采用连续点式锻压激光快速成形技术进行了TC11钛合金厚壁零件成形实验,利用OM、SEM等手段研究了连续点式锻压激光快速成形TC11钛合金的组织和力学性能。结果表明,TC11钛合金试样内部的等轴晶晶粒尺寸均匀,平均晶粒尺寸48.7 μm。等轴晶的晶界α相连续,晶内是初生α相板条+β转变组织组成的双态组织。在连续点式锻压激光快速成形过程中,连续点式锻压时,TC11钛合金厚壁零件的表层变形区深度约为1.5 mm,变形量为20%。在连续点式锻压冷变形TC11钛合金上表面沉积新层过程中,当激光束扫描经过时,熔池热影响区中约1 mm厚(4层)冷变形TC11钛合金被加热到钛合金β转变温度之上,并在0.86 s内完成再结晶。力学性能结果表明,与TC11钛合金锻件相比,连续点式锻压激光快速成形的TC11钛合金的强度高,而塑性低。断口形貌分析表明,晶间断裂是导致TC11钛合金塑性差的主要原因。

The titanium alloy parts, which have been formed by traditional laser additive manufacturing (LAM) method, usually have obviously different microstructure from wrought microstructure of titanium alloy and show room temperature mechanical anisotropy. In order to make the LAMed titanium alloy parts get the same microstructure and mechanical properties as wrought titanium alloy, a new technology of LAM called consecutive point-mode forging and laser rapid forming (CPF-LRF) has been proposed. During CPF-LRF process, deposited TC11 titanium alloy by laser rapid forming (LRF) was deformed by consecutive point-mode forging (CPF), and then on the surface of the deformed TC11 titanium alloy, new LRF process started over again. Both LRF and CPF were performed alternatively throughout the process of the fabrication of a TC11 titanium alloy part. Microstructures and mechanical properties of the CPF-LRFed TC11 alloy sample have been investigated. The average grain size of equiaxed grains of the CPF-LRFed TC11 alloy sample is 48.7 μm. The equiaxed grains have continuous grain boundary α phase. The microstructure of the equiaxed grain is bimodal microstructure consisting of primary α phase lath and transformed β. During CPF-LRF process, being plastically deformed by CPF, the surface deformation zone of the thick-wall TC11 titanium alloy part is 1.5 mm depth and its deformation degree is 20%. During a new layer deposited on the surface of the CPF cold deformed TC11 titanium alloy part, when laser beam scans through, about 1 mm thick (four layers) cold deformed titanium alloy in the heat affected zone of laser melting pool is heated up above β-transus temperature of TC11 titanium alloy in which static recrystallization complete within time interval of 0.86 s. The mechanical properties indicate that compared with the tensile properties at room temperature of TC11 alloy forged piece, the CPF-LRFed TC11 alloy has higher strength and less ductility. Fracture analysis indicates that intergranular fracture is mainly responsible for the poor ductility of CPF-LRFed TC11 alloy.