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采用累积叠轧技术制备具有超细晶组织的TC4钛合金,考察了叠轧工艺对界面结合和微观组织的影响规律以及该过程中α/β两相钛合金的变形机制,分析了叠轧工艺对TC4合金力学性能的影响。结果表明,TC4合金累积叠轧过程中需要足够的加热温度(近于720℃)、防氧化处理以及多层数大下压量的轧制工艺,才能获得良好的界面结合,但是界面处存在O含量较高的硬化层。随着叠轧温度和叠轧层数的增加,TC4板材的结合界面逐渐消失并具有较高的结合强度。累积叠轧过程是协同变形和剪切变形综合作用的结果,即变形初期晶界β相由长条状转变为短片状且晶界发生滑移,而在变形程度较高时组织中有大量的剪切带,此过程存在大量局部变形以适应大塑性变形过程。变形组织中存在局部等轴组织(约300 nm)和拉长的变形结构(约400 nm),其中等轴组织是由于变形温度、局部剪切变形和局部过热作用而发生再结晶形成的。叠轧板材在厚度方向存在组织性能不均匀现象,在结合界面处硬度较高,随着叠轧层数的增加硬度逐渐趋于一致。同时随着叠轧层数的增加,TC4合金的抗拉强度逐渐增加,在叠轧16层后抗拉强度达到1325 MPa,塑性降低为5.4%。在叠轧层数较少时,断裂过程表现为韧性断裂,随着叠轧层数的增加,断口形貌逐渐转变为韧窝断口和准解理断口的综合形貌。
The TC4 titanium alloy with ultra-fine grain structure was prepared by accumulative roll-rolling technique. The influence of the rolling process on the interfacial bonding and microstructure was investigated. The deformation mechanism of the α / β-phase titanium alloy during the process was investigated. Effect on the Mechanical Properties of TC4 Alloy. The results show that good interfacial bonding can be obtained only when sufficient heating temperature (near 720 ℃), anti-oxidation treatment and multi-layer rolling process are needed in the process of accumulative rolling. However, there are O High content of hardened layer. With the increasing of the roll-stand temperature and the number of lapping layers, the bonding interface of TC4 sheet gradually disappeared and had higher bonding strength. Accumulative stacking and rolling process is the result of synergetic deformation and shear deformation. That is, the β phase in the initial stage of deformation changes from long strip to short strip and the grain boundary slips, while in the high degree of deformation, there is a large amount of Shear zone, a large number of local deformation in this process to adapt to the process of plastic deformation. In the deformed structure, there are local equiaxed structures (about 300 nm) and elongated deformed structures (about 400 nm), of which isostructure is recrystallized due to deformation temperature, local shear deformation and local overheating. Laminated sheet in the thickness direction of the existence of uneven microstructure, the interface at the junction of higher hardness, with the increase in the number of laminated roll hardness gradually become consistent. At the same time, the tensile strength of TC4 alloy gradually increases with the increase of the number of laminated layers. The tensile strength of the TC4 alloy reaches 1325 MPa and the ductility decreases to 5.4% after 16 layers are rolled. When the number of stacked layers is small, the fracture process shows ductile fracture. With the number of laminated layers increasing, the fracture morphology gradually changes to the comprehensive morphology of dimple fracture and quasi-cleavage fracture.