a). The formability of high Al lightweight steel is dependent on the
microstructure. The γ-matrix-based high Al steel has better formability
than that of α-matrix-based steel. The α-matrix-based lightweight steel
has high lattice misfit (22.1%) κ-α interface and coarse lamellar structure.
Its cold working formability is low. The γ-matrix-based lightweight
steel has low lattice misfit (2.70%) κ-γ interface and fine
lamellar structure. κ-Carbide in higher Mn steels is much finer than
that in lower Mn steel. This steel shows good formability. The γ-
matrix-based lightweight steel can be obtained by adding more austenite
stabilizing elements, e.g. Mn, or using suitable thermomechanical
processing conditions.