摘要
目的以来源于挤压坯料的纯镍N6作为研究对象,分析其高温压缩变形行为及微观组织演化,为挤压工艺参数设计提供有效依据。方法利用Gleeble-1500D热-力模拟试验机,对实验样品在温度900~1200℃和应变速率0.01~10 s-1范围进行热压缩变形,获得了材料真应力-真应变曲线,利用光镜观察了变形后的微观组织。结果建立了双曲正弦函数形式的本构方程,得到材料的本构参数为Q=272.77 k J/mol,α=0.01024 MPa-1,n=4.045。基于动态材料模型建立了材料的热加工图,判断材料具有低温低应变速率和高温高应变速率2个适宜的加工区间。结论纯镍N6极易发生晶粒长大,温度和应变速率对变形组织影响显著,在变形条件为1200℃/1 s-1时,晶粒平均尺寸已经到达84.83μm。加工图失稳区间内的微观组织呈现不均匀性,为粗大变形晶粒与细小再结晶晶粒混杂的两级结构,因此在热挤压加工工艺设计中需要避开相应的参数区域。
ABSTRACT:Hot deformation behavior and microstructure evolution of nickel N6 from extrusion billet were studied to help design extrusion process. Specimens were tested at temperature range of 900~1200 ℃ and strain rate range of 0.01~10 s-1 on Gleeble-1500D thermal-mechanical testing device and true stress-strain curves were obtained. Microstructure after deformation was also studied using optical microscope. Hyperbolic-sine and Arrhenius-type constitutive model were obtained with whose parameters of Q=272.77 kJ/mol,α=0.01024 MPa-1,and n=4.045. Processing map was made using DMM model that concluded there were two regions suitable for material processing. Grain size of nickel N6 was prone to grow and significantly impacted by temperature and strain rate. When material was deformed at 1200℃/1 s-1,average grain size was up to 84.83μm. When the material was deformed,the microstructure in the region of instability exhibited in homogeneity with big coarse grains and fine DRX grains,so related regions should be avoided during hot extrusion.
出处
《精密成形工程》
2016年第3期1-6,共6页
Journal of Netshape Forming Engineering
基金
国家自然科学基金(51275270)
关键词
纯镍
热压缩
本构模型
组织演化
加工图
pure nickel
hot compression
constitutive model
structural evolution
processing map
