DYNAMIC AND QUASI-STATIC TORSIONAL BEHAVIOR OF TUNGSTEN HEAVY ALLOY SPECIMENS FABRICATED THROUGH SINTERING, HEAT-TREATMENT, SWAGING AND AGING

Dynamic and quasi-static torsional deformation behavior of a 93W-4.9Ni -2.1Fe tungsten heavy alloy (WHA) was investigated in order to evaluat e the possibility of forming adiabatic shear bands. Dynamic torsional tests were conducted using a torsional Kolsky bar for the four WHA spe cimens fabricated through each processing condition, e.g. sintering, h eat-treatment, swaging, and aging, and then the test data were compare d with those of the quasi-static tests. The dynamic torsional test res ults indicated that the shear stress increases, while the shear strain decreases, with the maximum shear stress increasing in the order of t he as-sintered, the as-heat-treated, the as-swaged, and the as-aged sp ecimens. The as-swaged and the as-aged specimens showed a higher possi bility of the adiabatic shear band formation because of the abrupt dro p of shear stress between the maximum shear stress and the final fract ure points and because of the radical reduction of shear strain at the maximum shear stress point. The observation of the deformed areas of the dynamically fractured torsional specimens revealed that the shear deformation was homogeneously distributed in a wide area in the as-sin tered and the as-heat-treated specimens, whereas it was concentrated o n the central area of the gage section in the as-swaged and the as-age d specimens. This torsional behavior correlated well with the shear st ress-shear strain curves, suggesting that the torsional Kolsky bar tec hnique is a good tool for helping evaluate the possibility of the adia batic shear band formation. (C) 1998 Elsevier Science S.A. All rights reserved.