Physical Simulation Study And Application Of K4169 Nickel Base Superalloy For Precision Forming

Aeroengine is usually a large and complex investment casting.Because of the complex structure of the casting and the uneven cooling rate of each part of the casting,the alloy shrinks unevenly during solidification.Ultimately,the size and shape of the final castings do not conform to the pre-designed drawings,and the size difference between the final castings and the design drawings is generally referred to as the size displacement deviation.The dimensional accuracy of castings affects the quality of castings,the selection of processing technology and the assembly of final products.Although the causes of dimensional accuracy of investment casting are complex,the most important reason is the spontaneous thermal stress caused by the solidification and cooling process of metals and their alloys.This is supported by considerable background factors to understand and reveal the general rule of dimensional deviation caused by thermal stress in casting.The choice of material processing technology will further affect the micro-structure and macro-properties of materials,especially the mechanical properties.For nickel-based superalloys,the evolution mechanism of dendrites determines the mechanical properties of the alloys.However,dendrite growth occurs in the solidification stage of the solid-liquid phase of nickel-based superalloys,and can not be observed by direct detection.Therefore,in order to establish the relationship between"process-structure-performance",a new research scheme needs to be developed and discussed,so as to better reveal the solidification problem of nickel-based superalloys.In this study,as-cast K4169 superalloy was chosen as the material,and the characteristic castings of aeroengine were taken as the research object.By means of combining modern physical technology with computer numerical simulation,two major problems,namely,dimensional accuracy of castings and evolution of solidification structure,are studied.The main conclusions of this subject are as follows:1.By means of physical simulation,the processing technology of K4169 alloy in investment casting can be reproduced,and high temperature mechanical parameters such as Young's modulus,tensile strength and yield strength can be obtained.The high temperature plasticity of K4169 alloy was also discussed from the aspects of tensile fracture and section shrinkage,combined with the hardening coefficient of K4169 alloy.2.The mechanical properties of K4169 alloy were obtained by physical simulation,and the elastic-plastic model was deduced.Pro CAST was used to predict the size deviation of characteristic castings.Based on the experimental data,the predicted value of the size deviation of the elastic-plastic model was highly consistent with the actual value.3.The casting temperature and shell preheating temperature of investment casting characteristic castings were optimized by using mode FORNTIER software.The homogeneous Latin hypercube is stratified and randomly scattered.The response surface model of Pro CAST size deviation results is built by KR algorithm,and optimized by MOGA-II algorithm.Finally,MCDM is used to iterate.The data of optimization group and iteration group are less than the original value,which strongly illustrates the feasibility of the optimization process.4.The idea of high flux experimental design was introduced to reproduce the two solidification parameters of temperature gradient and solidification rate in the actual casting process.The relationship between solidification parameters and microstructural growth scale was studied by fitting regression analysis:?₁=0.2445G^-0.46V^-0.20;?₂=103.3832(GV)^-0.44.At the same time,it is also discussed that the permeability ratio of?₁/?₂ in solid-liquid region is not a constant,but a fluctuation value in the range of 1.57-3.58.The response behavior of secondary dendrite spacing is more sensitive to the change of solidification parameters than primary dendrite spacing.