Plastic deformation and damage behaviors of Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel under uniaxial tension and compression

Abstract

Uniaxial tensile and compressive deformation behaviors of Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel were investigated at different strain rates. It is found that, with increasing strain rate, the yield strength of the steel increases either under tension or compressio n, while the ultimate tensile strength and the total elongation decrease under tension. The plastic deformation behavior prior to necking under uniaxial tension at different strain rates can be well described by the modified Ludwik relation. Under tensile deformation at the low strain rate of 10 -4 s -1, microcracks prefer to initiate around the Al 2 O3 particles in the steel, whereas cracks nucleate at grain boundaries or along slip bands at the high strain rate of 10 -2 s -1 . Compressive deformation behavior of the steel is not so sensitive to the strain rate. The surface fluctuation is more serious under compressive deformation rather than tensile deformation. The tensile plastic deformation is mainly governed by the formation of planar slip bands and deformation twins, and deformation by twinning becomes more prominent with increasing strain rate, while dislocation slip featured by planar slip bands, dislocation bands and twin-like bands basically controls the compressive plastic deformation, and deformation twins are rarely formed.