Influence of Prior Austenite Grain Size on Gleeble Flow Stress Measurement

The mechanical properties of any alloy are greatly impacted by its grain size and microstructural features. Not only can grain size influence yield strength, as described through the Hall Petch relationship, but in small sample cross-sections, grain size can also influence the accuracy of mechanical testing results. Very large grain size in the test samples would result in too few grains per cross-section area and could skew the results of our tests. In order to determine whether Gleeble testing on AISI 9310 normalized steel samples with reduced diameter sections of 3 mm was valid, we analyzed the prior austenite grain size and phase distribution in the samples prior to testing and after testing. Several etchants were used to reveal the grain boundaries of the samples including Vilella’s Reagant, 2% Nital, and a Sodium Bisulfite-based etchant. Metallographic samples were analyzed using optical light microscopy and image analysis software. Results of this analysis will allow us to determine minimum diameter for these steel samples for future Gleeble testing.