Influence of microstructure on adiabatic shear localization of pre-twisted tungsten heavy alloys

The influence of microstructure of pre-twisted tungsten heavy alloy (WHA) on the adiabatic shear localization under dynamic loading was investigated experimentally. A combined compression and shear load was applied to a cylindrical specimen with its axis inclined to the loading axis by use of a split Hopkinson pressure bar (SHPB) apparatus which generates a strain rate as high as 10(3) s(-1). A relatively narrow shear band was formed approximately along the maximum shear stress direction, followed immediately by catastrophic fracture. Electronic microscopy and optical microscopy observations were made on the fracture surfaces and the microstructures of un-fractured specimens. It is found that the initial microstructures such as the aspect ratio and orientation of the W-grains have significant influence on the tendency to the shear band formation. The adiabatic shear band has general trends to propagate along the Ni-Fe matrix and more energy is needed to sheer the tungsten grains. It is suggested that further studies on the optimization of microstructure and control of the fabricating process to promote the shear band formation be conducted in order to improve the penetration performance of the tungsten heavy alloy. (C) 2000 Elsevier Science Ltd. All rights reserved.