Standard Test Method for Determination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery

Importancia y uso:

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 A_s 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 A_f temperatures in the range of approximately –25 to 90 °C.

Subcomité:

F04.15

Referida por:

F2516-22

Volúmen:

13.01

Número ICS:

77.120.50 (Titanium and titanium alloys)

Palabras clave:

free recovery; nickel titanium; nitinol; shape memory; transformation temperature;