Dynamic impact response of additively manufactured monolithic and hybrid armour materials

Although M350 maraging steel is widely used for defence, automotive, medical and aerospace applications due to its exceptional strength and toughness, it is susceptible to cracking in high strain rate conditions. To address this limitation, a novel hybrid plate was fabricated using laser-based directed energy deposition (DED) additive manufacturing by combining layers of M350 maraging steel and Al 0.5 CoCrFeNi 1.5 high-entropy alloy (HEA). Then, its dynamic impact response was compared with those of the constituting monolithic alloys. Samples of the monolithic and hybrid materials were heat-treated. M350 maraging steel and the hybrid specimens were austenitized at 850 °C for 0.5 h, water-quenched, and artificially aged at 535 °C for 0.5 h, while the monolithic Al 0.5 CoCrFeNi 1.5 HEA was normalized at 700 °C for 1.5 h and air cooled to room temperature. Both heat-treated and as-built materials were subjected to dynamic impact tests at impact momenta that varied from 24.3 to 47.6 kg.ms⁻¹ using an instrumented split Hopkinson pressure bar (SHPB). The heat-treated hybrid specimens demonstrated impressive energy absorption capability, outperforming their monolithic M350 maraging steel counterparts by 46.6 % and 59.4 % at impact momenta of 32.8 kg.ms −1 and 38.8 kg.ms −1 respectively. These heat-treated hybrid specimens survived testing up to 43.8 kg.ms −1 , while their monolithic M350 maraging steel counterparts began to fracture at 38.8 kg.ms −1 . Microstructural analyses revealed that transformed adiabatic shear bands formed more readily in monolithic M350 maraging steel than in the hybrid specimens leading to early catastrophic failure. These findings demonstrate a new strategy for mitigating the cracking propensity of maraging steel in defense applications through additive manufacturing of hybrid maraging steel-HEA structures. • Heat-treated hybrid specimens absorbed 168 %, 47 % and 59 % more energy than M350 MS at 24, 32 and 39 kg.ms -1 , respectively. • Heat-treated hybrid specimens withstood impact up to 43.8 kg·ms⁻¹; M350 MS fractured earlier at 32.8 kg·ms⁻¹. • The HEA layer delayed ASBs and improved ductility, while the M350 MS layer contributed strength and hardness. • Hybrid specimens exhibited ductile fracture in the HEA layer and brittle cleavage in M350 MS. . • First comparative dynamic impact study of DED-fabricated maraging steel-HEA hybrid specimens vs monolithic maraging steel.