【作者】 杨旭；

【导师】 王丙兴； 刘国怀；

【作者基本信息】 东北大学 ， 材料加工工程， 2020， 硕士

【摘要】 GH4169合金具有优异的高温综合性能,广泛用于航空航天、石油化工、核能应用等重要领域,然而该合金存在高温变形抗力高、应变硬化倾向严重等问题,采用常规方法难于生产复杂的异构零件。超塑成形技术的发展为该合金的加工成形提供了崭新途径,然而细晶GH4169合金的制备流程复杂,组织均匀性差等问题突出,同时GH4169合金的超塑性变形微观机制尚不明确,严重限制了该合金超塑性的实际应用,为解决上述问题,本文针对GH4169合金的冷轧热处理细晶工艺及超塑性变形行为进行研究,主要的研究内容和结果如下:(1)制定了 GH4169合金大变形量冷轧+两阶段退火工艺流程。确定了最佳的轧制和热处理工艺参数,简化轧制热处理工艺流程,获得了组织均匀性良好的细晶薄板产品。结果表明,对GH4169合金板材首先进行84%的冷轧变形,随后在860℃退火处理10h,接着在950℃退火处理3h,可以获得晶粒尺寸为3.56μm的细晶组织,同时均匀性良好。(2)探究了 GH4169合金在冷轧热处理过程中的组织演变规律及晶粒细化机制。分析了在不同热处理参数下δ相析出以及基体组织的变化规律,进而获得了冷轧热处理工艺条件下的晶粒细化机制。结果表明,合金内部储存的大量畸变能,在再结晶退火中提升了静态再结晶的驱动力,同时预先均匀析出的长针状δ相在再结晶退火过程中促进合金的静态再结晶形核,钉扎在晶界处阻碍晶粒长大,最终获得了晶粒细小均匀的组织。(3)研究了细晶GH4169合金的超塑性力学行为。研究了不同变形条件对合金超塑性的影响,获得了最佳的变形条件,进而获得了该合金的超塑性特征参数。结果表明,在温度为950℃和应变速率为1.6×10-3s-1的条件下,GH4169合金的超塑性延伸率最高,为756%。在950℃变形时,合金的应变速率敏感性指数为0.53,应力指数为1.89,在应变速率为4.0×10-4s-1时,合金的变形激活能为299.29kJ/mol。(4)掌握了 GH4169合金超塑性变形的组织演变规律及变形机制。在不同变形条件下,研究了合金在变形过程中的组织演变,进而获得了 GH4169合金的超塑性变形机制。结果表明,在超塑性变形后,合金内部δ相形貌主要为块状和短棒状,晶粒尺寸有所增加,并且伸长区域内部晶粒均呈现近等轴状。从力学行为与组织演变两方面考虑,晶内扩散调节的晶界滑移是GH4169合金的超塑性变形的主要机制。更多还原

【Abstract】 GH4169 superalloy has excellent high temperature comprehensive properties and is widely used in aerospace,petrochemical,nuclear energy applications and other important fields.However,this alloy has high temperature deformation resistance and serious strain hardening tendency.It is difficult to produce complex heterogeneous parts using conventional methods.The development of superplastic forming technology provides a new way for the processing and forming of this alloy.However,the preparation process of fine-grained GH4169 superalloy is complicated,and problems such as poor microstructure uniformity are prominent.At the same time,the superplastic deformation micromechanism of GH4169 superalloy is still unclear,which severely limits The practical application of the superplasticity of this alloy,in order to solve the above problems,this article focuses on the cold-rolling heat treatment of the GH4169 alloy and the superplastic deformation behavior of the study.The main research contents and results are as follows:(1)The large deformation cold rolling+two-stage annealing process of GH4169 superalloy was developed.The optimal rolling and heat treatment process parameters were determined,the rolling heat treatment process flow was simplified,and fine-grained sheet products with good structure uniformity were obtained.The results were shown that the GH4169 alloy sheet is first subjected to 84%cold rolling deformation,then annealed at 860℃ for 10h,and then annealed at 950℃ for 3h,a fine grain structure with a grain size of 3.56μm can be obtained with good uniformity.(2)The microstructure evolution law and grain refinement mechanism of GH4169 superalloy during cold rolling heat treatment were explored.The precipitation of δ phase and the change rule of matrix structure under different heat treatment parameters were analyzed,and the grain refinement mechanism under cold-rolling heat treatment process conditions was obtained.The results were shown that the large amount of distortion energy stored in the alloy enhances the driving force of static recrystallization during the recrystallization annealing,and the long needle-like δ phase uniformly precipitated in advance promotes the static recrystallization nucleation of the alloy during the recrystallization annealing process.Pinning at the grain boundary hinders the growth of grains,and finally obtains a fine and uniform structure of grains.(3)The superplastic mechanical behavior of fine-grained GH4169 superalloy was studied.The effect of different deformation conditions on the superplasticity of the alloy was studied,the best deformation conditions were obtained,and then the superplastic characteristic parameters of the alloy were obtained.The results were shown that at a temperature of 950℃ and a strain rate of 1.6×10-3s-1,the superplastic elongation of GH4169 superalloy is the highest,which is 756%.When deformed at 950℃,the strain rate sensitivity index of the alloy is 0.53 and the stress index is 1.89.When the strain rate is 4.0×10-4s-1,the deformation activation energy of the alloy is 299.29kJ/mol.(4)The microstructure evolution law and deformation mechanism of GH4169 superalloy superplastic deformation were grasped.Under different deformation conditions,the micro structure evolution of the alloy during the deformation process was studied,and the superplastic deformation mechanism of the GH4169 superalloy was obtained.The results were shown that after superplastic deformation,theδ-phase morphology inside the alloy is mainly block and short rod,the grain size increases,and the grains in the elongation zone all appear nearly equiaxed.Considering both mechanical behavior and micro structure evolution,grain boundary slip regulated by intragranular diffusion is the main mechanism of superplastic deformation of GH4169 superalloy.更多还原