The secret of adjusting the phase transition temperature of memory alloy
The transition temperature of nitinol is determined by the composition of the memory alloy.That is, when the content of nickel in the alloy increases, and the starting point and the end point of the deformation temperature of the alloy decrease. Conversely, if the content of titanium in the alloy increases, both the starting point and the end point of the alloy deformation temperature rise.
When the nickel content in the alloy is about 55%, martensite begins to form at 40 °C. Starting from 40 ° C, the alloy gradually softens and is easy to process. If the nickel content in the alloy is reduced to 54%, the temperature at which the alloy's martensite begins to form rises to 70 °C at once. Conversely, if the nickel content in the alloy is increased by 1% to 56%, then the martensite of the alloy begins to form a temperature and suddenly drops to 0 °C. When the nickel content increases by 1% to 57%, the temperature at which martensite begins to form will continue to drop, reaching -10 °C.
The effect of the alloy composition on the temperature at which the memory alloy returns to its original shape at low temperatures is also significant. The results of the experts' tests are as follows: When the atomic concentrations of nickel and titanium in the nickel-titanium alloy are equal, the end temperature of the alloy from the low temperature martensite state to the high temperature parent phase is about 100 °C. If the concentration of nickel atoms in the alloy is increased by five thousandths, the end temperature of the shape recovery drops sharply to about 20 °C. The atomic concentration corresponding to the nickel content, for each one thousandth increase, the shape of the alloy returns to the final temperature, which is reduced by about 10 °C; if the concentration of titanium atoms is increased by three thousandths, the shape of the alloy returns to the final temperature, and the temperature is increased by 30 °C. ~50 °C.
