An investigation of equibiaxial flexural strength and hardness properties of Al2O3–Ni nanocomposites based microstructures with ZrO2 and Cr2O3 additives

Abstract

The investigation of new ceramics and ceramic composites to overcome the inadequacies of monolithic ceramics without using costly techniques and equipment is essential for developing ceramic armor components. The aim of the research was analyzing the mechanical properties (elastic modulus, flexural strength, and hardness) of Al2O3/1 vol% Ni nanocomposites with 5 vol% ZrO2 or 1 vol% Cr2O3 additives and estimating their performance by comparing with the pure Al2O3, Al2O3/ZrO2 composite, and Al2O3/Cr2O3 ceramic system for armor applications. The heterogeneous precipitation method was used to obtain nano-sized metal particles in the ceramic matrix for the Ni-containing compositions. Equibiaxial flexural tests were conducted for strength measurements and stored energy at failure was estimated by using the theoretical deflection of the cylindrical plate; also, post-failure total crack lengths were measured. Simultaneous addition of Ni and ZrO2 on Al2O3 matrix resulted in the highest hardness (25.5 ± 1.0 GPa) and flexural strength (367 ± 34 MPa) compared to other compositions because of the hardening effect of Ni and the grain boundary strengthening mechanism. Moreover, this composition showed the highest resistance to fragmentation as evidenced by the shortest crack length per stored energy at failure. Cr2O3 addition also provided remarkable results related to the solid solution formation for both the pure Al2O3 and Al2O3/Ni composites. By this comparative study, different compositions with high mechanical properties have been introduced as the potential candidates to be used in armor applications with static tests giving an indication about ballistic performance.