TC32钛合金的动态力学性能及损伤特点

采用分离式霍普金森压杆技术对TC32钛合金片层组织、双态组织、网篮组织试样进行了动态剪切实验,通过光学显微镜、扫描电镜研究了TC32钛合金不同组织的损伤特点。结果表明：片层组织、双态组织、网篮组织的临界应变率分别为2400 s-1,2700 s-1与2600 s-1,与网篮组织和片层组织相比,双态组织具有最优的综合动态力学性能。三种组织均观察到了绝热剪切带,并且绝热剪切破坏都要经过微孔洞的形核、长大与相互联结的过程,微孔洞的萌生与长大优先沿着绝热剪切带与基体的界面位置。片层组织绝热剪切带与基体的界面塑性流变特征不明显,并且在该区域观察到了呈快速扩展特征的长裂纹。双态组织绝热剪切带及与基体界面呈纤维状,周围组织在剧烈剪切力的作用下呈明显的塑性流变特征,等轴状或者椭圆型的初生α相被严重拉长变形,微孔洞也容易在α/β转变基体的界面处形核。网篮组织与双态组织的损伤特点类似,但与片层组织和双态组织不同的是,当网篮组织中具有规则排列的针状α相与绝热剪切带垂直时,微孔洞也容易在该处萌生。绝热剪切带内部组织主要是由细小的等轴晶粒组成,形成机制尚无统一定论。

Investigation of Dynamic Mechanical Behavior and Damage Characteristics in TC32 Alloy

The dynamic shearing experiment was been done by using split Hopkinson pressure bar(SHPB) technique in TC32 alloy with lamellar, bimodal and basket microstructures. The damage Characteristics of TC32 alloy was investigated by using optical micro-scope(OP) and scanning electron microscopy(SEM). The results show that the critical fracture velocity is 2400 s-1, 2700 s-1, and 2600 s-1 for lamellar, bimodal, and basket microstructures respectively. The bimodal microstructure exhibit the best Dynamic mechani-cal behavior compared with the other two microstructures. Adiabatic shear bands( ASBs) and microvoids initiation, growth, and coales-cence to damage in adiabatic shear bands( ASBs) were observed in all of three microstructures. Also, microvoids initiation and growth are prior to the interface between ASBs and matrix. Investigation indicated that plastic flow characteristic is not obvious at the interface between ASBs and matrix, which observed long crack in lamellar microstructure. In bimodal microstructure, fibrous a adiabatic shear bands( ASBs) and surrounding region are shown. Because of strong shear deformation, the plastic flow characteristic appears clearly, and primary α phase was elongated. Microvoids initiation is also prior to theα/βphase boundaries. The damage characteristics of bas-ket microstructure are similar to bimodal microstructure. But unlike lamellar and basket microstructures, the microvoids are initiatied when the acicular primary α phase arranged in order is perpendicular to the adiabatic shear bands( ASBs) in lamellar microstructure. ASBs is mostly consisted of equiaxed grains, and the deformation mechanism still wasn't defined.