Role of Microstructural Features in Toughness Improvement of Zirconia Toughened Alumina

Abstract

Ceramics constitute an integral part of highly efficient armours due to their low density, high hardness, strength and stiffness. However, they lack toughness and multi-hit capability. Therefore, zirconia toughened alumina is investigated. The hardness is evaluated using Vickers, Knoop and instrumented indentations, while the fracture toughness is evaluated using the indentation technique and Charpy tests. The strength is evaluated using ring-on-ring, four point bend and drop weight tests. The Young's modulus is evaluated using the unloading instrumented indentation curves. Microstructure, porosity and density are characterised using ultrasonic scanning, Archimedes principle, optical and scanning electron microscopy. Results show an indentation size effect on all mechanical properties. A substantial improvement in toughness is achieved through retardation of crack initiation by tetragonal-to-monoclinic phase transformation in zirconia particles, crack deviation thanks to appropriate grain structure, as well as energy absorption by densification due to remaining porosity. This improved toughness is expected to promote multi-hit capability.

Preparation and Fracture Analysis of Advanced Layered Composite with Graphene-Coated Alumina Nanofibers

“…4d). A similar event was described in the literature [9]. Although pores are generally recognized as detrimental to the strength of ceramics, it has been proven that uniformly distributed small-size pores can indeed provide good ballistic performance [9].…”

“…Although pores are generally recognized as detrimental to the strength of ceramics, it has been proven that uniformly distributed small-size pores can indeed provide good ballistic performance [9]. Thanks to the energy absorption by local pore collapse and densification, pores can retard the initiation of relatively large fractures causing cracks making them potentially beneficial [9]. The average values of relative density, Young's modulus, and Vickers hardness of the prepared materials are summarized in Table 2.…”

Comparative Study on the Performance of ZTA Cutting Tool with the Addition of Different Particle Size of MgO Additive

“…Zirconia toughened alumina (ZTA) composite with an enhancement of toughness produced by the addition of zirconia particles to the alumina matrix. The toughness of the alumina composites improved from 2.69 MPam 1/2 to 4.90 MPam 1/2 compared to alumina composite alone [1]. Although the composites able to improve in toughness, the hardness is still considered low to meet the optimum machining conditions.…”