Strain Rate Dependence of Strain-Induced Martensitic Formation and Tensile Ductility in SUS304 Stainless Steel

Abstract

We investigated martensitic (α') phase distribution in tensile-deformed SUS304 stainless steel by X-ray diffraction examination at the strain rate from 7.1×10^-4 /s to 9×10² /s. The elongation decreased with increasing the strain rate at the strain rate below 7.1×10^-1 /s and it was almost constant beyond the strain rate. On the other hand, the reduction of area was almost constant at the strain rate below 7.1×10^-1 /s and it gradually decreased with increasing the strain rate. The amount of α' phase (V_α') tended to decrease with increasing the strain rate, and it increased with decreasing the distance from a fractured face. The true strain is calculated from the cross-sectional reduction. The relationship between the true strain and V_α' is described using the Angel's equation, and the α' phase distribution is predicted from the true strain distribution. The V_α' of the total specimen (V_α',tot) and the V_α' around the fractured face (V_α',frac) are calculated from the α' phase distribution. The strain rate dependence of elongation correspond with the strain rate dependence of V_α',tot. The reduction of area tend to decrease with increasing strain rate above 7.1×10^-1 /s when the decrease in the V_α',frac was observed.