利用分离式霍普金森压杆(SHPB)装置在3 900 s-1应变率条件下对Ti-6Al-4V合金进行动态加载,获得完全分离的断裂试样.使用扫描电子显微镜对试样的断裂特征进行观察.结果表明:试样中出现绝热剪切断裂,试样断口上交替分布着两个不同特征的典型区域(韧窝区及平滑区).其中,韧窝区由微孔洞形核、长大并最终连接形成,表现出韧性断裂特征.在平滑区观察到超细晶粒(UFGs),且晶粒间可观察到微裂纹,说明平滑区由微裂纹沿晶界扩展形成,表现出脆性断裂特征.由此可知,Ti-6Al-4V合金在动态加载过程中沿绝热剪切带发生的断裂失效过程不均匀,韧性及脆性两种断裂模式的共同作用导致该合金样品的最终断裂.%Separated specimens of Ti-6Al-4V alloy were dynamically loaded at a strain rate of 3 900 s-1 using a split Hopkinson pressure bar (SHPB) apparatus.The fracture features of the separated specimens were investigated by a scanning electron microscope.The results show that adiabatic shear failure occurs in the tested specimens,and two typical areas (dimple and smooth areas) with different features are alternatively distributed on the whole fracture surface.The dimple areas originate from voids generation and coalescence,exhibiting ductile fracture characteristics.Simultaneously,ultrafine grains (UFGs) and microcracks among grains are observed on the smooth areas,indicating that the emergence of UFG areas is caused by the propagation of microcracks along grain boundaries and exhibits brittle fracture characteristics.Fracture occurring in adiabatic shear bands is not uniform and ultimate rupture is resulted from ductile and brittle fracture modes.
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