Effect of Microstructure Variation on Differential Hardening Behavior of Steel Sheets under Biaxial Tensile State

Effect of Microstructure on Surface Roughening in Stretch Forming of Steel Sheets

“…For details of the experimental apparatus, refer to our previous reports. 35,39) Biaxial tensile tests were conducted at a cross head speed of 2.5 μm/s. The equivalent strain was evaluated from the changes of length between the crystal triple points in RD and TD.…”

“…Experimental apparatus for biaxial tensile test with SEM-EBSD analysis. 35,39) (Online version in color.) the authors (see above 2.3).…”

“…In the IPF map at the equivalent strain of 0.13, the distribution of crystal orientations is also seen within the grains as is seen in material D. Material C has the developed texture of ND(111) before deformation, and the texture develops more with deformation. 39) Compared with material D, the area where crystal grains with ND(001) orientation exist is small. This result also agrees with the intermittent observation of microstructures shown in Fig.…”

Influence of Strain Ratio on Surface Roughening in Biaxial Stretching of IF Steel Sheets

“…Microscopic Biaxial Tension Test In order to precisely examine the relationship between the deformation mode and the development of surface roughness, changes of surface conditions including microstructure and texture were observed continuously using a biaxial tension test system equipped inside a vacuum chamber of SEM (details of the experimental apparatus are given in our previous reports 22,23) ). Two types of tests, i.e., equi-biaxial tension (β = 1.0) and plane-strain tension (β = 0.0) were carried out by controlling the stroke motions in two directions.…”

“…In our previous study, therefore, surface roughening and the change of microstructure of IF steel sheets during biaxial tension deformation were examined in detail using two types of tests. One was a macroscopic Marciniak type test 21) and the other was a microscopic biaxial tensile test developed by the authors, 22,23) which enables in-situ continuous observations of sheet surface during biaxial deformation, using a scanning electron microscope/electron backscattered diffraction pattern (SEM/EBSD) method. The results showed that not only the grain size but also the texture of the sheet has a great influence on surface roughening, and that surface roughening became large for sheets which had a large number of crystal grains with orientations in the vicinity of normal direction (ND) (001), due to inhomogeneous deformation derived from their lower deformation resistance.…”