Effect of Drawing Strain on Development of Martensitic Transformation and Mechanical Properties in AISI 304L Stainless Steel Wire

摘要

AISI 304L stainless steel wires are cold drawn to different strains for examining the effect of plastic deformation on the mechanical properties change, the microstructural evolution, and martensitic transformation. Microstructures of drawn wires are characterized using optical microscopy, X-ray diffraction and electron backscatter diffraction (EBSD) techniques. It is shown that deformed structure consists of austenite, alpha-martensite, and epsilon-martensite. The ultimate strength of wires drawn to strains of 0.56, 1.13, and 1.7 are found to be equal to to 1028, 1492, and 1743 MPa, respectively, from intial value of 735 MPa. These strengths are correspond to the strain induced martensite of 34, 62, and 100%. Also, it is shown that elastic modulus of wires are changed due to the strain induced transformation during cold drawing. For accessing the strain distribution during wire drawing, FEM simulations are carried out according to the experimental investigations. By help of simulation results and applying different criteria, it is shown that regions near the wire surface are suitable area for initiation of strain induced martensite. Moreover, microstructural observations and hardness measurements reveal that the amount of strain-induced martensite is higher just below the surface.