气阀合金Ni30热压缩变形的流变应力行为

FLOW STRESS BEHAVIOR OF VALVE ALLOY Ni30 UNDER HOT COMPRESSION

选用真空感应冶炼+锻造工艺制成的Ni30合金锻棒作为实验材料,在合金锻棒上沿轴线方向切取Φ10 mm×17 mm的试样,再机加工成Φ8 mm×15 mm的小圆柱试样,通过Gleeble 1500热模拟实验机进行热压缩实验,应变速率分别为5 s^(-1)、20 s^(-1)、50 s^(-1),变形温度分别为1000℃、1050℃、1100℃,应变量0.5,升温速率10℃/s,保温时间5 min,热压缩实验结束后马上对试样进行水冷处理。采用Origin2019b软件处理Ni30合金热压缩实验得到的数据,并绘制真应力-真应变曲线。建立了描述合金的热变形温度、应变速率和流变应力三者的关系的本构方程ε=2.14×10^(10)[sinh(0.0029σ)]^(3.57)exp[-240190/(R T)],通过本构方程同时反映了材料的加工硬化和再结晶软化之间的动态平衡关系,并得到其热变形激活能为240.19 kJ/mol;通过观察热变形后的合金微观组织变化发现,减小应变速率或提升变形温度均能提高合金的再结晶程度。

In this paper,the Ni30 alloy forging bar made by vacuum induction smelting and forging was selected.The sampleΦ10 mm×17 mm was cut from the alloy forging bar along the axis direction,and then machined into small cylindrical sampleΦ8 mm×15 mm.The hot compression experiment was carried out by Gleeble-1500 thermal simulation experimental machine.The experimental strain rates are 5 s^(-1),20 s^(-1)and 50 s^(-1),and the deformation temperatures are 1000℃,1050℃and 1100℃,respectively,with the dependent variable of 0.5.The heating rate of the hot compression test was 10℃/s,and the holding time was 5 mins.The samples were water-cooled immediately after the hot compression test.Origin2019b software was used to process the data obtained from the Ni30 alloy hot compression experiment,and the true stress-strain curve was fitted.The relationship between thermal deformation temperature,strain rate and flow stress of the alloy is described by the constitutive equation,which wasε=2.14×10^(10)[sinh(0.0029σ)]^(3.57)exp[-240190/(R T)].It also reflects the dynamic equilibrium relationship between work hardening and recrystallization softening of the material.According to the constitutive equation established,the hot deformation activation energy of the alloy is 240.19 kJ/mol.Through the observation of the microstructure changes of the alloy after thermal deformation,it is found that the recrystallization degree of the alloy can be improved by decreasing the strain rate or increasing the deformation temperature.