1、Designation: F2082 15Standard Test Method forDetermination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery1This standard is issued under the fixed designation F2082; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for determiningthe martensite-to-aust
3、enite transformation temperatures of ei-ther fully annealed or heat-treated nickel titanium alloys bymeasuring the deformation recovered during the thermal trans-formation.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach
4、system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith this standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is th
5、eresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE220 Test Met
6、hod for Calibration of Thermocouples ByComparison TechniquesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodF2005 Terminology for Nickel-Titanium Shape MemoryAlloys3. Terminology3.1 DefinitionsSpecific technical terms used in this testmethod are found
7、in Terminology F2005.3.2 free recoveryunconstrained motion of a shapememory alloy upon heating and transformation to austeniteafter deformation in a lower temperature phase.3.3 Abbreviations:3.3.1 LVDTlinear variable differential transducer.3.3.2 RVDTrotary variable differential transducer.4. Summar
8、y of Test Method4.1 This test method involves cooling a test specimen to itsnominally fully martensitic phase, deforming the specimen,and heating the specimen to its fully austenitic phase. Duringheating, the motion of the specimen is measured and plottedversus the specimen temperature. For a two-st
9、agetransformation, the Rs, Rf, As, and Af, as defined in Terminol-ogy F2005, are determined. For a single-stage transformation,the Asand Afare determined.5. Significance and Use5.1 This test method provides a rapid, economical methodfor determination of transformation temperatures.5.2 Measurement of
10、 the specimen motion closely parallelsmany shape memory applications and provides a result that isapplicable to the function of the material.5.3 This test method uses wire, tube, or strip samples; thus,it is able to provide an assessment of the product in itssemifinished form.5.4 This test method ma
11、y be used on annealed samples todetermine the transformation temperatures and assure the alloyformulation, since chemical analysis is not precise enough todetermine adequately the nickel-to-titanium ratio of shapememory alloys.5.5 Transformation temperatures derived from this testmethod may differ f
12、rom those derived from other methods as aresult of the effects of strain and load on the transformationtemperature.5.6 The test method is applicable to shape memory alloyswith Aftemperatures in the range of approximately 25 to+90C.1This test method is under the jurisdiction of ASTM Committee F04 on
13、Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved May 1, 2015. Published July 2015. Originally approvedin 2001. Last previous edition approved in 2006 as F2082 06, which waswithdrawn in January 2015 and
14、reinstated in May 2015. DOI: 10.1520/F2082-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM
15、International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Apparatus6.1 LVDT, with range greater than half the mandrel diameter(see 9.2), with power supply, mounted in an appropriate fixturewith counterbalanced probe (see Fig. 1); or RVDT with rangegreater
16、than 45, with power supply, mounted in an appropriatefixture (see Fig. 2); or a vision system; or equivalent means ofmeasuring sample displacement.6.2 Thermocouple and Indicator, with resolution of 0.1C(0.2F) or better.6.3 XY Chart Recorder, or equivalent manual or automateddata acquisition system.6
17、.4 Hot Plate and Stirrer.6.5 Bath of Heat Transfer Fluid, for example, denaturedalcohol, ethylene glycol, water, and so forth.6.6 Mandrel, for deforming the sample in the martensiticstate.6.7 Fixture, for holding the sample during recovery.6.8 Liquid Nitrogen, or dry ice.7. Sampling7.1 Test specimen
18、 can be a wire, tube, or strip with diameteror 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 diameter or thickness may be less than 0.3mm.7.2 Specimens may be tested in the semifinished (heat-treated) or
19、 annealed condition. Anneal is defined in Terminol-ogy F2005.8. Calibration8.1 The thermocouple and indicator shall be kept in acalibrated condition, traceable to the National Institute forStandards and Technology or appropriate National MetrologyInstitute that successfully participates in relevant
20、internationalinterlaboratory comparisons.8.2 The thermocouple shall be calibrated using Test MethodE220.9. Procedure9.1 For alloys that are superelastic at room temperature,cool a bath of appropriate heat transfer fluid to 55C (67F)or lower using liquid nitrogen, dry ice, or other suitablemethod. Fo
21、r alloys that are martensitic at room temperature,cool the bath to 10C (50F) or lower.9.2 Select a mandrel according to the sample diameter orthickness to give an outer fiber strain of 2 to 2.5 %. For thesestrains, mandrel diameter shall be between 39 and 49 timesspecimen diameter or thickness.9.3 C
22、ut a test specimen long enough to wrap 90 to 180around the mandrel.9.4 Place the recovery fixture and the mandrel, along withthe test specimen, in the bath and wait a minimum of 3 min forthe fixtures to equilibrate to the bath temperature.9.5 Deform the specimen in the bath by wrapping it 90 to180 a
23、round the mandrel.9.6 Place the specimen on a fixture (recovery fixture) thatholds the sample so as not to interfere with the free recovery ofthe specimen on heating.FIG. 1 Schematic Showing Side View of Test Apparatus Using a Vertically Mounted and Counterbalanced LVDT(LVDT Power Supply, Thermocoup
24、le Indicator, and Data Acquisition System are not shown)F2082 1529.7 Remove the mandrel from the bath. Alternatively, themandrel can be attached to the recovery fixture and left in thebath. In this case, the thermal mass of the mandrel and fixtureshall be such that the temperature of the fixture and
25、 the bath isuniform throughout the test.9.8 Set the device to measure the motion of the sample.9.8.1 For an LVDT, lower the LVDT core onto the specimenas shown in Fig. 3. The weight of the LVDT core shall becounterbalanced such that the weight on the specimen is nomore than 3 g.FIG. 2 Schematic Show
26、ing Top View of Test Apparatus Using an RVDT(RVDT Power Supply, Thermocouple Indicator, and Data Acquisition System are not shown)FIG. 3 Placement of LVDT Core on Deformed Specimen, Which Is Resting on Recovery Fixture PinsF2082 1539.8.2 For an RVDT, make sure that the needle is in contactwith the t
27、est specimen (Fig. 4). To minimize friction effects, theneedle shall be encased in a polytetrafluoroethylene (PTFE)sheath, or the needle shall be constructed from or coated withPTFE or material with equivalent friction.9.9 Place the thermocouple in the bath as close to thespecimen as is practical.9.
28、10 Set the XY chart or data acquisition system to recordthe temperature on the either X or Y axis and sample motion onthe other axis.9.11 Stir and heat the bath on the hot plate to a temperatureabove the Af. Limit the heating rate to no more than 4C/minduring the recovery.9.12 Stop the test once the
29、 temperature is at least 10Cabove the Af, as determined by noting that the sample isstraight and the displacement-versus-temperature curve hasflattened. Turn off the hot plate and stop recording.10. Determination of Transformation Temperature10.1 Determine the transformation temperatures accordingto
30、 Fig. 5 or Fig. 6. The transformation may occur in one or twostages. For a one-stage transformation, the middle tangent lineshould be drawn tangent to the steepest portion of the curve(see Fig. 5). In the case of a two-stage transformation, one lineshould be drawn tangent to the steepest slope obser
31、ved in thefirst stage of the transformation, and a second line should beFIG. 4 Placement of Needle on Deformed Specimen, Clamped to the Recovery Fixture. Top View Shown with Stylus and RVDT Re-moved. Note the Recommended RVDT Axis Location Is Offset from the Mandrel by the Radius of the NeedleFIG. 5
32、 One-Stage TransformationTangent Lines and Transformation TemperaturesF2082 154drawn tangent to the steepest slope in the second stage of thetransformation (see Fig. 6).11. Report11.1 The report shall include the following information:11.1.1 Complete identification of the material tested includ-ing
33、specification, lot number, and heat treatment.11.1.2 Results of the transformation measurements, reportedto the nearest 1C.12. Precision and Bias12.1 An interlaboratory study was conducted in accordancewith Practice E691 in six laboratories with two differentmaterials, with each laboratory obtaining
34、 five results for eachFIG. 6 Two-Stage TransformationTangent Lines and Transformation TemperaturesTABLE 1 Repeatability and Reproducibility for Asof Cold-Worked and Stress-Relieved MaterialMaterial As,grandmeanRepeatabilitystandarddeviationReproducibilitystandarddeviationRepeatability Reproducibilit
35、yA 29.0 1.4 3.4 4.1 9.5B 12.4 2.5 4.5 6.9 12.5TABLE 2 Repeatability and Reproducibility for Afof Cold-Worked and Stress-Relieved MaterialMaterial Af,grandmeanRepeatabilitystandarddeviationReproducibilitystandarddeviationRepeatability ReproducibilityA 11.7 1.8 4.5 4.9 12.7B 2.9 1.5 4.8 4.3 13.6TABLE
36、3 Repeatability and Reproducibility for Asof Annealed MaterialMaterial As,grandmeanRepeatabilitystandarddeviationReproducibilitystandarddeviationRepeatability ReproducibilityA 25.4 1.4 2.2 4.1 6.3B 0.2 1.9 2.7 5.3 7.7TABLE 4 Repeatability and Reproducibility for Afof Annealed MaterialMaterial Af,gra
37、ndmeanRepeatabilitystandarddeviationReproducibilitystandarddeviationRepeatability ReproducibilityA 18.6 1.7 2.4 4.6 6.8B 8.3 0.9 1.7 2.7 4.8F2082 155material. There were two rounds of testing. In the first round,the test samples were cold-worked and stress-relieved; in thesecond round, the samples w
38、ere fully annealed. The details aregiven in Research Report No. F041009.312.2 The results of round one are shown in Table 1 andTable 2 for each transformation temperature (As,Af). Thevalues are in degrees Celsius. The terms repeatability limit andreproducibility limit are used as specified in Practi
39、ce E177.12.3 The results of round two are shown in Table 3 andTable 4 for each transformation temperature (As,Af). Thevalues are in degrees Celsius. The terms repeatability limit andreproducibility limit are used as specified in Practice E177.12.4 BiasNo measurement of bias is possible with this tes
40、tmethod because there is no accepted reference material ormethod.13. Keywords13.1 free recovery; nickel titanium; nitinol; shape memory;transformation temperatureAPPENDIX(Nonmandatory Information)X1. RATIONALEX1.1 Transformation temperature is used to characterizenickel-titanium alloys in the form o
41、f raw material, semifinishedmaterial, and finished product. In the case of raw material,transformation testing is necessary because chemical analysisis not precise enough to predict the desired shape memory andsuperelastic properties.X1.2 This test method provides a rapid, economical meansof determi
42、ning the martensitic-to-austenitic transformationtemperatures by recording the motion of the samples as itexhibits the shape memory effect. In the case of finishedproducts, this test method often is used to determine the shapememory behavior of the product in its final application.X1.3 Transformatio
43、n temperatures measured by this testmethod will differ from those measured by thermal analysis orother techniques as a result of the effects of strain and load.X1.4 A strain level of 2 to 2.5 % is selected to minimize theeffect of strain on the transformation temperatures.X1.5 The heating rate is li
44、mited to minimize the thermalgradients in the bath. The heating rate may be controlledmanually or through the use of a temperature controller.X1.6 The thermal mass of the fixture inside the bath shouldbe minimized so that the fixture and the bath are uniform.X1.7 Samples larger than 3 mm in thicknes
45、s or diameter canbe tested with this test method with the addition of a fixture toaid in the deformation of the sample. A vision system isrecommended for samples less than 0.3 mm, because friction inan RVDT or LVDT system may create a stress in the specimen.ASTM International takes no position respe
46、cting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This st
47、andard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM Internat
48、ional Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown belo
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