超细晶挤压态FGH4113A高温合金等温锻造过程中的本构特性及组织演变

Constitutive Characterization and Microstructure Evolution of As-extruded FGH4113A Superalloy with Ultrafine Grain During Isothermal Forging

锻造是先进航空发动机粉末涡轮盘制备的关键成型工艺。合金的化学成分和挤压工艺很大程度上决定了挤压态合金的组织。新型镍基粉末高温合金FGH4113A(WZ-A3)热挤压之后晶粒度达到13级以上,挤压态合金呈现γ+γ'双相组织。细小均匀的双相组织为更为广阔的等温锻造工艺窗口提供可能。本研究采用超细晶挤压态合金FGH4113A进行温度分别为1000、1040、1080和1120℃,应变速率为0.001、0.01和0.1 s-1的Gleeble热压缩试验,压缩量为60%。结果表明合金试样在所有压缩条件下均未发生开裂,体现超细晶挤压态合金FGH4113A有广阔的等温锻造工艺窗口。合金的平均激活能仅为515.375 kJ/mol。低应变速率下(0.001 s^(-1)),试样真应力-真应变曲线呈现出稳态流变特性;高应变速率下(0.1 s^(-1)),试样的真应力-真应变曲线呈现出加工硬化到再结晶软化的变化。γ'相对变形温度敏感,高的变形温度会引发γ'相的溶解而导致再结晶晶粒的长大。此外,超细晶挤压态合金FGH4113A在等温锻造过程中主要再结晶方式为不连续动态再结晶。本研究为超细晶挤压态合金FGH4113A的锻造工艺制定提供了实验依据。

Forging is the key forming process for producing advanced aero-engine powder turbine disks.The microstructure of as-extruded alloy mostly depends on the chemical composition of alloy and extrusion processing parameters.The average grain size number is greater than 13 for the novel powder nickel-based superalloy FGH4113A after hot extrusion,and the as-extruded alloy has dual-phase microstructure ofγ+γ'.The fine and homogeneous dual-phase microstructure makes it possible to broaden isothermal forging processing window.In this study,Gleeble hot compression experiments for as-extruded FGH4113A alloy with ultrafine grains were carried out at temperatures of 1000,1040,1080,1120℃and strain rates of 0.001,0.01,0.1 s-1.Height reduction was 60%for samples under all experiment conditions.The results show that no crack is found on the surface of alloy samples under all experiment conditions,suggesting that the as-extruded FGH4113A alloy with ultrafine grains has a wide isothermal forging process window.The average activation energy for the alloy is 515.375 kJ/mol.True stress-true strain curves show a steady flow characteristic for samples under low strain rate(0.001 s^(-1))and the change from work hardening to recrystallization softening for the samples under high strain rate(0.1 s^(-1)).γ'is sensitive to temperature,and recrystallization grains grow obviously at high deformation temperature due to the dissolution of a large amount ofγ'.Furthermore,the main recrystallization way is discontinuous dynamic recrystallization for as-extruded FGH4113A alloy with ultrafine grains.This study offers experiment evidence for forging processing design of the as-extruded FGH4113A alloy with ultrafine grains.