Effect Of Stress On Recrystallization Behavior Of Industrial Pure Titanium TA1

Grain boundaries,as surface defects in crystals,have an important influence on the transformation processes that occur in crystalline materials.One of which is the recrystallisation process activated by plastic deformation of metals at high temperatures.Recrystallisation has been extensively studied and insights accumulated,but few studies have been reported relating to the effect of applied stress on recrystallisation behaviour.To investigate the effect of stress on recrystallization,this paper uses bending experiments to investigate the asymmetry of recrystallization behavior under tensile and compressive stresses,and designs recrystallization experiments under two different conditions:annealing experiments after plastic strain in three-point bending and recrystallization experiments for rolled plates under constant elastic stresses,using industrial pure titanium TA1 plates as raw materials.Samples with different deformation methods and deformation amounts were prepared by three-point bending,hot rolling and cold rolling processes for systematic study.The samples were characterized by metallographic microscopy and electron backscatter diffraction techniques for microstructure,and the recrystallization was quantified by microhardness,and the results were analyzed by AZTEC data analysis software to reveal the influence law of stress on recrystallization.The influences of plastic deformation on recrystallization behavior under different stress states were investigated by sampling in the RD and TD directions of fully annealed rolled plate and annealing at different time after three-point bending experiment.The polygonization of samples under compressive stress was obvious,resulting in the increase of the subgrain boundary ratio of RD sample from 0.288 to0.31,the increase of the subgrain boundary ratio of TD sample from 0.428 to 0.5,and the decrease to 0.206 and 0.26 in the subsequent annealing process,respectively.The start time of recrystallization did not change significantly.Almost all recrystallized grains appear after 2 h annealing.Compressive deformation results in obvious recovery,while tensile deformation does not.The sample was annealed in pure bending by applying an external load,and the recrystallization behavior in the elastic tensile/compressive stress state was analyzed.During the recovery phase,the stress will increase the grain size,the average grain size in the elastic compressive stress region was 34.47μm,the average grain size in the elastic tensile stress state was 39.33μm,and the average grain size in the intermediate unstressed region was 32.5μm,all of which were larger than the grain size in the original tissue of 27.925μm.During the annealing process of the 40%deformation sample,some grains under the elastic tensile stress occurred abnormal growth while the internal fault density is still relatively high.The dislocation density in the annealed10 min sample was close to 10¹⁵/m²,the dislocation density in the annealed 1 h sample decreased to 10¹⁴/m².However,the dislocation density in adjacent grains is still high,resulting in abnormal grain growth.and the dislocation density in the annealed 2 h sample almost did not decrease,and finally was swallowed by the recrystallized grains and disappeared.The application of loads also affects the size of fully recrystallized grains.The average grain size was 24.0622μm at 24 MPa stress,which increased to24.974μm after the stress was increased to 38 MPa and to 25.1082μm after the stress level was increased to 49 MPa。...