Fig. 1 Schematic diagram of the laser melting deposited process

Fig. 2 Detailed schematic diagram of the quenching treatments including DQ and TIQ. *WQ means water quenching, AC means air cooling

Fig. 3 Typical optical micrographs with the insert of scanning electron micrographs showing microstructural evolution of a as-deposited, b DQ-treated and c TIQ-treated specimens

Fig. 4 Combined band contrast and grain boundary outline maps of a DQ-treated and b TIQ-treated specimens

Fig. 5 TEM results of the precipitates inside laths of martensite in the heat-treated specimens: a bright field image of the DQ-treated specimen; b selected area electron diffraction (SAED) pattern corresponding to the circled region in a; c bright field image of the TIQ-treated specimen; d SAED pattern corresponding to the circled region in c

Fig. 6 TEM results of the twins inside laths of martensite in the heat-treated specimens: a bright field image of the DQ-treated specimen; b SAED pattern corresponding to the circle region shown in a; c bright field image of the TIQ-treated specimen; d SAED pattern corresponding to the circle region as shown in c

Fig. 7 Engineering stress-strain curves of the as-deposited, DQ- and TIQ-treated specimens

Fig. 8 Inverse pole figures at the cross-sectional un-deformed areas of a as-deposited, b DQ- and c TIQ-treated tensile specimens, and corresponding Schmid factor maps of the d DQ- and e TIQ-treated tensile specimens

Fig. 9 Kernel average misorientation maps at the cross-sectional uniform-deformed area of a DQ- and b TIQ-treated tensile specimens, and c corresponding histogram of the kernel average misorientation of the DQ- and TIQ-treated specimens

Fig. 10 Microstructures at the cross-sectional necking areas just beneath the fracture surface of a DQ- and b TIQ-treated tensile specimens. (①: micro-voids at the martensite/ferrite interfaces; ②: micro-voids inside martensite)

Fig. 11 Work-hardening curves of the heat-treated specimens