A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and ...A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and mechanical properties of components.In order to analyze the forming process of the basin-like depression defect,a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis method.Subsequently,a series of parameters loading path schemes for force and current were designed by varying the initial value,peak value and value level,and their effects on basin-like depression and mixed grain structure were simulated and uncovered.It is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet,thus exerting the basin-like depression.Simulation results also indicate that these defects can be optimized through the parameter coordination between force and current.Finally,the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.展开更多
The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes...The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.展开更多
基金support from the National Natural Science Foundation of China(No.52175287)Open Fund of State Key Laboratory of Materials Processing and Die&Mould Technology,China(No.P2020-001).
文摘A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and mechanical properties of components.In order to analyze the forming process of the basin-like depression defect,a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis method.Subsequently,a series of parameters loading path schemes for force and current were designed by varying the initial value,peak value and value level,and their effects on basin-like depression and mixed grain structure were simulated and uncovered.It is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet,thus exerting the basin-like depression.Simulation results also indicate that these defects can be optimized through the parameter coordination between force and current.Finally,the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.
基金This project is financially supported by the Natural Science Foundation (No. E5305293) of South China University of Technology.
文摘The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.