Research On Microstructure And Properties Of 90W-7Ni-3Fe Tungsten Heavy Alloy By Liquid Phase Sintering

Tungsten heavy alloy,as a typical two-phase alloy,is the primary material for kinetic penetrators due to its high density,high strength,good plastic and other excellent performance.The penetrator is under coupling environment containing the temperature field and the stress-strain field from the launch,flight to the target penetration,so it's necessary to study the deformation and failure behavior of the tungsten alloy under the temperature field and stress-strain field.In this paper,the 90W-7Ni-3Fe tungsten heavy alloy by liquid phase sintering was used as the experimental material.The tensile and compressive properties of tungsten alloy were studied at room temperature and high temperature.The mechanism of fracture and plastic deformation were analyzed throuth SEM of failure and microstructure.The dynamic properties and microstructure of tungsten alloy at room temperature were also discussed.In this paper,the basic physical and mechanical parameters of as-sintered 90 W alloy were measured and characterized and the mechanical properties and microstructure of 90 W alloy at room temperature were analyzed.The study found that tensile properties of 90 W alloy at room temperature varied with increasing strain rate: tensile strength and cleavage fracture of tungsten increased,plasticity and ductile tearing decreased.The plastic deformation behavior of tungsten heavy alloy is a coordination between tungsten particle and matrix and the alloy has the highest plasticity at 10-3s-1.The yield strength of 90 W alloy increases remarkably at high speed strain rate with respect to quasi-static compression.The tensile test of 90 W alloy at 473-1473 K showed that the strain-rate had no significant influence on the mechanical properties at elevated temperature.The study found that the strength and the plasticity changed obviously of 90 W alloy at 673 and 1273 K.The strength decreased significantly at 473-673 K,then increased and came forth a platform till 1273 K,then decreased significantly.The alloy had the highest plasticity at 673 K,the plasticity decreased slowly till 1273 K and the alloy showed poor plasticity and tended to be steady above 1273 K.By scanning the fracture surface,it was found that the main fracture mode of 90 W was ductile tearing,and the intergranular fracture of W-W was rarely seen at 673 K.The results of compression of 90 W at 1073 K to 1473 K and 10-3s-1 to 10-1s-1 showed that the mechanical behavior of 90 W alloy was under the coupling effect of temperature and strain rate.The mechanical properties of 90 W alloy deteriorated significantly due to the abnormal growth of tungsten particles at 1473 K.Shear band with an angle of about 45° to the compression direction appeared at the corner of samples at 1073 K.Defects on phase interface appeared due to inconsistent deformation.In order to describe the plastic deformation behavior of 90 W alloy at elevated temperature,this paper established six constitutive equation based on JC model,modified JC model,Arrhenius model and modified ZA model.Constitutive equations on the reference of 293 K and 1073 K based on JC model and modified JC model were established respectively.The accuracy and prediction of each equation were quantitatively calculated by the correlation coefficient and the absolute average relative error.The constitutive equation based on Arrhenius model and modified ZA model had higher accuracy while constitutive equation based on JC or modified JC model had large error since the Arrhenius model and ZA model had a more comprehensive consideration of temperature,strain and strain rate coupling effect on flow stress.