Effect of alloying elements V and Cu on microstructure and properties of Cu-bearing steels
Three kinds of Cu-bearing high strength steels,namely 0V1Cu steel,0.15V1Cu steel and 0.15V4Cu steel,respectively,were designed to study the effect of V and Cu elements on microstructure and properties.The phase transformation,microstructure and microhardness of experimental steels were investigated using various microstructure characterization techniques,such as LOM,SEM,TEM,along with thermodynamic and kinetic calculations.The experimental results revealed that the Ac1 temperat-ure of the three steels was within the range of 673～675 ℃.When 1％Cu was added and V increased from 0 to 0.15％,the Ac3 temperature increased from 769 ℃ to 775 ℃,and with Cu increased from 1％to 4％in steel including 0.15％V,the Ac3 temperature decreased from 775 ℃ to 757 ℃.After hot rolling,the microstructures of 0V1Cu steel and 0.15V1Cu steel were identified as granular bainite,while 0.15V4Cu steel exhibited a microstructure consisting of martensite and a small fraction of bainite.Lath martensite was obtained in all the three steels after austenitization at 1100 ℃ for 5 min,followed by quenching in water.The addition of V and Cu lead to an increase in the microhardness of the Cu-bearing steels,with the highest microhardness(HV)of 597±7 observed in 0.15V4Cu steel,which was 44 and 11 higher than 0V1Cu steel and 0.15V1Cu steel,respectively.These findings demonstrated that the microstructure and mechanical properties of the studied steels could be adjusted over a wide range by varying the amounts of V and Cu,providing valuable insights for the design of Cu-bearing steels with excellent overall performance.
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