CM01.12.06 : Microstructurally Resolved Ductile-to-Brittle Transitions in Low Carbon Steel by High Speed Nanoindentation Mapping

5:00 PM–7:00 PM Apr 5, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Eric Hintsala1 Douglas Stauffer1

1, Bruker NI, Eden Prairie, Minnesota, United States

Nanoscale probing techniques are becoming a common method for solving problems in complex multiphase materials. Diverse topics, from fundamental metallurgical studies and mineralized biocomposites in academia to 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 this throughput by a factor of 1000. Thus, large arrays of indents numbering in thousands can be used to generate high resolution property maps. This can also produce useful statistics which can be selected and compared from different regions of the map with traceability back to the original location via SPM scanning. This technique can also be coupled to the 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 carbon pearlite being much harder than the ferrite. This material also exhibits a ductile to brittle temperature transition at -5C via Charpy impact testing. However, the ability to explore this phase by phase and at a local scale reveals changes in the load-displacement curve from smooth to heavily serrated flow dominated by pop-in behavior.