Microflow Parameters of High-Strength Stainless Steel and Their Relationship with Mechanical Properties

Determination of material mechanical properties is always important and mandatory when assessing the design performance of a structure. Existing methods and standards require correspondence to norms and conditions during preparation, manufacture and testing of samples, making determination of mechanical characteristics labor consuming. Besides, the applied National and industry standards GOSTs, OSTs and methods predetermine the use of metal-intensive samples being as a rule selected with discontinuity violation, and, in the case of a process allowance, the mechanical characteristics imply a degree of certainty. Due to the development of the crystalline lattice defect theory, plastic strain and fracture are described by a physically justified analysis of the processes taking place in the material. A reliable method to determine the microflow parameters on miniature samples under compression has been developed and successfully applied for assessment and prediction of material mechanical properties. The method is based on local stress relaxation of a specimen of the steel under study. The advantage of this method is a certain physical interpretation of the parameters related to changes in material microflow mechanisms. In order to introduce the above-mentioned method into the experimental practice, a comparison of mechanical properties with microflow parameters was carried out using the example of industrial high-strength steel after hardening. The microflow parameters for steel grade 08X15N5D2T and their variation with respect to the aging temperature (Tc) are obtained. The parameters ( and s″), interpreted as the elastic strength and yield limit, respectively, increase in the range of aging temperatures: the release of a dispersed strengthening epsilon phase (e). When comparing the obtained parameters with the existing characteristics of the steel under study, it was found that there is a correlation between the microflow parameters and the yield limit. The plotted relations s″ = f(Tc), repeat the pattern of change in the yield limit curve s0,2 = f(Tc) regardless of the steel initial state.