Microstructure and Tensile Elongation Enhancement of 1.6 wt% B stainless Steel Plates Fabricated by Composite Rolling

A 3-layered composite plate is innovatively fabricated via composite rolling of 1.6wt% B stainless steel surrounded by two layers of boron-free steels. The tensile properties of composite and non-composite plates are comparatively tested and analyzed. Besides, the microstructure evolution of the investigated plates is characterized in detail. It is found that the composite specimens exhibit higher tensile elongation comparing with that of non-composite specimens. Specifically, the engineering strain of the 1050 degrees Cx30min solution-treated specimens reaches to 12.5 +/- 0.8% which is 2.5-3.0 times as high as that of non-composite specimens. In addition, the as-cast lamellar borides break into bar-shaped structures in hot rolled plates, however, their morphology and distribution hardly change after solution treatment. Besides, the transition regions between the core and clad layers are formed and characterized by medium-sized recrystallized grains and fine borides in the solution-treated composite specimens. The enhancement mechanism of tensile elongation is mainly analyzed in term of the geometrical restriction of necking in the composite plate during tensile deformation. This paper provides a promising method to effectively enhance the tensile fracture elongation for these metallic materials with poor plasticity like high borated stainless steels.