Influence of Fe and Nb Addition on Two-Way Shape Memory Effect of TiNi Shape Memory Alloy Rings

The influence of pre-strains and number of thermal cycling on the two-way shape memory strains of TiNi,TiNiFe and TiNiNb alloy rings were investigated to provide theoretical basis for their applications in engineering.The results indicate that the two-way memory strains of TiNi alloy rings deformed at temperature less than Mf point increase with the increase of thermal cycling number within the range of 10.4%~13.8% pre-strains.The maximum two-way memory strain of 4.15% is obtained at pre-strain of 13.8% and thermal cycling number up to 4.And when Fe or Nb atoms are added to TiNi alloys,the two-way memory strains of alloy rings first increase and then decrease at the ranges of 10.71%~15.18% pre-strains,their maximums are 3.14% and 2.56%,respectively.At the same pre-strain and thermal cycling number,the two-way memory strains of TiNi alloy rings are the greatest,after pre-strain and cycling number are more than 12.50% and 2,the two-way memory strains of TiNiFe rings rapidly rise and are greater than that of TiNiNb alloy rings.