Effect Of Quenching And Partitioning On Microstructure And Properties Of 301 Austenite Stainless Steel

Metastable austenite stainless steels?MASSs?with a wide range of application of transportation,architecture and electronic component exhibit austenite after solution and quenching to ambient temperature and then produce martensite after cold deformation or supercooling.MASSs are often considered strengthening by cold deformation to trigger strain-induced martensite transformation,which restrict their development and application in a certain extent due to complex treatment,higher costing and markedly lower content of austenite that degrades corrosion resistance and formability of MASSs.We study here that effect of quenching and partitioning treatment on microstructure and properties of MASSs to enhancing the strength and preserving their ductility and find the relationship of Q-P treatment,microstructure and properties,thereby offering theoretical foundation for optimizing the processing technology of MASSs.We research here that the effect of quenching and partitioning treatment on microstructure and properties of 301 MASSs.The microstructure is observed and analyzed by optical microscope,scanning electron microscope,transmission electron microscope,X-ray diffraction and ferrite magnetometer;the mechanical property is measured through tensile test,microhardness test and fracture morphology observation;and the corrosion property is tested by dynamic polarization measurement and electrochemical impedance spectroscopy.The main conclusions are as follow:?1?The microstructure of as-received hot-rolled sample is comprised of austenite and some impurities,and massive lath martensites containing high-density dislocation appear after quenching to deep-cryogenic temperature?-180??.When partitioning at400-500?,martensite content is degraded,the content and stability of austenite is elevated and some dispersive nanoscale M₂₃C₆ carbide ande-carbide are exhibited on the substrate.The crystallographic orientation between martensite and austenite after quenching and partitioning is in accordance with K-S relationship,which is?111?_A//?011?_M,[011]_A//[111]_M.?2?Compared with hot-rolled sample,the yield strength,ultimate strength and micro-hardness is significantly enhanced 146.27 MPa,166.67 MPa and 36.9 HV through quenching to-180? exposed in liquid-nitrogen,while the elongation is reduced 11.07%due to the degradation of austenite.After partitioning at 450? exposed for 30 min,elongation is elevated 9.80%and yield strength is further enhanced 61.72 MPa due to higher stability of austenite and precipitation of nona-scale carbides,and ultimate strength and micro-hardness are slightly decreased.We found that the optimal mechanical properties are obtained after partitioning at 450? exposed for 30 min,and the yield strength,ultimate strength,elongation and micro-hardness are432.37 MPa,1212 MPa,44.28%and 193.16 HV,respectively.?3?The self-corrosion current density in electrodynamic polarization curve and the capacitive reactance radius in electrochemical impedance spectroscopy of samples of hot-rolling,quenching and partitioning are successively enhanced,meaning the optimal corrosion resistance is obtained in partitioning state.It is found by the research of corrosion behavior in vary solutions that the corrosion resistance of 301 MASSs is significantly deterioated in acid medium,but has better corrosion resistance of alkali-corrosion than acid-corrosion.