Study On The Thermal Deformation Behavior Of Nickel-based Superalloy 718Plus

The 718Plus superalloy is a kind of nickel-based superalloy developed by ATI Allvac company in the United States.With excellent mechanical performance,thermal workability and welding property as IN718 superalloy,as well as obvious high-temperature resistance and thermal stability as Waspaloy superalloy,the alloy is considered as one of the important candidate materials for manufacturing aeroengine parts.Based on a series of isothermal compression tests of 718Plus superalloy under different deformation conditions,the high temperature deformation behavior of 718Plus superalloy was investigated,the hot working process was simulated,and the influence of deformation parameters on microstructural evolution was analyzed,which provides reasonable processing parameter and theoretical guidance for the practical production,and further promotes the industrial application.The main research results are as follows:The flow stress curves of 718Plus superalloy present obvious dynamic recrystallization characteristics.The variation of flow stress with strain mainly results from the competition between work hardening caused by dislocation proliferation and pile-up and flow softening induced by dynamic recovery and dynamic recrystallization.The flow stress of 718Plus alloy decreases with the decrease of strain rate or increase of deformation temperature.The modified Arrhenius constitutive model of 718Plus superalloy considering the compensation of strain was established with AARE of 4.99%and R value of 0.995,which presents good agreement with experimental values.Based on the processing map,the optimum processing region was confirmed as deformation temperatures of980⁹85?with strain rates of 0.001⁰.003s^-1 and deformation temperatures of1060¹100?with strain rate of 0.01s^-1.Besides,the strain rate can be appropriately increased when deformed slightly above 1100?,and the deformation temperature can be reduced appropriately when deformed below 0.01s^-1.Microstructure characterization showed that the dynamic recrystallized grains of718Plus superalloy nucleate and grow up along the grain boundary and twin boundary of original grains during hot processing,presenting obvious"necklace"structure.With elevated deformation temperature or dropped strain rate,both the volume fraction and grain size of dynamic recrystallization increase.Taking?phase dissolution temperature as the border temperature,the critical strain model,kinetics model and grain size model of dynamic recrystallization were established for 718Plus superalloy within deformation temperatures of 1020¹140?and strain rates of 0.001¹s^-1.The hot working process of 718Plus superalloy was simulated through Deform-3D finite element simulation software.Results show that the deformation temperature and strain rate have little influence on the distribution of equivalent strain in the workpiece.Finally,the accuracy of dynamic recrystallization kinetic model was verified by comparing the simulation results with experimental data.