Relationship between the structure and physical-mechanical properties of U8A steel subjected to cold plastic deformation by hydrostatic extrusion

The structure and physical-mechanical properties of U8A high-carbon steel subjected to cold plastic deformation by hydrostatic extrusion have been investigated in a wide range of strain extents. Cold plastic deformation by hydrostatic extrusion has been shown to lead to the dispersion of the structure of U8A high-carbon steel. As the degree of true deformation increases, the ultimate strength and conventional yield limit of U8A steel monotonically grow by 2 and 3.6 times, respectively. Such parameters as coercive force, the number of jumps in magnetic Barkhausen noises, maximum magnetic permeability, residual induction, and the speed of elastic waves are more sensitive to changes in the dislocation density than in the dispersion of the grain and subgrain structure of extruded U8A steel. It has been established that at least two informative testing parameters are needed for nondestructive evaluation of the level of strength properties in extruded U8A steel. Those are coercive force (or maximum magnetic permeability, residual induction, the number of Barkhausen jumps, the speed of elastic waves) for a true deformation of up to 1.62 and the root-mean-square voltage of magnetic Barkhausen noises for true deformations above 1.62.