ASTM F2082/F2082M-23

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Designation: F2082/F2082M − 16 F2082/F2082M − 23
Standard Test Method for
Determination of Transformation Temperature of Nickel-
Titanium Shape Memory Alloys by Bend and Free Recovery
This standard is issued under the fixed designation F2082/F2082M; 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 a procedure for quantitatively determining the martensite-to-austenite transformation temperatures
of either fully annealed or heat-treated nickel titanium alloys by or the martensite to R-phase transformation temperature of
annealed, aged, shape-set, or tempered nickel-titanium alloy specimens by deforming the specimen in bending and measuring the
deformation recovered during heating through the thermal transformation. transformation (BFR method). See 3.1.1.
NOTE 1—For aged, shape-set, or tempered specimens the transformation may be from martensite to austenite or from martensite to R-phase. See Reference
(1) for details.
1.2 The test specimen may be wire, tube, or strip or a specimen extracted from a semifinished or finished component.
1.2.1 For specimens not in the form of a wire, tube, or strip that are extracted from semifinished or finished components, a wire,
tube, or strip shaped test specimen shall be made from the component such that the deformation mode in the test specimen is pure
bending.
1.2.2 Other specimen geometries or displacements resulting in a more complex strain state, such as bending with torsion or
buckling, are beyond the scope of this standard.
1.3 Ruggedness tests have demonstrated that sample A must be limited to obtain good test results. See 5.6 for details. Ruggedness
f
tests have demonstrated that deformation strain, deformation temperature, and equilibration time at the deformation temperature
must be controlled to obtain good test results. See 9.1, 9.2, and 9.4 for details.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformancenonconformance with this standard.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 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.
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.15 on Material Test Methods.
Current edition approved April 1, 2016Oct. 15, 2023. Published May 2016October 2023. Originally approved in 2001. Last previous edition approved in 20152016 as
F2082 – 15.F2082/F2082M – 16. DOI: 10.1520/F2082_F2082M-16.10.1520/F2082_F2082M-23.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2082/F2082M − 23
2. Referenced Documents
2.1 ASTM Standards:
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
F2004 Test Method for Transformation Temperature of Nickel-Titanium Alloys by Thermal Analysis
F2005 Terminology for Nickel-Titanium Shape Memory Alloys
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 Definitions—Specific technical terms used in this test method are found in Terminology F2005.
3.1.2 free recovery—recovery, n—unconstrained motion of a shape memory alloy specimen upon heating and transformation to
austenite or R-phase after deformation in a lower temperature phase.at a temperature below the temperature for the start of the
formation of martensite, M .
s
3.1.3 A —austenite finish temperature of a finished wire, tube, or component measured by bend and free recovery using the 95
f-95
percent recoverable deformation methodology.
3.1.4 A —austenite finish temperature of a finished wire, tube, or component measured by bend and free recovery using the
f-tan
tangent methodology.
3.2 Abbreviations:
3.2.1 LVDT—linear variable differential transducer.
3.2.2 RVDT—rotary variable differential transducer.
4. Summary of Test Method
4.1 This test method involves cooling a test specimen to its nominally fully martensitic phase, a temperature below the start
temperature for the reversion to austenite, A , or to below the start temperature for the reversion to R-phase, R' , if there is an
s s
intermediate R-phase, deforming the specimen, and heating the specimen to its fully austenitic phase. During heating, the motion
of the specimen is measured and plotted versus the specimen temperature. For a two-stage transformation, the R’R' ,R’R' ,A , and
s f s
A , as defined in Terminology F2005, are determined using the tangent methodology. For a single-stage transformation, the A and
f s
A are determined using the tangent methodology. Alternatively, for either single or two-stage transformation material, the A may
f f
be measured using the 95 percent recoverable deformation methodology.
5. Significance and Use
5.1 This test method provides a rapid, economical method for determination of transformation temperatures.
5.2 Measurement of the specimen motion closely parallels many shape memory applications and provides a result that is
applicable to the function of the material.
5.3 This test method uses a wire, tube, or strip samples; thus, it is able to provide strip specimen, or a wire, tube, or strip specimen
extracted from a component; thus, it provides an assessment of the a nickel titanium product in its semifinished or finished form.
5.4 This test method may be used on annealed samples to determine the transformation temperatures and assureensure the alloy
formulation, since chemical analysis is not precise enough to determine adequately determine the nickel-to-titanium ratio of shape
memory alloys.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
F2082/F2082M − 23
5.5 Transformation temperatures derived from this test method may differ from those derived from other methods as a result of
In general, the transformation temperatures measured by this method will not be the same as those measured by the DSC method
defined in Test Method F2004the effects of strain and load on the transformation temperature. Therefore, the results of DSC and
BFR cannot be compared directly.
5.5.1 The BFR method measures the transformation temperatures by tracking shape recovery of stress-induced martensite
deformed below the R' temperature or the A temperature. In contrast, the DSC method measures the start, peak, and finish
s s
temperatures of the thermal transformation of martensite to R-phase or to austenite. See Refs (1-4).
5.6 The test method is applicable to shape memory alloys with A temperatures in the range of approximately –25 to
f
6 90°C.90 °C.
6. Apparatus
6.1 LVDT, with range greater than half the mandrel diameter (see 9.2), with power supply, mounted in an appropriate fixture with
counterbalanced probe (see Fig. 1); or RVDT with range greater than 45°, with power supply, mounted in an appropriate fixture
(see Fig. 2); or a vision system; or equivalent means of measuring sample displacement.
6.2 Thermocouple and Indicator, with resolution of 0.1°C (0.2°F)0.1 °C [0.2 °F] or better.
6.3 XY Chart Recorder, or equivalent manual or automated data acquisition system.
6.4 Hot Plate and Stirrer.
6.5 Bath of Heat Transfer Fluid, for example, denatured alcohol, ethylene glycol, water, and so forth.or water, or a fluid agreed
upon between the customer and supplier.
FIG. 1 Schematic Showing Side View of Test Apparatus Using a Vertically Mounted and Counterbalanced LVDT
(LVDT Power Supply, Thermocouple Indicator, and Data Acquisition System are not shown)
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FIG. 2 Schematic Showing Top View of Test Apparatus usingUsing an RVDT
(RVDT Power Supply, Thermocouple Indicator, and Data Acquisition System are not shown)
6.6 Mandrel, for deforming the sample in the martensitic state.
6.7 Fixture, for holding the sample during recovery.
6.8 Liquid Nitrogen, or dry ice.
7. Sampling
7.1 Test specimen canThe test specimen shall be a wire, tube, or strip with diameter or thickness in the range of 0.3 to 3.0 mm
(0.012 to 0.12 in.). For test systems that do not contact the specimen (for example, vision system), the strip, or a wire, tube, or
strip specimen extracted from a component with the specimen diameter or thickness may be less than 0.3 mm.in the range of 0.3
to 3.0 mm [0.012 to 0.12 in.].
7.1.1 For test systems that do not contact the specimen (for example, vision system), the diameter or thickness of the specimen
may be less than 0.3 mm.
7.2 Specimens mayshall be tested in the semifinished (heat-treated) or annealed condition. Anneal is annealed, aged, shape-set,
or tempered condition as defined in Terminology F2005. and required by the product specification.
8. Calibration
8.1 The thermocouple and indicator shall be kept in a calibrated condition, traceable to the National Institute for Standards and
Technology or appropriate National Metrology Institute that successfully participates in relevant international interlaboratory
comparisons.
8.2 The thermocouple shall be calibrated using Test Method E220.
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9. Procedure
9.1 For alloys that are superelasticaustenitic at room temperature, cool a bath of appropriate heat transfer fluid to –55°C
(–67°F)–55 °C [–67 °F] or lower using liquid nitrogen, dry ice, or other suitable method. For alloys that are martensitic or R-phase
at room temperature, cool the bath to 10°C (50°F)10 °C [50 °F] or lower.
9.2 Select a mandrel according to the sample diameter or thickness to give an outer fiber strain of 2 to 2.5 %. For these strains,
mandrel diameter shall be between 39 and 49 times specimen diameter or thickness.
NOTE 2—Outer fiber strain, e%, is calculated as follows: e% (decimal equivalent) = r / (r + R), where r = radius or half thickness of the test specimen
and R = radius of the mandrel. See Ref (5).
9.3 Cut a test specimen long enough to wrap 90 to 180° around the mandrel.
9.4 Place the recovery fixture and the mandrel, along with the test specimen, in the bath and wait a minim
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