Fig. 1. Tensile load-displacement curves of the Φ6 mm bars (a) before and after heat treatments: (b) BQ, (c) WQ and (d) SQ.

Fig. 2. Fracture morphology of specimens (a) before and after heat treatments: (b) BQ at 800 °C × 5 min, (c) WQ at 800 °C × 10 min, and (d) SQ at 850 °C × 5 min.

Fig. 3. Microstructures of the Fe-6.5 wt.% Si ally specimens at 300 °C after tensile after heat treatment at 800 °C × 10 min: necking area (a) and homogeneous deformation area (b) after SQ, necking area (c) and homogeneous deformation area (d) after BQ.

Fig. 4. Orientation maps and {112} pole figures of deformation bands and matrix: orientation map (a) and pole figure (b) of a specimen with SQ after 800 °C×10 min; orientation map (c) and pole figure (d) of a specimen with BQ after 800 °C × 10 min.

Fig. 5. TEM images of deformation twins in a specimen with BQ after 800 °C × 10 min: (a) Bright field image shows thin lamellas of twins; (b) Dark field image; (c) Corresponding SAED pattern with a zone axis [113]T. The subscript M stands for the matrix and T for twin.

Fig. 6. Orientation maps of the specimens after SQ at 800 °C×10 min (a), after BQ at 800 °C×10 min (b), and corresponding legend (c) for maps.

Fig. 7. Tensile load-displacement curves of Φ6 mm bars after BQ at 300 °C (a) and at 400 °C (b).

Fig. 8. Tensile load-displacement curves of Φ6 mm bars after heat treatments of BQ (a) and FC (b).

Fig. 9. Relationship between twin stress and grain size: D (a) and 1/√D (b). D represents grain diameter.

Fig. 10. TEM micrographs before deformation of the samples after heat treatment of FC and BQ. After FC: (a) SAED patterns along [011] zone axis, Arrow A designates (200), and arrow B designates (111); (b) Dark field image obtained using (200) spot with arrows designating anti-phase boundary (APB); (c) Dark field image obtained using (111) spot.After BQ: (d) SAED patterns along the [011] zone axis; (e) Dark field image obtained using (200) spot.