【国外标准】 Standard Test Method for Determination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery

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, strip specimen, or a wire, tube, or strip specimen extracted from a component; thus, it provides an assessment of 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 ensure the alloy formulation, since chemical analysis is not precise enough to adequately determine the nickel-to-titanium ratio of shape memory alloys.5.5 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 F2004. 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′s temperature or the As temperature. In contrast, the DSC method measures the start, peak, and finish 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 Af temperatures in the range of approximately –25 to 90 °C.1.1 This test method describes a procedure for quantitatively determining the martensite-to-austenite 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 (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)2 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 Af must be limited to obtain good test results. See 5.6 for details. Ruggedness 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 nonconformance 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.