摘要
The fine grained dual phase （FG-DP） steel with ferrite grains of 2-4.5 μm and martensite islands smaller than 3 μm was obtained through the mechanism of deformation-enhanced ferrite transformation （DEFT）. Mechanical properties of the steel were tested at room temperature. The results indicated that with a similar volume fraction of martensite （about 20vol%）,FG-DP steel exhibited a superior combination of higher strength and more rapid strain hardening at low strains compared with the coarse-grained dual phase （CG-DP） steel obtained by critical annealing. The combination of higher strength,large elongation,and more rapid strain hardening of FG-DP steel can be attributed to the fine ferrite grain and finely dispersed martensite islands. In addition,the uniformly distributed martensite islands in FG-DP steel have smaller interspacing compared with that of CG-DP steel. So,at the initial plastic deformation stage,the plastic deformation of ferrite was restrained and more pronounced load was transferred from ferrite to martensite. The plastic deformation of martensite in FG-DP steel started earlier.
The fine grained dual phase （FG-DP） steel with ferrite grains of 2-4.5 μm and martensite islands smaller than 3 μm was obtained through the mechanism of deformation-enhanced ferrite transformation （DEFT）. Mechanical properties of the steel were tested at room temperature. The results indicated that with a similar volume fraction of martensite （about 20vol%）,FG-DP steel exhibited a superior combination of higher strength and more rapid strain hardening at low strains compared with the coarse-grained dual phase （CG-DP） steel obtained by critical annealing. The combination of higher strength,large elongation,and more rapid strain hardening of FG-DP steel can be attributed to the fine ferrite grain and finely dispersed martensite islands. In addition,the uniformly distributed martensite islands in FG-DP steel have smaller interspacing compared with that of CG-DP steel. So,at the initial plastic deformation stage,the plastic deformation of ferrite was restrained and more pronounced load was transferred from ferrite to martensite. The plastic deformation of martensite in FG-DP steel started earlier.
基金
the Major State Basic Research and Development Program of China (No2004CB619102)
