Abnormal Grain Growth Induced by Stress During An-nealing of Industrial Pure Titanium TA1
The influence of stress on the recrystallization process of pure titanium was investigated.Bending stress was applied during the annealing process of a pure titanium plate to observe the recrystallization process under tensile and compressive stresses on one section.Industrial pure titanium TA1 rolled plates with different deformation levels of 20％,40％,and 60％were prepared.These samples were then subjected to a temperature of 600 ℃ and a stress of 30 MPa for 10 min.It is found that in the samples with 20％and 40％deformation levels,only a few recrystallized grains are observed.Additionally,the average grain size in the region under stress becomes larger than that in the region without stress.To further investigate the grain growth,the rolled sheet with 40％deformation level was kept at 600 ℃ and 30 MPa for 60 and 120 min.It is observed that the abnormal growth of grains in the tensile stress area continues until the critical size is reached,after which they stop growing.The increased grain growth during recrystallization can be attributed to the stress-promoting dislocation adjustment.The grains with favorable conditions tend to grow abnormally along the direction of the applied stress.However,the high density of residual dislocations within the titanium plate results in a reduction in the driving force for grain growth,leading to the existence of critical size.These findings provide an explanation for different recrystallization behavior observed in titanium under tensile and compressive stresses.
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