Numerical Study On The Effect Of Powder Density And Temperature On The Densification Process Of Powder By Hot Isostatic Pressing

Hot isostatic pressing near final forming(HIP-NNS)technology is used to prepare complex metal parts,which has a broad application prospect in powder metallurgy industry.At present,HIP process design mainly relies on trial and error and subsequent iteration to correct to get ideal results.In view of the long test period and waste of resources,finite element simulation technology is a scientific and effective method to improve.The main purpose of this paper is to develop a numerical simulation method more suitable for the powder compaction mechanism of plasticity,elasticity,creep,to guide the experiment,and study the influence of powder density field,temperature field and stress field on the compaction process,provide an important basis for the optimization of powder HIP process,the accuracy of HIP prediction will reach a new height.The accuracy of finite element simulation largely depends on the choice of constitutive model.Compared with the densified metal forming,the densification process of metal powder has its special mechanical behavior.The density and volume of the powder change,and the powder undergoes plastic deformation,diffusion and creep.Mises yield criterion can not meet the requirements.In this paper,the coupled constitutive models of heat,elastoplasticity,creep and relative density change and the numerical integration algorithm were studied,and the constitutive models of heat,creep,plasticity and density were coupled into an integrated coupled constitutive model,and a thermally elastoplasticity-creep-relative density constitutive model was established.The user defined material subroutine(UMAT)was written in FORTRAN language,and the commercial finite element software ABAQUS was used to simulate the HIP process of SS316 L powder material and SS304 ladle sheath.The changes of powder density field,temperature field and stress field during HIP process were investigated.At the same time,the Drucker-Prayer/Cap model is studied.The customized UMAT constitutive model and Drucker-Prayer/Cap model are respectively used to simulate the densification of HIP process,and the analysis results are compared and analyzed to verify the applicability of the newly derived combined constitutive model.The results show that: The description of the forming law of metal powder under high temperature and high pressure by the self-defined constitutive model is consistent with the test,which verifies the efficiency of the model algorithm and the correctness of the calculation program.Moreover,compared with the Drucker-Prayer/Cap model,the self-defined constitutive model is more applicable in the powder HIP.It is proved that the model can reasonably predict the deformation behavior of metal powder under high temperature and high pressure.It also successfully explores the variation law of powder density field,temperature field and stress field during densification,which lays a solid foundation for the optimization of powder HIP process.