Estimation of Local Plastic Deformation in a Bulk of Polycrystalline Materials

The article deals with the local plastic deformation analysis after cold forming. The technology of drawing seamless steel tubes was used to obtain cold-formed samples. The tubes were manufactured by a Tinius Olsen 300ST tensile tester with a 6 ° and 12 ° die drawn without and with an inner mandrel. Based on orientation size recalculated by stereology and applying Monte Carlo method a mathematical conversion model was developed. Implemented model together with surface measurements and structure characteristics were used to get the orientation to the size of the deformation. Thus, the actual (logarithmic) deformations and local stresses were determined. Comparison of experimentally measured values of the actual local plastic deformation with the deformation calculated found on the model simulation in the Deform program defined the significance of the differences assessed by means of a statistical T-test. All differences in the values of the local plastic deformation with respect to the position were evaluated as statistically insignificant and therefore the difference between the experimental calculation and the simulation is random.

THE ROLE OF MASS-TRANSFER IN THE MATERIALS SURFACE LAYER STRUCTURING UNDER EXTREME HEATING

Possible causes of mass transfer acceleration of carbon atoms and alloying elements in the surface layers of steels and alloys under extreme heating, under pulsing laser irradiation in particular, are considered. The research shows that the anomaly accelerated mass transfer, including diffusion in particular, in steels and alloys under fast laser heating has a cooperative character and is a result of a simultaneous action of several processes of different physics. It is proved that the carbon atoms mass transfer parameters and alloying elements depend on the scale and the level of emerging tension, relaxation of which goes along with a local plastic deformation, and occurrence of increased number of linear defects in crystal structure. Experimental and theoretical studies have found that with the temperature of the laser heating lowered along the depth of the irradiated areas the mechanism of mass transfer will change as follows: atoms move in the fused spot area under the influence of Marangoni effect; a contact melting and liquid-phase diffusion occur at the boundaries with the solid matrix; Soret diffusion under the action of local plastic deformation also occur; atoms move along the irradiated zone in an atoms "drift" mechanism within the area of moving dislocations.