Microstructure failure in ferrite-martensite dual phase steel under in-situ tensile test

To investigate microstructure failure in ferrite-martensite dual phase steel, in-situ observations were per Micro-fracture formed on multiple plate DP800 specimens during uniaxial tensile tests. Microstructure evolution of the Dual phase steel observed region was investigated in details. The experimental data showed that micro cracks in various re Ferrite gions differed in the initiation time, and micro failures mainly occurred from the locations with typical Martensite characteristics of stress concentration (i. e. ferrite interiors, the interfaces of ferrite-martensite grains and In-situ observation the martensite-martensite interfaces). Growth of micro crack generally experienced the following stages: cracking from martensite boundaries, tiny particles in ferrite interiors, or martensite interiors, propagating in ferrite, bypassing martensite boundaries, or passing through martensite-martensite interfaces, finally ending on martensite boundaries. Martensite was one important source of micro failure and changed the propagation of micro-cracks significantly. Microstructure deformation was inhomogeneous in the stage of plastic deformation.