Study On The Low Cycle Fatigue Properties Of Strain-Strengthen Austenitic Stainless Steel 022Cr17Ni12Mo2

The paper is supported by National Science and Technology Ministry,"Eleventh Five-Year","863"key project in the areas of advanced manufacturing technology,"The design, manufacture and maintenance of significant pressure equipment under extreme conditions"(2009AA044801). Based on referring to a large number of literatures and standards, through experimental study and theoretical analysis, this paper has studied the effect of prior deformation amount and deformation rate on the mechanical properties for strain-strengthening austenitic stainless steel 022Cr17Ni12Mo2,and explained the strengthen mechanism from the microscopic view; the effect of strain-strengthening on the low cycle fatigue properties for materials, the cycle stress response behavior and crack propagation mode have been depicted; the common life prediction models have been analyzed.(1)The strength index increases substantially and plasticity toughness as the deformation increases, the mechanical properties of strengthen state materials was not sensitive to deformation rate(the strain rate was at the range of 10-4~10-2s-1); Based on referring to domestic and abroad standard, deformation amount 4%,8% have been selected firstly. Twinning induced strength has been taken place.(2)Deformation martensite has not been discovered through examining the microstructure and phase composition of strengthen state samples; As deformation amount increases, the amount of deformation twin increases. It can be inferred that the strength has been improved by strain-strengthening due to the generation of deformation twin.(3)In general, Strain-strengthening austenitic stainless steel 022Cr17Ni12Mo2 exhibited lower total strain fatigue life; The effect of pre-strain on the fatigue behavior depends on the nature of the pre-strain. Tensile pre-strain result in reductions in the fatigue life throughout all of the fatigue range; The crack propagation model of solution-treatment and prior strain-strengthening samples was mostly transgranular.(4)Solution-treatment and prior strain-strengthening samples showed initial hardening in the first three cycles and then softening,reached a saturation response, except at a amplitude of 0.25% in a 4% prior strain-strengthening samples and at a amplitude of 0.25%,0.5% in the prior strain-strengthening 8% samples exhibited gradual softening from the beginning until the peak stress decreased rapidly.(5) The fatigue life of 4%PSS samples could be predicted by Manson-Coffin equation and the scattered belt was only 1.5 times ; the low cycle fatigue life of strain-strengthening austenitic stainless steel could be predicted accurately three parameter power function and three parameter strain energy function.