Acta Metallurgica Sinica (English Letters) ›› 1992, Vol. 5 ›› Issue (4): 231-235.

• Research paper • Previous Articles     Next Articles

HYSTERESIS OF PHASE TRANSFORMATION TEMPERATURE IN NiTi SHAPE MEMORY ALLOY

QIN Guiying YU Xuejie JIN Heng WANG Jingcheng Shanghai Iron and Steel Research Institute,Shanghai,China   

  • Received:1992-08-25 Revised:1992-08-25 Online:1992-08-25 Published:2009-10-10

Abstract: The relationship between structure and hysteresis of phase transformation temperature in NiTi shape memory alloy has been investigated by means of TEM observation,positron an- nihilation and electrical resistivity measurement.The sequence of hysteresis for the alloy aged under different regimes was found to be:plate martensite>R-phase>tie-like martensite. The reversible displaeement of phase boundaries of these transformations is blocked by the co- herent stress field around Ti_(11)Ni_(14)phase particles.A linear relationship between S paramet- er of positron annihilation and maximum values of temperature hysteresis showed that the mismatch dislocation and elastic stress field established by Ti_(11)Ni_(14)phase precipitation are the main factor to determine the temperature hysteresis of phase transformation in NiTi shape memory alloy.

Key words: shape memory alloy, hysteresis of phase transformation temperature, coherent stress field, mismatch dislocation