Partial transformation of austenite in Al–Mn–Si TRIP steel upon tensile straining: an in situ EBSD study

Abstract

The transformation of austenite to martensite in an Al–Mn–Si transformation-induced plasticity steel was investigated with in situ electron backscatter diffraction (EBSD) measurements under tensile straining. The visualisation of the microstructure upon straining allows for an investigation of the stability of austenite grains against strain-induced transformation, with particular focus on the grain size and the location of the austenite grains. The findings confirm that size and location of austenite grains are significant parameters for their stability. Small austenite grains were observed to be more stable than large grains, while austenite grains located beside bainitic ferrite are the most stable. Moreover, it is demonstrated that austenite grains transform gradually.

Keywords:

• Austenite-to-martensite phase transformation
• EBSD
• In situ tension test
• TRIP steel

Financial support from the NIMS Internship Program at the National Institute for Materials Science in Japan is gratefully acknowledged. The Danish Research Council for Independent Research is also acknowledged for financial support.

Notes

† The plate-morphology of austenite is not recognised in the present study because the plane of view is ND. The plate-morphology of austenite is usually observed from RD but the size of the tensile stage hindered this plane of view during the experiment.