The compressive failure of aluminum nitride considered as a model advanced ceramic

Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

“…Recent microcompression experiments show that brittle ceramics could be plastically deformed by dislocations at small length scale [25,27,30]. For AlN, both single-crystal and polycrystalline samples at a macroscopic length scale always fails in a brittle manner at room temperature prior to plastic yielding although hydrostatic stress state introduced by mechanical confinements can significantly suppress the brittle failure and gives rise to dislocation plasticity [11][12][13]. Different from previous observations, in this study we found that brittle AlN can plastically flow like metals with considerable dislocation plasticity when specimen sizes are smaller than a critical value of $4 lm, presenting a remarkable size-induced brittle-to-ductile transition in this high-strength covalently-bonded ceramic.…”

“…As exceptions, only a handful of ceramics show room-temperature plasticity via anomalous deformation processes, such as martensitic transformation [1,2], kink bands [3] and grain boundary sliding [4,7], or subjected to extreme loading conditions, such as shock [6,8], high pressure [9][10][11] and strain confinement [11][12][13]. Nevertheless, large dislocation plasticity is rarely seen in high strength ceramics during room-temperature uniaxial deformation [14].…”

“…Moreover, it has been reported that hydrostatic confinement facilitates dislocation plasticity of AlN [11,13]. However, the room temperature plasticity cannot be retained in confinement-free AlN, which always fails in a brittle manner without any plastic strain under quasi-static uniaxial deformation [11,[15][16][17][18].…”

The influence of mechanical and microstructural properties on the rate-dependent fracture strength of ceramics in uniaxial compression

“…At these low strain rates, the peak stress that a ceramic can support prior to fracture is a characteristic value called the quasistatic strength. At strain rates above the critical value, however, the fracture strength of these materials exceeds quasistatic values and is extremely rate sensitive [5][6][7]. Mechanisms M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 for this rate sensitivity have been discussed, for example, by [2,8,9], and it has been noted that the critical transition strain rate and quasistatic strength are intimately related to the properties of ceramics; in the present study we investigate this relationship.…”

A Scaled Model Describing the Rate-Dependent Compressive Failure of Brittle Materials

“…In brief, that work showed that the dynamic compressive failure process is controlled by the interactions of three terms: the initial defect distribution, crack growth dynamics and crack-crack interactions, and the coupling of these three terms with the superimposed rate of loading. That model describes the increase in the strength that is often observed in brittle materials subjected to uniaxial compression at high strain rates [3,4,5,6,7,8,9,10,11,12,13]. This work develops a model that captures the behavior of brittle solids in an appropriately scaled form [14].…”