Authors: R D K Misra P K C Venkatsurya M C Somani L P Karjalainen
Publish Date: 2012/08/09
Volume: 43, Issue: 13, Pages: 5286-5297
Abstract
We have used the recently adopted concept of phase reversion to obtain grain size from the nanograined/ultrafinegrained NG/UFG to fine grain FG regime by varying temperature–time annealing sequence of cold deformed metastable austenite The phasereversion induced NG/UFG structure was characterized by high strengthhigh ductility combination The concept of phase reversion involves severe cold deformation of metastable austenite to generate straininduced martensite Upon annealing martensite transforms back to austenite through a diffusional reversion mechanism with NG/UFG submicron grains SMG or FG structure depending on the annealing condition Depthsensing nanoindentation experiments were combined with electron microscopy to elucidate the dependence of grain size from nanograin/ultrafinegrain NG/UFG to coarse grain CG regime on the deformation mechanisms There was distinct transition in the deformation mechanism from intense mechanical twinning and stacking faults in NG/UFG structure to straininduced martensite formation at the intersection of shear bands in the CG structure The transition in the deformation mechanism is discussed in terms of increase in austenite stability with decrease in grain size
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