Nanomechanical mapping for individual phase performance as a function of environmentThursday (27.09.2018) 11:45 - 12:00 S1/01 - A03 Part of:
Nanoscale probing techniques are becoming a common method for solving problems in complex materials or multiphase materials. Fundamental metallurgical studies to mineralized biocomposites studied in academia and industrial researchers involved in dissimilar welding both find themselves trying to find failure and strength controlling mechanisms at very fine scales. One technique for this type of mapping is high speed nanoindentation. While “standard” nanoindentation is truly a high throughput technique in comparison to most other mechanical testing mechanisms, high speed nanoindentation increases indentation though put by a factor of 1000. Here, arrays of indents can be performed on samples in order to generate a property map, and in the case of many materials, used to generate statistical averaging of measurements with traceability back to the original location via SPM scanning. Correlating the property map back to structural properties and local chemistry, via techniques like EDS or EBSD is also possible. This technique can also be coupled to local environment, such as cooling and heating. Here, a fundamental study in a low carbon, 1018, steel is presented. This material is non-exotic, but plays a large role in the nuts and bolts of everyday life. 1018 steel is a two phase steel, containing both ferrite and pearlite phases that are easy to distinguish both via in contact SPM and high speed mapping of the steel, with the high C pearlite being much harder than the ferrite. This material also exhibits a ductile to brittle temperature transition at -5C via Charpy impact testing. However, when the individual phases can be looked at separately, this transition can then be looked at locally. Besides a rapid increase in hardness, as the ability to cross-slip decreases, there is a change in the behavior of the load-displacement curve from smooth to heavily serrated flow dominated by pop-in behavior.