Microstructure and properties of additively manufactured Ti-6Al-4V alloy under dynamic impact

Abstract

An investigation into the rate-dependent mechanical response and microstructural evolution of Ti-6Al-4V produced by additive manufacturing (AM) is presented. Three strain rate levels (1439 s−1, 2334 s−1, and 3302 s−1) were applied via Split Hopkinson Pressure Bar (SHPB) testing. The as-built alloy consists mainly of α phase with a smaller fraction of β phase, exhibiting both basketweave and colony microstructural patterns. Under high-rate compression, the material’s yield strength and dynamic compressive strength rise with increasing strain rate, revealing a clear positive strain rate hardening effect. Adiabatic shear band (ASB) formation occurs under all tested strain rates. Crack initiation and subsequent propagation are primarily governed by the nucleation, growth, and coalescence of micro-voids along these ASBs. Furthermore, higher strain rates promote secondary shear band formation and increase crack density, accelerating dynamic failure.