Excellent ballistic impact resistance of Al0.3CoCrFeNi multi-principal element alloy with unique bimodal microstructure

Multi-principal element alloys represent a new paradigm in structural alloy design with superior mechanical properties and promising ballistic performance. Here, the mechanical response of Al0.3CoCrFeNi alloy, with unique bimodal microstructure, was evaluated at quasistatic, dynamic, and ballistic strain rates. The microstructure after quasistatic deformation was dominated by highly deformed grains. High density of deformation bands was observed at dynamic strain rates but there was no indication of adiabatic shear bands, cracks, or twinning. The ballistic response was evaluated by impacting a 12 mm thick plate with 6.35 mm WC projectiles at velocities ranging from 1066 to 1465 m/s. The deformed microstructure after ballistic impact was dominated by adiabatic shear bands, shear band induced cracks, microbands, and dynamic recrystallization. The superior ballistic response of this alloy compared with similar AlxCoCrFeNi alloys was attributed to its bimodal microstructure, nano-scale L12 precipitation, and grain boundary B2 precipitates. Deformation mechanisms at quasistatic and dynamic strain rates were primarily characterized by extensive dislocation slip and low density of stacking faults. Deformation mechanisms at ballistic strain rates were characterized by grain rotation, disordering of the L12 phase, and high density of stacking faults.

Penetration Damaging Behavior of ATI425 Titanium Alloy

The penetration damaging behavior of ATI425 titanium alloy was studied by 7.62 mm diameter armor piercing projectiles. The damage characteristics and the mechanism were analyzed by observing and analyzing the craters of ATI425 titanium alloy target. It can be found that local temperature-rise of the target plate occurred, even sputtering phenomenon in the opening stage. The shear bands extended upward along the cater wall could be seen in the stable stage. The large non-homogeneous deformation in adiabatic shear bands caused microcracks and micropores. A large number of macro-cracks were observed on the side wall and at the bottom of the crater.

Experimental and microstructure analysis of the penetration resistance of composite structures

Composite structures (SiC/UHMWPE/TC4; SiC/TC4/UHMWPE) were designed using silicon carbide (SiC)ceramics, ultra-high-molecular-weight polyethylene (UHMWPE) laminate, and titanium alloys (TC4s). Penetration experiments and numerical simulations were carried out to study the anti-penetration mechanism and energy characteristics of the composite structures, and the microstructure of the TC4 was analyzed. The results show that the two composite structures designed have advantages in reducing mass and thickness. The energy proportion of the TC4 is the largest among the three materials, which mainly determines the anti-penetration performance. The microstructure of the TC4 in composite structure I shows rough edges of bullet holes, a large number of adiabatic shear bands (ASBs), ASB bends and bifurcates, and many cracks, which lead to spalling damage of the TC4. The microstructure of the TC4 in composite structure II shows flat edges of bullet holes, several straight ASBs, and no cracks, which leads to brittle fragmentation. The initiation, expansion, combination of ASBs and cracks lead to more energy consumption. Therefore, the combination form of composite structure I can give full play the energy dissipation mechanism of the TC4 and has better anti-penetration performance than composite structure II.