S32750双相不锈钢相界与晶界特征对其力学性能和耐蚀性能的影响EI北大核心CSCD

通过固溶处理获得不同初始组织状态的S32750双相不锈钢样品,然后进行厚度压下量80%的冷轧变形和1050℃的退火处理,采用SEM-EBSD和XRD技术研究合金相界与晶界特征以及相组成分布情况,并利用拉伸实验、纳米压痕和双环电化学动电位再活化法(DL-EPR)分析不同初始状态样品的组织对力学性能与耐晶间腐蚀性能的影响规律。结果表明:高温固溶处理的合金样品经冷轧退火后晶粒细小均匀,两相分布接近1∶1,且相界占内界面(晶界+相界)比例较高,同相晶粒团簇程度最低,表现出优异的综合力学性能。合金样品经敏化处理后,σ相易沿α相晶界析出,高温固溶并经轧制退火后的样品中,由于α晶界比例较少且满足K-S取向关系的相界比例较高则又表现出良好的晶间腐蚀抗力。因此,通过适当的工艺来调控合金的相界与晶界分布可以实现材料强度和晶间腐蚀抗力的同步改善。

Effect of phase boundary and grain boundary characteristics on mechanical properties and corrosion resistance of S32750 duplex stainless steel

S32750 duplex stainless steel samples with different initial microstructures obtained by solid solution heat treatment(SHT)were cold rolled with the thickness reduction of 80%and subsequently annealed at 1050℃.The distribution of phase boundary and grain boundary character for the as-processed samples was investigated by SEM-EBSD and XRD techniques.Furthermore,the effect of microstructure on mechanical properties and intergranular corrosion resistance was analyzed by means of tensile testing,nano-indentation and double loop electrochemical potential reactivation(DL-EPR)method.The results show that the fine-grained microstructure with the areal ratio ofαtoγabout 1,the highest fraction of phase boundaries out of the total interfaces(grain boundaries+phase boundaries),and the least grain clustering within the respectiveαandγphases was obtained in the sample previously treated by high temperature SHT and subsequent cold rolling and annealing.As a result,the sample exhibits excellent mechanical properties.After the cold-rolled and annealed samples are sensitized at 750℃for 4 h,theσphase precipitates readily along theαgrain boundary.The sample previously treated by high temperature SHT and subsequent cold rolling and annealing also possess better intergranular corrosion resistance due to the relatively small amount ofαgrain boundary and high population of phase boundaries meeting K-S orientation relationship betweenαandγ.Therefore,the strength and intergranular corrosion resistance might be improved simultaneously by controlling and designing interface character distribution via appropriate thermal mechanical treatment in duplex stainless steel.