Effect Of Cold Deformation And Phase Reversion Methods On Strength-Plasticity And Corrosion Resistance Of Austenitic Stainless Steel

Austenitic stainless steel has a high plasticity and corrosion resistance and is widely used in the automotive,medical,chemical,nuclear power,and other industries.Austenitic stainless steel,on the other hand,is made up of coarse face-centered cubic grains,resulting in low yield strength and limited application as structural parts.Deformation strengthening and grain refinement strengthening are both effective methods for increasing austenitic stainless steel yield strength.The procedure is simple and straightforward,and the impact on plasticity and corrosion resistance is minimal.However,the effect of deformation strengthening and grain refinement strengthening on plasticity and corrosion resistance,as well as the underlying mechanism,remain unknown,necessitating additional research.In this study,the Fe-18Cr-8Ni austenitic stainless steel was used as the received material,and the as-received sample was cold-rolled at room temperature with the thickness reduced from 10% to 90% to obtain cold-rolled samples(CR).The ultrafine grain/fine grain(UFG/FG)structure was obtained by annealing the 90 % CR sample and the 60 % CR sample at 850 °C and 900 °C for 300 s and 180 s,respectively.The following are the experimental findings:(1)The yield strength and tensile strength of CR samples gradually increase as the CR reduction increases,while the plasticity decreases.10% CR samples have good strength plasticity matching,with yield strength and elongation of 550 MPa and 43%,respectively.It is due to the coexistence of various deformation mechanisms in the tensile process(including dislocation slip,deformation twin,and deformation martensite).The strain hardening and fracture behavior exhibit three-stage strain hardening curve and dimple characteristics.(2)The phase reversed austenitic stainless steels exhibited varying grain sizes.The yield strength and tensile strength decreased as grain size increased,while plasticity increased.By annealing at 850 °C,UFG/FG austenitic stainless steel can be obtained,with yield strength and elongation of 550 MPa and 73 %,respectively.When compared to 10% CR samples,in addition to having a three-stage strain hardening curve and a dimple,UFG/FG samples exhibited larger strain range of stage A and stage B and better plasticity(enhanced 30%),which is attributed to a large number of deformation twins,a small amount of dislocation slip,and the formation of deformed martensite.(3)The cold rolling and reverse transformation annealing process not only increased the yield strength of austenitic stainless steel,but also improved the pitting corrosion resistance under the action of chloride ions.This is because the reduction of grain size to overcome the formation of martensite during deformation strengthening and grain refinement strengthening reduced frequency of metastable pits to increase the difficulty of pitting corrosion.(4)Austenitic stainless steel’s intergranular corrosion resistance is improved by cold rolling deformation and phase reversion annealing.The reactivation rate of the asreceived sample is 45.34%.The chromium carbide precipitated from the cold rolling after sensitization is evenly distributed in the grain boundary and slip band,and the reactivation rate is reduced to 33.60 %.The chromium carbide of the UFG/FG sample precipitates to the grain boundary,annealing twins,and other crystal defects,and the ultrafine grain of the UFG/FG sample further makes the chromium carbide and chromium poor area evenly distributed,which greatly reduces the intergranular corrosion sensitivity and obtains excellent intergranular corrosion resistance(0.39%).