Indentation grid analysis of nanoindentation bulk and in situ properties of ceramic phases

Abstract

Composites properties are often derived from the proper-ties of the constituent phases measured in bulk forms.However, in situ properties can be different from thosemeasured in bulk as a consequence of material processing[1–3]. In ceramic composites, for example, spurious phasescan form due to the chemical interaction of differentpowders. The knowledge of in situ properties would allowa better characterization and tailoring of composites per-formances. Many ceramic composites are particle-reinforced composites so that the evaluation of in situproperties involves measurements in very small volumes.For some mechanical properties, this can be accomplishedby nanoindentation tests. By nanoindentation, singlemicrostructural elements can be tested as grains in poly-crystals [4, 5] or single phases in composites [3, 6–8]. Inthis work, a comparison between nanoindentation bulk andin situ properties of some ceramic phases will be presented.Generally, in situ properties are evaluated by imaging theindentation marks, for example using a scanning electronmicroscope (SEM), to detect which phase was indented.Besides this traditional technique, which can be timeconsuming especially when indentations are tiny as ithappens in hard phases like advanced ceramics, in situproperties will be estimated applying a new type of anal-ysis to nanoindentation data [9–11]. According to this newanalysis, the mechanical properties of the constituentphases of a composite can be easily derived from a sta-tistical analysis of nanoindentation results without havingto image where indentation marks were placed. Basically,the analysis consists in fitting the experimental dataaccording to a proper number of statistical distributionswhose central values correspond to the specific propertiesof each phase. Constantinides et al. [10] called this analysisindentation grid (IG). In this work, IG will be applied toparticle-reinforced ceramic composites, some based onwell-known phases, such as MoSi