INVESTIGATION OF COLD ROLLING PARAMETERS OF ULTRAFINE GRAINED TITANIUM
The objective of the work was achieving fatigue and strength properties of commercial titanium VT1-0 by hardening in cold working process. Cold rolling is a common method of hardening of materials and alloys. The interest to cold rolling as a deformation scheme is due to the fact that rolling process is fully explored and widely used in practice. Ultra-fine grained blanks (diameter 40 mm and above) received by severe plastic deformation process were rolled on CNC (computerized numerical control) cluster mill. Standard cylindrical samples for determining tensile and compression properties and fatigue-strength test were made by rolling. Experimental data show an increase of strength characteristics of nanostructural titanium as a result of cold rolling. Samples were also investigated with the CNC-2 plastometer by the method developed by the Machines and Technology of Material Deformation Processes Department of the South Ural State University. After plastometric research the samples were tested to determine deformation resistance, tensile strength and Brinell hardness. Divisibility of deformation increases yield point for all stressing degrees. Increase of σ0,2 and hardness is a witness of grain refinement. The plasticity research of commercial titanium under divisional stress shows that plasticity of titanium increases with increasing number of stress degrees. Tests showed no significant effect of tempering at intermediate stress degrees on tensile strength and hardness of titanium.