The effects of loading direction on the dynamic impact response of additively manufactured M350 maraging steel-Al0.5CoCrFeNi1.5 hybrid plates

Abstract

Despite the impressive impact strength of maraging steels, which informs their application in the defence industry, they are highly susceptible to cracking resulting from adiabatic shear band (ASB) nucleation when subjected to dynamic loading. Hence, a potential solution to mitigate this problem is needed. In this study, a hybrid plate containing layers of M350 maraging steel and Al_0.5CoCrFeNi_1.5 high entropy alloy was fabricated using laser-based directed energy deposition (L-DED) additive manufacturing with the aim of combining the high impact strength of M350 maraging steel with the ductility and ASB-resistant properties of Al_0.5CoCrFeNi_1.5. To determine the effect of loading direction on the impact strength and absorbed energy of the hybrid specimens, cylindrical specimens, with the layers oriented longitudinally and transversely to the cylinder's axis, were cut out of the hybrid plate. High-strain rate testing was performed using an instrumented split-Hopkinson pressure bar (SHPB) to determine the dynamic mechanical response of the specimens. Statistical analyses of the results using generalised additive models (GAM) showed that layer orientation with respect to the direction of impact significantly affects the hybrid specimens' impact strength and absorbed energy. The longitudinally oriented specimens demonstrated superior impact strength across all tested impact momenta. However, the transversely oriented specimens showed higher absorbed energy up to an impact momentum of 32.8 kg ms⁻¹. The Al_0.5CoCrFeNi_1.5 layer contributed significantly to energy absorption, strain hardening, and the inhibition of ASB propagation in the hybrid specimens.