反复轧制过程中TA1纯钛板的组织演化及强化机制

采用反复轧制工艺制备了超细晶TA1纯钛板。通过金相、透射电镜、X射线衍射、扫描电镜等手段,分析了纯钛板在反复轧制过程中,不同的应变量所对应的组织形貌特点,并测试了强度、塑性,观察了宏观断口与微观形貌。结果表明:纯钛在常规轧机上经过反复轧制可显著细化晶粒,晶粒尺寸由轧制前的80μm降至120 nm;强度则随着轧制应变量的增加而提高,当Von Mises等效应变为2.4时,平均屈服强度提高到678 MPa,是轧制前粗晶的3倍多;位错及其交互作用是细化晶粒的主要机制,在高密度位错区域由于位错的交互作用而形成了位错胞和亚晶粒,最终演变成超细晶粒;细晶强化和加工硬化是导致纯钛轧制后强度显著提高的主要原因。

Microstructure Evolution and Strengthening Mechanism of Ultrarefine-grained Pure Titanium Fabricated by Repeated Rolling

The microstructure, mechanical behaviors and fracture morphology of TA1 pure titanium subjected to repeated rolling have been investigated using optical microscopy （ OM）, transmission electron microscopy （ TEM）, X- ray diffraction （XRD）, tensile tests and scanning electron microscopy （SEM）. The results show that the average grain size of commercially pure （CP） titanium decreased from 80 ~m （before rolling） to 120 nm by repeated rolling. With the strains increasing, the strength of CP Ti increased. The average yield strength of CP Ti is 678 MPa, when the Von Mises strain is larger than 2. 4, which is 3 times higher than that of coarse-grained titanium. The TEM results show that dislocation ceils evolve into subgrains and then ultrafined grains which means that dislocation interaction dominates grain refinement of CP Ti during repeated rolling. The higher strength of uhrafined-grained titanium than coase-graine titanium results from grain refinement and strain hardening which is caused by severe plastic deformation during repeat- ed rolling.