用拉伸实验研究了退火温度(θan)和应力-应变循环对Ti-50.8Ni-0.3Cr合金超弹性(SE)的影响. 结果表明, 随θan升高, 应力诱发马氏体(M)相变的临界应力σM先降低后升高, 随后趋于稳定, 分别在450和600℃达到最小值(311 MPa)\linebreak 和最大值(583 MPa). 残余应变在θan=350-590℃之间变化不大, 始终保持在较低的水平; 当θan高于590℃时, 残余应变则急剧升高. 随着应力-应变循环次数(N)增加, 350和590℃退火态合金由部分非线性超弹性逐渐转变为完全非线性超弹性, 而650℃退火态合金由部分非线性超弹性逐渐转变为线性超弹性. 此外, 随N增加, 590和650℃退火态合金的能耗作用逐渐下降, 并趋于稳定, 而350℃退火态合金的能耗作用基本保持不变. 要使Ti-50.8Ni-0.3Cr合金获得良好的SE, 退火温度应低于再结晶温度.
Effects of annealing temperature (θan) and stress-strain cycle on superelasticity (SE) of Ti-50.8Ni-0.3Cr alloy were investigated by tensile test. The results show that with increasing θan, critical stress for stress-induced martensite (σM) descends firstly and then rise. The σM reaches its minimum value (311 MPa) and maximum value (583 MPa) when annealing temperature is 450 and 600℃,\linebreak respectively. When θan=350-590℃, the residual strain (εR) has no obvious change, keeps at a low value all the time. When θan>590℃, the εR rises rapidly. With increasing stress-strain cycle number (N), the alloy annealed at 350 and 590℃ transform from incompletely nonlinear superelasticity to completely nonlinear superelasticity. The alloy annealed at 650℃ transform from incompletely superelasticity to linear-like superelasticity. Moreover, with increasing N, the energy dissipation ability of the alloy annealed at 590 and 650℃ descend gradually, and tend to stability. The energy dissipation ability of the alloy annealed at 350℃ nearly keeps constant. In order to get excellent SE, the annealing temperature of Ti-50.8Ni-0.3Cr alloy should be below recrystallization temperature.
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