significance and Use
4.1 The Barcol Impressor is portable and therefore useful for in situ determination of the hardness of fabricated parts and
individual test specimens for production control purposes.
4.2 This test method should be used only as cited in applicable material specifications.
5. Apparatus
5.1 Barcol Impressor, Model 934-1—Impressor—See Fig. 1 and Fig. 2.
5.2 Indentor—The indentor shall consist of a hardened steel truncated cone having an angle of 26° with a flat tip 0.157 mm (0.0062
in.) in diameter. It shall fit into a hollow spindle and be held down by a spring-loaded plunger. See Fig. 21.
5.3 Indicating Device—The indicating dial shall have 100 divisions, each representing a depth of 0.0076 mm (0.00030 in.)
(0.00030 in.) penetration. The higher the reading, the harder the material.
6. Test Parts or Specimen
6.1 The testing area shall be smooth, clean, and free of mechanical damage. The surface may be lightly polished to eliminate
scratches or die lines. It shall be such that it can be essentially perpendicular to the indentor during the test.
NOTE 1—The effect of curvature of the test specimen on the Barcol Impressor readings is presented in Appendix X1, Fig. X1.1.
6.2 Dimensions—Test parts or specimens shall be at least 1.5 mm ( ⁄16 in.) thick and large enough to ensure a minimum distance
of 3 mm ( ⁄8 in.) in any direction from the indentor point to the edge.
7. Calibration
7.1 With the plunger upper guide backed out until it just engages the spring, place the impressor on a glass surface and press down
until the penetrator point is forced all the way back into the lower plunger guide. The indicator should then read 100 6 1. If it
does not, loosen the locknut and turn the lower plunger guide in or out to obtain a reading of 100.
7.2 Read the hardness of a “hard” aluminum alloy reference disk supplied by the manufacturer of the impressor and, if necessary,
adjust so that the reading is within the range marked on the disk.
B648 − 23
TABLE 1 Recommended Sample Sizes to Equalize the
Variance of the Average
Hardness, Coefficient Minimum
Reading Variance of
M-934-1 of Variation, No. of
Variance Average
Scale % Readings
50 1.66 1.1 0.28 6
60 1.39 0.9 0.28 5
70 1.12 0.8 0.28 4
80 0.85 0.7 0.28 3
7.3 Repeat the process with a “soft” reference disk.
7.4 If the reference readings cannot be obtained, subsequent measurements are not valid.
8. Procedure
8.1 Support the test parts or specimens on a hard, firm surface if they are likely to bend or deform under the pressure of the
indentor (indentor. Note 3). The indentor must be perpendicular to the surface being tested.
NOTE 3—Curved surfaces may be more difficult to support. When the load is applied, bending and spring action in the part or specimen should be avoided.
8.1.1 Curved surfaces may be more difficult to support. When the load is applied, bending and spring action in the part or specimen
should be avoided.
8.2 Grasp the impressor firmly between leg and point sleeve and set both on the surface to be tested. For irregular parts or small
specimens this may require the impressor leg to be shimmed so that the indentor will be perpendicular to the test surf
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