| Summary: | 碩士 === 國立高雄科技大學 === 模具工程系 === 107 === In this study, a nickel-nickel-titanium alloy rod with a ratio of 55.6 wt% Ni and 55.9 wt% Ni was used. After 18 passes, a nickel-titanium rod with a diameter of 6.4 mm was rolled by a quadruple rolling mill. The material was rolled to a sheet having a thickness of 0.5 mm, and then annealed at 400 ° C, 500 ° C, and 600 ° C for 30 minutes each. According to the NiTi phase diagram, we can observe that 54.6 wt% Ni alloy starts to precipitate at 400 °C, and NiTiTi4 Ni3Ti3 at 3 °C, Ni4Ti3 gradually disappears at 600 °C, NiTi+Ni3Ti is formed, due to the formation of precipitates. It will lead to an increase in the transition temperature of the matrix phase (M phase) in the field, so the M phase transition temperature of the 55.6 wt% Ni test piece is mainly due to the amount of precipitates; while the 55.9 wt% Ni alloy is already NiTi+Ni4Ti3 at 400 °C. Ni4Ti3 disappeared until 630 °C, so the 55.9 wt% Ni test piece was NiTi+Ni4Ti3 at 400-600 °C, so the M phase transition temperature did not change much. 55.6 wt% Ni test piece, the internal hardness gradually decreased with the increase of annealing temperature. Although Ni4Ti3 precipitated, the precipitation of Ni4Ti3 is less, and the effect on hardness is small. Therefore, the decrease of hardness should be caused by the increase of annealing temperature. The decrease leads to a decrease in hardness. The hardness of the 55.9 wt% Ni test piece is reduced to a minimum at 400 ° C / 30 min. After the annealing temperature increases, the annealing time is not long, and the Ni4Ti3 grain cannot grow. After annealing at 400 ° C / 30 min, the difference in the temperature is increased, resulting in a decrease in hardness. Then, as the annealing temperature increases, the density of Ni4Ti3 increases, and the phenomenon of precipitation hardening becomes more and more obvious. At the same time, with the increase of annealing temperature, the toughness and plateau region of nickel-rich nickel-titanium alloy also increased, while the R phase appeared at the annealing temperature of 400-600 °C, and nickel-rich nickel-titanium with different annealing temperatures The alloy exhibits different characteristics, mainly the shape memory effect when the annealing temperature is greater than 400 ° C, and the superelasticity when the annealing temperature is less than 400 ° C. This study explores the rolling of nickel-rich nickel-titanium alloy to the thinnest thickness of rollable and discusses its properties and the effects of annealing treatment.
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