The effect of loading during martensitic transformation of a maraging steel after prior austenite grain size refinement by thermal cycling

This work demonstrates the efficiency of microstructural tuning by external loading during the martensitic phase transformation of a 12Cr-9Ni-2Mo-0.7Al-0.35Ti maraging steel. Additional prior austenite grain size refinement is achieved by thermal cycling yielding industrially relevant grain sizes, for which not the full set of all 24 characteristic Kurdjumov-Sachs orientation relation variants of martensite is obtained within each grain. For the last thermal cycle three different cases are investigated: i) one specimen is annealed at a higher temperature before the last cooling, ii) one specimen is loaded with a tensile stress of 120 MPa and iii) one specimen with an equivalent 120 MPa Mises stress in torsion during the transformation. This study is one of the first combining the effects of a small grain size, a high dislocation density and external loadings. Orientation imaging microscopy data is presented, revealing the effect of loading type during transformation on the final texture and interface/boundary character.