Influence of microstructure on adiabatic shear localization of pre-twistedtungsten heavy alloys

The influence of microstructure of pre-twisted tungsten heavy alloy (WHA) o n the adiabatic shear localization under dynamic loading was investigated e xperimentally. A combined compression and shear load was applied to a cylin drical specimen with its axis inclined to the loading axis by use of a spli t Hopkinson pressure bar (SHPB) apparatus which generates a strain rate as high as 10(3) s(-1). A relatively narrow shear band was formed approximatel y along the maximum shear stress direction, followed immediately by catastr ophic fracture. Electronic microscopy and optical microscopy observations w ere made on the fracture surfaces and the microstructures of un-fractured s pecimens. It is found that the initial microstructures such as the aspect r atio and orientation of the W-grains have significant influence on the tend ency to the shear band formation. The adiabatic shear band has general tren ds to propagate along the Ni-Fe matrix and more energy is needed to sheer t he tungsten grains. It is suggested that further studies on the optimizatio n of microstructure and control of the fabricating process to promote the s hear band formation be conducted in order to improve the penetration perfor mance of the tungsten heavy alloy. (C) 2000 Elsevier Science Ltd. All right s reserved.