Nb-10Zr合金的热变形行为、组织特征及热加工图

Hot Deformation Behavior， Microstructure， and Processing Map of Nb-10Zr Alloy

摘要:

Nb-10Zr合金可作为特种薄膜功能材料应用于太阳能行业。深入理解Nb-10Zr合金的热变形行为是实现该应用的前提，然而国内目前围绕该合金热加工过程的材料加工性能相关研究十分匮乏。建立热材料加工图可实现描述指定条件下的材料可加工性，明确合金的变形窗口，指导材料加工工艺的制定和优化。选用均匀化处理后的电铸熔炼铸锭Nb-10Zr合金，采用热模拟试验机开展了热模拟压缩试验，并基于动态材料模型，通过对应变速率敏感系数m、功率耗散系数η和失稳系数ξ的数据分析，建立了材料不同温度和应变速率条件下的流变稳态区和非稳态区的热加工图。同时，通过微观组织观察，分析和验证了加工图的准确性。研究结果表明，Nb-10Zr合金铸锭在1 300 ℃下经24 h均匀化处理后，未出现Zr元素偏聚所形成的缺陷，也未见裂纹、气孔、疏松和夹渣等其他类型的缺陷。铸态组织中存在粗大晶粒和细小晶粒，晶粒尺寸分别为 500—800 μm和 20—30 μm。在应变为0.4和0.6条件下，Nb-10Zr合金存在2个合理的热加工窗口，即变形温度1 060—1 100 ℃和应变速率0.01—0.04 s^-1，以及变形温度1 080—1 100 ℃和应变速率0.3—1 s^-1。在不同变形条件下，变形后的Nb-10Zr合金均获得了细小的动态再结晶组织。在温度1 100 ℃和应变速率0.01 s^-1下，合金晶粒尺寸为80—100 μm；而在温度1 100 ℃及应变速率1 s^-1下，合金晶粒尺寸为40—60 μm。此外，通过不同工艺制备参数下合金组织形貌的观察，证明了所确定加工窗口的合理性 。本研究为Nb-10Zr生产过程中的工艺选择和工艺参数的优化提供了理论指导。

Abstract:

To elucidate the hot deformation behavior of Nb-10Zr alloy， thermal simulation compression tests were conducted using a Gleeble-1500 thermal simulation testing machine. The effects of deformation parameters such as deformation degree， deformation temperature， and strain rate on the microstructure and processability of Nb-10Zr alloy were systematically investigated， the stability regions and instability regions of the flow with various temperatures and strain sates were analyzed， the processing maps based on a dynamic material model were established for designing and improveing materials processing. Through analysis of experimental data， such as the strain rate sensitivity of the flow stress， the power dissipation efficiency η and the instability parameter ξ， the deformation window of the alloy was clarified， and the accuracy of the processing map was analyzed and verified through microstructure. The results showed that： the Nb-10Zr ingot which melted by vacuum consumable electro-arc furnace， was suffered the homogenization treatment at 1 300 ℃ for 24 h. The composition segregation and other defects could not be found in the ingot. There are coarse and fine microstructures in the ingot， and its grain sizes are 500—800 μm and 20—30 μm separately； Under 0.4 and 0.6 strain conditions， there are two reasonable hot working windows for the Nb-10Zr alloy： deformation temperature range of 1 060 to 1 100 ℃ and the deformation rate range of 0.01 to 0.04 s^-1； deformation temperature range of 1 080 to 1 100 ℃ and the deformation rate range of 0.3 to 1 s^-1. Under the above deformation conditions， the Nb-10Zr exhibits fine dynamic recrystallized microstructures. For instance， the grain size is 80—100 μm at 1 100 ℃ and 0.01 s^-1； and the grain size is 40—60 μm at 1 100 ℃ and 1 s^-1. The results were confirmed the rationality of the determined processing window. The research was provided the theory instruction for follow-on production.