*2.2. Microstructure and Mechanical Properties*

The metallographic samples were parallel to the rolling direction (as Figure 2a shown), and examined with an optical microscope (OM, 4XC-II, Shanghai Optics Instrument Factory Inc., Shanghai, China). The interface microstructure and tensile fracture morphology are observed on scanning electron microscopy (SEM, QUANTA-200, FEI Inc., Hillsboro, OR, USA). The EBSD analysis is performed on a scanning electron microscope (SEM, SIRION 200, FEI Inc., Hillsboro, OR, USA) equipped with an electron backscatter diffraction (EBSD) analyzer (XM4-Hikari, EDAX Inc., Mahwah, NJ, USA). The accelerating voltage was 20 kV, working distance was 10 mm, and the step size of data acquisition was 100 nm. The element distributions near the interface are analyzed with energy dispersive spectroscopy (EDS, GENESIS60S, EDAX Inc., Mahwah, NJ, USA) and electron probe micro-analysis (EPMA, JXA-8230, JEOL Ltd., Tokyo, Japan), respectively. The surfaces in both the TA1 and Q235B were peeled with a mechanical method and characterized by X-ray diffraction (XRD, D/Max 2500, Rigaku Inc., Tokyo, Japan), using Cu Kα radiation scanning range from 30◦ to 90◦ at a step size of 0.02◦.

**Figure 2.** Schematic diagrams of specimen for (**a**) metallographic specimen, (**b**) tensile test, and (**c**) tensile shear test.

The microhardness tests was performed at a Vickers hardness tester (200HVS-5, Huayin Inc., Shandong, China), the load was 19.61 N and the holding time was 10 s. The tensile shear tests and tensile tests were repeated three times on the MTS-810 test machine (MTS Inc., Eden Prairie, MN, USA) at a constant strain rate of 2.5 <sup>×</sup> <sup>10</sup>−<sup>3</sup> <sup>s</sup>−<sup>1</sup> at room temperature (298 K). Moreover, the tensile direction was

parallel to the rolling direction. The size of tensile specimen and the shear specimens (GB/T6396-2008 standard) are shown in Figure 2b,c and the shear strength was calculated by Equation (2).

$$
\pi = \frac{F}{bd} \tag{2}
$$

where *F* is the applied peak force, *b* is the notches distance and *d* is the bonding width of the specimen.
