复合加工制备的超细晶工业纯钛室温蠕变行为研究

Investigation of creep behavior of ultra-fine grained CP-Ti processed by combined machining at room temprature

摘要:

工业纯钛TA1经等径弯曲通道变形(Equal channel angular pressing, ECAP)+冷轧(Cold Rolling, CR)+旋锻(Swaging)的方法制得晶粒尺寸约为120 nm的超细晶工业纯钛，通过单轴拉伸蠕变实验、透射电子显微镜（TEM）、扫描电子显微镜（SEM）等方法，研究室温下超细晶工业纯钛蠕变变形行为及机理。结果表明：在实验应力范围内，超细晶工业纯钛存在明显的室温蠕变现象；随加载应力的上升(640MPa~760MPa)，蠕变量增加，稳态蠕变速率增大(2.8×10-7s-1~1.5×10-4s-1)；在相同蠕变应力水平(0.8σs)下，超细晶工业纯钛稳态蠕变速率(2.8×10-7s-1)低于粗晶工业纯钛(8.6×10-6s-1)，抗蠕变性能优于粗晶工业纯钛；位错滑移机理是其主要蠕变变形机理，蠕变断裂机制为韧性断裂。

Abstract:

Ultra-fine grained commercially pure (CP) Ti with an average grain size of 120 nm was fabricated by equal channel angular pressing (ECAP) following cold rolling (CR) and swaging at room temperature. Uniaxial tensile creep tests, transmission electron microscope and scanning electron microscope were applied to investigate the creep behavior and mechanism of ultra-fine grained CP Ti. The results showed that a significant creep deformation at room temperature occurred in the ultra-fine grained CP Ti. The steady creep rate increased from 2.8×10-7 s-1 to 1.5×10-4 s-1 as the creep stress increased from 640 MPa to 760 MPa. Ultra-fine grained CP Ti had lower steady creep rate than the coarse-grained CP Ti at the same stress level, which indicated that ultra-fine grained CP Ti had higher creep resistance. The creep mechanism of ultra-fine grained CP Ti is dislocation movement. The creep fracture morphology of ultra-fine grained CP Ti exhibited ductile fracture with dimples.