Effect of Strain Rates and Pre-strains at Room Temperature on the Mechanical Properties of Austenitic Stainless Steel

This investigation has been carried out to make clear the effect of strain rates and pre-strains on the mechanical properties and the phase transformation of Austenitic stainless steel at diverse temperatures. The formation of martensite is examined by X-ray diffraction, specific gravity and permeability measurements and transmission electron microscopy.The main results obtained are as follows:(1) The tensile strength at room temperature which increases not only at high strain rate but also at low strain rate, shows the lowest value at the strain rate ε=4×10−2. But the flow stress increases linealy with strain rate. The reduction in area decreases with increase in strain rate.(2) The mechanical properties at low temperatures are influenced by chemical compositions and show unique behaviors. Chemical compositions and strain rates give a remarkable effect on the amount of martensite formed with plastic deformation. The degree of martensite formation decreases with increase in strain rate.(3) Stainless steel pre-strained at room temperature shows the “plateau” similar to Lüders band in the stress-strain curves at −196°C. The length of the plateau depends on the amount of the prestrain at room temperature.