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 an as-extruded FGH4113A Superalloy with ultrafine Grain during isothermal Forging

摘要:

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1000，1040，1080，1120℃；应变速率为0.001，0.01，0.1s-1的Gleeble热压缩试验，压缩量为60%。试验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515.375kJ/mol。慢应变速率下(0.001s-1)，试样真应力-真应变曲线呈现出稳态流变特性；快应变速率下(0.1s-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"对变形温度敏感，高的变形温度会引发γ"的溶解而导致再结晶晶粒的长大。此外，研究发现超细晶挤压态合金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试验依据。

Abstract:

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. Average grain size number is greater than 13 for the novel powder nickel-based superalloy FGH4113A after hot extrusion. As-extruded alloy has two phases microstructure of γ+γ". Fine homogenization two phases 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, 0.1s-1. Height reduction is 60% for samples under all experiment conditions. The results show that no crack was found on the surface of alloy samples under all experiment conditions, suggesting as-extruded FGH4113A alloy with ultrafine grains has a wide isothermal forging process window. The average activation energy for the alloy is 515.375kJ/mol. True stress-true strain curves show steady flow characteristic for samples with slow strain rate (0.001s-1) and the change from work hardening to recrystallization softening for samples with fast strain rate (0.1s-1). γ" is sensitive to temperature. Recrystallization grains grow obviously at high deformation temperature due to the large amount of dissolution of γ". Furthermore, the study shows that the main recrystallization way is discontinuous dynamic recrystallization for as-extruded FGH4113A alloy with ultrafine grains. This study offers experiment evidence for designing forging processing of the as-extruded FGH4113A alloy with ultrafine grains.