Study On Hot Deformation Behavior Of 17-4PH Stainless Steel

As an important structural material for nuclear reactors,17-4PH stainless steel is widely used by western countriesin chemical and power plants,such as light water reactors(LWR)and pressurized water reactor(PWR)due to its good mechanical property,hightemperature performance,simple heat treatment process and good corrosion resistance.So far the research on hot deformation behavior of 17-4PH stainless steel is rarely reported,and its hot work characteristics are not thoroughly understood.High temperature plastic periment was taken on Gleeble-3500 thermal-mechanical simulator by isothermal axial compression.The experimental datas gotten from Gleeble-3500 thermal simulator related to the deformation behaviors,evolition behaviors of the microstructure and hot process map for 17-4PH stainless steel.The restoration mechanisms of the alloy at temperatures have been studied with the aids of OM?TEM.Explore the quantitative relationship between flow stress,strain rate and deformation temperature and dynamic softening mechanism.and the hot process map was drawn based on dynamic materials model.Takinganalysis of hot process map to explore the reasonable hot working area of 17-4PH stainless steel.The main conclusions are as follows:(1)The flow stress of 17-4PH stainless steel increased with the increasing of strain rates and decrease of strain temperature,and the former indicated 17-4PH stainless steel is positive strain rate sensitive material.When deformation temperature was 1000?,the peak stress increased from 113.42 MPa to 232.04 MPa with the strain rate increasingfrom 0.01s-1 to 5s-1.(2)Only in a few experimental conditions(T=1100?? e·=0.01s-1and T=1050??e·=0.01s-1)could find the obvious characteristics of peak stress.The dynamic recrystallization softening mechanism plays the leading role in these condition.At the same time,when the temperature was less than 1000? and the strain rate was less than 5s-1,the dynamic recrystallization mechanism occupiy the leading rolein most conditions.(3)When the strain rate was constant,the microstructure of hot compression sample forms had significant changes at different deformationtemperatures.when the strain rate rised,17-4PH stainless steel's work hardening effected appearded more,grains was elongated along the rhe ological direction.When the temperature rised,the degree of recrystallization becomed larger,distortion degree reduced,the volume fraction of dynamic recrystallization grain size increased accordingly.(4)A peak stress constitutive equation was constituted by calculation,based on Arrhenius hyperbolic sine function: [ ]·5.955116456473The error of peak stressbetween the model and the actual measurement is 5.62%.(5)The critical strain model was constituted with the theory of dynamic recrystallization: 0.1354X10(47479.04 / 8.314)4.95pe eexp T-·(28)0.8c pe(28)e(6)The hot process map of 17-4PH stainless steel was established based on dynamic materials model.The early deformation of 17-4PH stainless steel was prone to instability,It has no significant difference of the hot process map between strain 0.3 and 0.6,and the power dissipation efficiency decreases rapidly in flow instability region.when the strain was 0.1,the power dissipation efficiency is 0.16 and less than the peak.so as the other strain(e(28)0.3,0.6).(7)When the strain is 0.6,it is suitable for hot work in the processing areaof T=1062?~1100? and e·? 0.023.The inadaptationscope for deformation was T=950?-1028??·e =0.27s-1-5s-1.