The Effect of Specimen Size on the B2⇆B19 Martensitic Transformation under Quasi-Static Condition in 49.5Ti-40Ni-10Cu-0.5Al(at%) Alloy

Distinction between Thermal and Stress-Induced Martensitic Transformations and Inhomogeneity in Internal Stress

“…In fact, the present author and coworkers have recently found through DSC measurement that the characteristics of thermoelastic MTs in some shape memory alloys have altered with specimen size (mass). 4,5,[15][16][17] Here, the specimen size concerned is of millimeter scale. No other researcher has systematically investigated the effect of specimen size on transformation behavior.…”

“…The effect of specimen mass on transformation temperatures has thus far been investigated for transformations between B2 parent and B19' monoclinic martensite in a polycrystalline Ti-50 mol%Ni alloy, 15,16) between B2 parent and B19 orthorhombic martensite in a polycrystalline 49.5Ti-40Ni-10Cu-0.5Al (mol%) alloy, 17) between β 1 parent (D0 3type ordered structure) and β 1 martensite (18R 1 -type longperiod stacking-order [LPSO] structure in Ramsdell notation) in a single crystal of a Cu-13.4Al-4.2Ni (mass%) alloy, 4,5) and so forth. As a result, in any of these alloys, TIMT characteristics have been found to alter with specimen mass as follows.…”

“…Incidentally, transformation temperatures will shift also with scanning rate dT /dt, especially in a large specimen, probably because of inhomogeneity in temperature. As for Ti-50 mol%Ni 16) and 49.5Ti-40Ni-10Cu-0.5Al (mol%) 17) alloys, transformation temperatures of specimens of various mass have been already investigated as a function of scanning rate. By extrapolating the obtained dT /dt dependence of the MT characteristics to dT /dt = 0, the one under infinitesimally slow dT /dt, that is, under quasistatic condition (QSC), has been deduced.…”