120°模具室温ECAP制备工业纯钛的热压缩变形行为

Hot Compression Deformation Behavior of as-ECAPed CP-Ti at Room Temperature with 120° Die

摘要:

在Gleeble-1500热模拟机上对室温120°模具等径弯曲通道变形(ECAP)制备的平均晶粒尺寸为200 nm的工业纯钛(CP-Ti)进行等温变速压缩实验，研究超细晶(UFG)工业纯钛在变形温度为298~673 K和应变速率为10-3~100 s-1条件下的流变行为。利用透射电子显微镜分析超细晶工业纯钛在不同变形条件下的组织演化规律。结果表明：流变应力在变形初期随应变的增加而增大，出现峰值后逐渐趋于平稳；峰值应力随温度的升高而减小，随应变速率的增大而增大；随变形温度的升高和应变速率的降低，应变速率敏感性指数m增加，晶粒粗化，亚晶尺寸增大，再结晶晶粒数量逐渐增加；超细晶工业纯钛热压缩变形的主要软化机制随变形温度的升高和应变速率的降低由动态回复逐步转变为动态再结晶

Abstract:

Hot compression deformation behavior of Ultrafine-grained (UFG) commercially pure (CP) Ti with the average grain size of 200 nm was studied by thermal simulation test at the deformation temperature of 298-673 K and the strain rate of 10-3-100 s-1 on the Gleeble-1500 thermal-mechanical simulator. UFG CP-Ti was produced by ECAP up to 8 passes with a die of Φ=120° using route Bc at room temperature. The microstructural evolution of UFG CP-Ti was investigated by transmission electron microscopy. The results show that the flow stress increases with increasing of strain and tends to be constant after a peak value. The peak stress increases with increasing of strain rate and decreases with increasing of deformation temperature. Strain rate sensitivity value m of the UFG CP-Ti is found to increase with increasing of temperature and decreasing of strain rate. And the grains in the deformed samples are coarsened and the size of subgrains increases; the number of fine grains in grain boundaries also increases, indicating that the main softening mechanism of the alloy during hot compression deformation is attributed to the transformation from dynamic recovery to dynamic recrystallization