Enhancement of mechanical properties for quenched and partitioned steels via intragranular austenite

Mechanical properties of quenched and partitioned steels were dramatically enhanced by two types of austenite, including intragranular austenite in ferrite grains and allotriomorphic austenite. The formation mechanism of intragranular austenite as well as its effect on ductility was studied. Digital image correlation strain analyses combined with microstructural observations indicated that most intragranular austenite experienced higher plastic strain than allotriomorphic austenite upon loading, however, intragranular austenite behaved more stable than allotriomorphic austenite, even if both characteristics were very similar. Intragranular austenite in ferrite played a positive role during deformation, like reconciliation of strain, grain refinement as well as transformation-induced plasticity effect. Further adjustment for the amount and stability of intragranular austenite is expected to enhance the ductility of transformation induced plasticity-assisted steels.