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| NiTi形状记忆合金热变形行为及加工图 |
| Hot Deformation Behavior and Processing Maps of NiTi Shape Memory Alloy |
| Received:December 27, 2016 Revised:January 10, 2017 |
| DOI：10.3969/j.issn.1674-6457.2017.01.008 |
| 中文关键词: NiTi形状记忆合金 热变形 本构方程 加工图 |
| 英文关键词: NiTi shape memory alloy hot deformation constitutive equation processing maps |
| 基金项目:国家自然科学基金(51164030)；江西省教育厅科技基金(GJJ13501) |
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| 中文摘要: |
| 目的 应用Gleeble 3500热模拟试验机，研究NiTi形状记忆合金在变形温度650~1000 ℃、应变速率0.001~10 s–1条件下的热变形行为，并基于动态材料模型构建合金的加工图。方法 采用包含Arrhenius项的Z参数法建立该合金的本构关系数学模型，计算变形激活能，构建应变量为0.7和1.2时的加工图，并结合微观组织观察验证加工图预测结果的准确性。结果 NiTi合金热变形激活能Q为227.9 kJ/mol。根据加工图可知，所研究NiTi合金的失稳变形工艺参数范围分别为：650~930 ℃，0.1~10 s–1和930~1000 ℃，0.3~10 s–1，对应的失稳变形机制分别为局部流动和机械失稳；适宜的变形参数工艺范围为：750~800 ℃，0.01~0.03 s–1和850~900 ℃，0.01~0.03 s–1，对应的变形机制为动态再结晶。结论 研究结果可为NiTi合金成形工艺制度的制定和优化提供理论依据。 |
| 英文摘要: |
| The isothermal compression tests were performed over the ranges of temperatures 650~1000 ℃and strain rates 0.001~10 s–1 on a Gleeble 3500 simulator. The processing map of NiTi alloy was established based on dynamic materials modeling. The constitutive equation of the alloy deformed at high temperature was established by using the Z parameters method including the Arrhenius term. The deformation activation energy of the alloy was obtained, and the processing maps with strain of 0.7 and 1.2 were constructed. The accuracy of the prediction results of processing maps was verified by microstructure observation. The results show that the flow stress increases with deformation declining and strain rate increasing. The deformation activation energy of NiTi alloy is about 227.9 kJ/mol. According to the established processing map and microstructure observation, NiTi alloy high temperature deformation mainly exist two instable deformation zones and two peak efficiency of power dissipation zones. The instable deformation zones are in the temperature ranges and the strain rate ranges of 650~930 ℃ and 0.1~10 s–1, 930~1000 ℃ and 0.3~10 s–1. The optimum deformation conditions are in the temperature ranges and the strain rate ranges of 750~800 ℃ and 0.01~0.03 s–1, 850~900 ℃ and 0.01~0.03 s–1, in which zones the thermal deformation mechanism is dynamic recrystallization. The results can provide a theoretical basis for determining and optimizing the forming parameters of NiTi alloy. |
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