Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was...Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was investigated.Steel samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,respectively.Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated sample.Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample.The electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance spectroscopy.As a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated sample.The impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.展开更多
文摘Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was investigated.Steel samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,respectively.Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated sample.Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample.The electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance spectroscopy.As a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated sample.The impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.
