基于DIC的退火NiTi形状记忆合金力学性能研究

    Study on Mechanical Properties of Annealed NiTi Shape Memory Alloy Based on DIC

    • 摘要: 应用单向拉伸试验研究了轧制方向和退火温度对Ni-55.7Ti形状记忆合金板材试样力学性能的影响。试验中,采用二维数字图像相关法(DIC)测量了加载、卸载过程中的变形信息。结果表明:未退火试样中,沿轧制方向的NiTi合金试样抗拉强度最高,极限应变最小;与轧制方向呈45°的NiTi合金试样可恢复应变比为86.68%,超弹性特性最优,但单位体积循环耗能能力不足。退火试样中,500、700 ℃退火态试样具有优异的极限变形能力,且抗拉强度较高;经400、500 ℃退火,试样失去超弹性;600~800 ℃退火态试样有良好的非线弹性恢复,残余应变均小于1.0%,超弹性性能良好;经800 ℃退火态试样的σMs最大,可恢复应变比可达98.58%,超弹性最好。

       

      Abstract: The effects of rolling direction and annealing temperature on the mechanical properties of Ni-55.7Ti shape memory alloy sheets were studied by uniaxial tensile test. In the experiment, the two-dimensional digital image correlation method (DIC) was used to measure the deformation information in the process of loading and unloading. The results show that among the unannealed specimens, the tensile strength of the NiTi alloy specimen along the rolling direction is highest and the ultimate strain is smallest. The recovery strain ratio of the NiTi alloy specimen with 45° to the rolling direction is 86.68%, and the superelastic property is best, but the energy dissipation capacity per unit volume cycle is insufficient. Among the annealed specimens, the annealed specimens at 500 ℃ and 700 ℃ have excellent ultimate deformability and high tensile strength. The specimens annealed at 400 ℃ and 500 ℃ lose superelasticity. The specimens annealed at 600-800 ℃ have good nonlinear elastic recovery, the residual strain is less than 1.0%, and the superelasticity is good. The σMs of the specimens annealed at 800 ℃ is largest, the recoverable strain ratio can reach 98.58%, and the superelasticity is best.

       

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