Fig. 1. (a) Schematic of hot-compression bonding process and (b) geometry of tensile test specimens (the red line indicates the position of bonding interface).

Fig. 2. ((a)-(e)) OM images showing microstructural evolution at various strains ((a) 0.11, (b) 0.22, and (c) 0.51) with bonding temperature of 950 °C and various bonding temperatures ((d) 1100 °C and (e) 1200 °C) with strain of 0.51. ((f)-(j)) Corresponding SEM images. In all cases, strain rate was 0.01 s-1 and red arrows indicate bonding interface.

Fig. 3. OM images of interfacial areas of joints formed at strain of 0.51 under high strain rates: (a) 950 °C, $\dot{ε}$= 10 s-1; (b) 950 °C, $\dot{ε}$= 30 s-1; (c) 1100 °C, $\dot{ε}$= 10 s-1; and (d) 1100 °C, $\dot{ε}$= 30 s-1 (red arrows indicate bonding interface).

Fig. 4. Results of EPMA measurements along interfaces of bonded at 950 °C and strain of 0.51 under different strain rates: (a) $\dot{ε}$= 0.01 s-1, (b) $\dot{ε}$= 1 s-1, and (c) $\dot{ε}$= 30 s-1.

Fig. 5. Stress-strain curves and corresponding tensile data for joints bonded at different strain rates and strain of 0.51 at bonding temperatures of (a, c) 950 °C and (b, d) 1100 °C; data for base material are shown for comparison.

Fig. 6. Post-tensile-test fracture surfaces and corresponding macroscopic profiles (inset images) of joints at strain of 0.51: (a)950℃, $\dot{ε}$= 0.01 s-1;(b)950℃, $\dot{ε}$= 10 s-1;(c)950℃, $\dot{ε}$= 30 s-1;(d)1100℃, $\dot{ε}$= 0.01 s-1;(e)1100℃, $\dot{ε}$= 10 s-1;and (f)1100℃, $\dot{ε}$= 30 s-1.

Fig. 7. Orientation imaging microscopy (OIM) maps and corresponding inverse pole figures (IPFs) of joints formed at 950℃ and different strains: (a, b) 0.11, (c, d) 0.22, and (e, f) 0.51. LAGBs (1.5-5°), MAGBs (5-15°), and HAGBs (>15°) are represented by silver, green and black lines, respectively.

Fig. 8. (a) Histogram of misorientation angles at strain of 0.51. (b) Distributions of misorientation angle with increase in strain for sub-boundaries with angles of 1.5-15°.

Fig. 9. OIM maps of joints formed at strain of 0.51 and different strain rates: (a, b) 950℃, $\dot{ε}$= 10 s-1;(c, d) 950℃, $\dot{ε}$= 30 s-1;(e, f)1100℃, $\dot{ε}$= 10 s-1;and (g, h)1100℃, $\dot{ε}$= 30 s-1. LAGBs, MAGBs, and HAGBs are represented by silver, green, and black lines respectively.

Fig. 10. Histogram of misorientation angle under different conditions for strain of 0.51: (a)950℃, $\dot{ε}$= 10 s-1;(b)950℃, $\dot{ε}$= 30 s-1;(c)1100℃, $\dot{ε}$= 10 s-1;and (d)1100℃, $\dot{ε}$= 30 s-1.

Fig. 11. Maps of local misorientation angle and corresponding misorientation profiles along marked line for joints deformed at 950℃ and strain of 0.51 under different strain rates: (a) $\dot{ε}$= 0.01 s-1, (b) $\dot{ε}$= 1 s-1,(c) $\dot{ε}$= 10 s-1, and (d) $\dot{ε}$= 30 s-1.