REVERSE-BALLISTIC IMPACT STUDY OF SHEAR PLUG FORMATION AND DISPLACEMENT IN TI6AL4V ALLOY

Gas-gun reverse-ballistic experiments have been performed in which Ti6 Al4V alloy disks were impacted onto smaller diameter, hardened steel r ods to push out shear plugs from the disk material. The range of disk velocities was 219-456 m/s. For each experiment, the disk, plug, and r od were soft recovered after impact. Below 290 m/s, the plugs were pus hed only partway through the disks, but localized shear bands outlinin g the plug shapes were easily recognized in metallographic sections. O ptical and scanning electron microscopies were used to determine shear zone widths and to describe microstructural details associated with t he primary shear zones. There is evidence for appreciable adiabatic he ating and consequent thermal softening and melting of material in the main shear zone. A simple model is used to relate the observed plug di splacements to the impact velocities and to provide estimates of sever al features: the shear zone strength, the threshold energy for shear p lug displacement, and the threshold energy for shear plug separation. Clear evidence is presented of molten material having been produced as part of the plug separation process.