Abstract:
The objectives of this research were to compare the transitional temperature of the nickel titanium alloy wires which had been heat treated for one and two steps and to study the relationship between the second heat treatment temperature and the transitional temperature of the heat treated nickel titanium alloy wires. Ninety pieces of one distal end of preformed Nitinol wire were cut into 4 mm. and heat treated in the vacuum porcelain furnace. The heat treatment procedure consisted of two steps. In the first step, the 90 pieces were treated together at 440 ํC for 15 minutes for relieving the internal stress. After this, the wires were randomized into 6 groups which one was a control group. The second step was the treatment at a temperature between 400-600 ํC, in increments of 50 ํC, for 10 minutes. The differential scanning calorimeter was used to measuring the transitional temperature. The t-test was used to compare the mean of each term of the transitional temperature between the control and the treatment group. The result for Ms and As temperature did not show a significant difference in the 400 ํC-treated group (p<0.05) but showed a significant difference in the other groups (P<0.05) while Mf and Af temperature showed a significant difference in every group (P<0.05). The relationship between the second heat treatment temperature and the transitional temperature of the heat treated nickel titanium alloy wires was analysed by the Pearson's product moment test. The result was the transitional temperature which consist of Ms, Mf, As and Af showed the positive correlation with the second heat treatment temperature (P<0.05).